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2024-03-07 22:12:26

YAM中文(简体)翻译：剑桥词典

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yam 在英语-中文（简体）词典中的翻译

yamnoun [ C or U ] uk

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a potato-like root from a tropical climbing plant that can be eaten, or the plant it grows from

薯蓣，山药

US a

sweet potato

甘薯，白薯，红薯，番薯（同 sweet potato）

(yam在剑桥英语-中文（简体）词典的翻译 © Cambridge University Press)

yam的例句

yam

Variability in elephant foot yam following hybridization and open pollination.

来自 Cambridge English Corpus

During the yam growing season, however, which lasted 7 months (including the transitional periods), only 30 conflict cases were documented.

来自 Cambridge English Corpus

On the other hand, that they cultivate yams is itself a culturally transmitted behavior.

来自 Cambridge English Corpus

This is often due to their high ploidy levels (3x for aroids, 6x for yams).

来自 Cambridge English Corpus

Through this practice, pumpkin had a greater influence on the hydrothermal regime of the associated yam before the tubers were harvested.

来自 Cambridge English Corpus

The same observation is true for yam mucilage.

来自 Cambridge English Corpus

Effects of cultivations and heights and directions of staking on yield and general performance of eight yam cultivars.

来自 Cambridge English Corpus

Yam tubers without blemish and about 10 cm in diameter and 20 cm in length were regarded as ware tubers.

来自 Cambridge English Corpus

示例中的观点不代表剑桥词典编辑、剑桥大学出版社和其许可证颁发者的观点。

yam的翻译

中文（繁体）

薯蕷，山藥, 甘薯，白薯，紅薯，番薯（同 sweet potato）…

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西班牙语

ñame, batata, boniato…

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葡萄牙语

inhame, batata doce…

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in Swedish

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in Ukrainian

意大利语

ヤムイモ…

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igname…

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Hint yer elması…

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nyam…

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yam…

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jam…

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yamsrod…

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ubi jalar…

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ต้นมันเทศหรือมันเทศ…

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củ từ…

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(rodzaj słodkiego ziemniaka)…

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jamsrot…

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keladi…

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die Yamswurzel…

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søtpotet, yam(srot)…

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얌, 참마…

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батат…

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igname, yam, (patata dolce)…

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yam, at sweet potato

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“每日一词”

veggie burger

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/ˈvedʒ.i ˌbɜː.ɡər/

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/ˈvedʒ.i ˌbɝː.ɡɚ/

a type of food similar to a hamburger but made without meat, by pressing together small pieces of vegetables, seeds, etc. into a flat, round shape

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在美国留学想吃烤番薯了该买yam还是sweet potato? - 知乎

在美国留学想吃烤番薯了该买yam还是sweet potato? - 知乎首页知乎知学堂发现等你来答切换模式登录/注册美食植物辨识在美国留学想吃烤番薯了该买yam还是sweet potato?关注者8被浏览85,010关注问题写回答邀请回答好问题添加评论分享1 个回答默认排序必填波士顿大学电子工程博士关注自问自答（内附简易食谱）。本来这个问题似乎比较直接，因为番薯（地瓜）就是sweet potato（甜土豆）。然而，前几天烤了番薯，在微信中有人问是yam还是sweet potato。于是，本着科学探索的精神，去了趟超市，买回三个品种的番薯进行研究。下面开始：1. 洗刷干净躺在烤盘上的的番薯们：（烤箱已经预热至425华氏度）这是三个sweet potato, 和所谓的yam们。这次在超市看到了两种yam，以往似乎还见过紫色的。从外表观察，它们似乎都和国内经典小吃，“街边烤番薯”，非常神似。2. 烤好的样子：（放入预热好的烤箱后，烤30分钟，翻面再烤30十分钟。1小时候，光鲜出炉。）表面上看，yam们似乎糖分相对多，体现在渗出的糖汁上。从瘪下去的皮看，sweet potato原先的水分相对少（假设体积减少是因为水分在烧烤时蒸发，且个体水分流失速度一样）。那么，还有什么具体差别吗？聪明的小朋友们马上就要抢答了：“Sweet potato的里面是黄色的，红yam里面是红的，而白yam里面是白的。”我：“。。。好吧，算你们聪明。。。”。。。。。。。。。。。。。。。。。。。。。。。。。。。然而，真相只有一个，而真相是惊人的：3. 烤好剥开的番薯们：矮油，你们是不是眼珠都掉地上了？？？话说，分别试吃之后，我和家中夫人都觉得，sweet potato 们相对纤维多一些，而yam们相对水嫩（不过这也许和我只找到organic/有机yam有关系）。4. 科普：于是开始科普时间：正如抢到沙发的李同学所说，sweet potato 是旋花科(Convolvulaceae，见下面很"旋"的图)番薯属的，而真正的yam是薯蓣科(Dioscoreaceae) 薯蓣属的(包括我们熟知的山药等，详见维基百科Wikipedia)。（旋花科之花，来源：https://zh.wikipedia.org/wiki/%E6%97%8B%E8%8A%B1%E7%A7%91#/media/File:Ipomoea_purpurea1.jpg）而且真正的yam（美国的"真*yam"一般来自加勒比区域）相对番薯们而言，通常含有更多的淀粉和更少的β-胡萝卜素(What Is The Difference Between A Sweet Potato And A Yam? | North Carolina Sweet Potatoes)。它们的表皮也通常像树皮一样粗糙。如果在美国，真正的yam其实是这个样子的：（http://agricnation.com/wp-content/uploads/2016/07/yam-edited-938x535.jpg）所以，回到问题：在美国，想吃烤番薯了，就去超市买你看到像番薯的东西。如果上面写着sweet potato 或者yam，都问题不大。至于怎么烤，就按照上文的方法：1. 烤箱预热至425华氏度；2. 将蕃薯洗干净，并至于烤盘上；3. 放入预热完的烤箱；4. 烤30分钟，翻面再烤30分钟。5. 出炉，小心烫。谢谢大家~鸣谢：sweet potato 三兄弟（老三代出场）红yam白yam编辑于 2017-05-10 13:17赞同 5715 条评论分享收藏喜欢收起

Yam (vegetable) - Wikipedia

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(Top)

1Description

2Etymology

3Distribution and habitat

4Ecology

5Cultivation

Toggle Cultivation subsection

5.1Major cultivated species

5.1.1D. rotundata and D. cayennensis

5.1.2D. alata

5.1.3D. polystachya

5.1.4D. bulbifera

5.1.5D. esculenta

5.1.6D. dumetorum

5.1.7D. trifida

5.2Wild taxa

5.2.1D. hirtiflora subsp. pedicellata

5.2.2D. japonica

5.3Harvesting

5.4Production

6Toxicity

7Uses

Toggle Uses subsection

7.1Nutrition

7.1.1Comparison to other staple foods

7.2Storage

7.3Consumption

7.3.1Africa

7.3.2Brazil

7.3.3Colombia

7.3.4Philippines

7.3.5Vietnam

7.3.6Indonesia

7.3.7Japan

7.3.8India

7.3.9Nepal

7.3.10Fiji Islands

7.3.11Jamaica

7.3.12The West

7.4Phytochemicals and use in medicine

8In culture

Toggle In culture subsection

8.1Nigeria and Ghana

9References

10External links

Toggle the table of contents

Yam (vegetable)

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From Wikipedia, the free encyclopedia

Edible starchy tuber

This article is about the large tuberous starchy root eaten as a staple food. For the sweet potato (Ipomoea batatas), also known as a yam in North America, see Sweet potato. For the oca, the vegetable called yam in New Zealand, see Oxalis tuberosa.

Yams species called Parkistan. The size is for eating but smaller sizes can be cultivated

White yams at a retail market in Brixton, England, 2004

Yam is the common name for some plant species in the genus Dioscorea (family Dioscoreaceae) that form edible tubers (some other species in the genus being toxic).

Yams are perennial herbaceous vines native to Africa, Asia, and the Americas and cultivated for the consumption of their starchy tubers in many temperate and tropical regions. The tubers themselves, also called "yams", come in a variety of forms owing to numerous cultivars and related species.

Description[edit]

A monocot related to lilies and grasses, yams are vigorous herbaceous, perennially growing vines from a tuber.[1] Some 870 species of yams are known,[1] a few of which are widely grown for their edible tuber but others of which are toxic (such as D. communis).

Yam plants can grow up to 15 metres (49 feet) in length and 7.6 to 15.2 centimetres (3 to 6 inches) high.[1] The tuber may grow into the soil up to 1.5 m (5 ft) deep.[1] The plant disperses by seed.[1]

The edible tuber has a rough skin that is difficult to peel but readily softened by cooking. The skins vary in color from dark brown to light pink. The majority, or meat, of the vegetable is composed of a much softer substance ranging in color from white or yellow to purple or pink in mature yams.

Etymology[edit]

The name "yam" appears to derive from Portuguese inhame or Canarian Spanish ñame, which derived from Fula, one of the West African languages during trade.[2] However, in Portuguese, this name commonly refers to the taro plant (Colocasia esculenta) from the genus Colocasia, as opposed to Dioscorea.[3][4]

The main derivations borrow from verbs meaning "to eat".[2] True yams have various common names across multiple world regions.[1]

In some places, other (unrelated) root vegetables are sometimes referred to as "yams", including:[1]

In the United States, sweet potatoes (Ipomoea batatas), especially those with orange flesh, are often referred to as "yams"[5][6]

In Australia, the tubers of the Microseris lanceolata, or yam daisy, were a staple food of Aboriginal Australians in some regions.[7]

In New Zealand, oca (Oxalis tuberosa) is typically referred to as "yam".[8][9]

In Malaysia and Singapore, taro (Colocasia esculenta) is referred to as "yam".[10]

In Africa, South and Southeast Asia as well as the tropical Pacific islands Amorphophallus paeoniifolius is grown and known as "elephant foot yam".[11]

Distribution and habitat[edit]

Yams are native to Africa, Asia, and the Americas.[1] Three species were independently domesticated on those continents: D. rotundata (Africa), D. alata (Asia), and D. trifida (South America).[12]

Ecology[edit]

Some yams are invasive plants, often considered a noxious weed outside cultivated areas.[1]

Cultivation[edit]

Freshly harvested purple yam (D. alata) sliced for cross-section

Yams are cultivated for the consumption of their starchy tubers in many temperate and tropical regions, especially in West Africa, South America and the Caribbean, Asia, and Oceania.[1] About 95% of yam crops are grown in Africa.[13]

A yam crop begins when whole seed tubers or tuber portions are planted into mounds or ridges, at the beginning of the rainy season. The crop yield depends on how and where the sets are planted, sizes of mounds, interplant spacing, provision of stakes for the resultant plants, yam species, and tuber sizes desired at harvest. Small-scale farmers in West and Central Africa often intercrop yams with cereals and vegetables. The seed yams are perishable and bulky to transport. Farmers who do not buy new seed yams usually set aside up to 30% of their harvest for planting the next year. Yam crops face pressure from a range of insect pests and fungal and viral diseases, as well as nematode. Their growth and dormant phases correspond respectively to the wet season and the dry season. For maximum yield, the yams require a humid tropical environment, with an annual rainfall over 1,500 millimetres (59 in) distributed uniformly throughout the growing season. White, yellow, and water yams typically produce a single large tuber per year, generally weighing 5 to 10 kilograms (11 to 22 pounds).[14]

Yams suffer from relatively few pests and diseases.[15] There is an anthracnose caused by Colletotrichum gloeosporioides which is widely distributed around the world's growing regions.[15] Winch et al., 1984 finds C. gloeosporioides afflicts a large number of Dioscorea spp.[15]

Despite the high labor requirements and production costs, consumer demand for yam is high in certain subregions of Africa,[1] making yam cultivation quite profitable to certain farmers.[citation needed]

Major cultivated species[edit]

Many cultivated species of Dioscorea yams are found throughout the humid tropics.[1] The most economically important are discussed below.[14]

Non-Dioscorea tubers that were historically important in Africa include Plectranthus rotundifolius (the Hausa potato) and P. esculentus (the Livingstone potato); these two tuber crops have now been largely displaced by the introduction of cassava.[16]

D. rotundata and D. cayennensis[edit]

D. rotundata, the white yam, and D. cayennensis, the yellow yam, are native to Africa. They are the most important cultivated yams. In the past, they were considered as two separate species, but most taxonomists now regard them as the same species. Over 200 varieties between them are cultivated.[citation needed]

White yam tuber is roughly cylindrical in shape, the skin is smooth and brown, and the flesh is usually white and firm. Yellow yam has yellow flesh, caused by the presence of carotenoids. It looks similar to the white yam in outer appearance; its tuber skin is usually a bit firmer and less extensively grooved. The yellow yam has a longer period of vegetation and a shorter dormancy than white yam.

The Kokoro variety is important in making dried yam chips.[17]

They are large plants; the vines can be as long as 10 to 12 m (33 to 39 ft). The tubers most often weigh about 2.5 to 5 kg (6 to 11 lb) each, but can weigh as much as 25 kg (55 lb). After 7 to 12 months' growth, the tubers are harvested. In Africa, most are pounded into a paste to make the traditional dish of "pounded yam", known as Iyan.[18]

D. alata[edit]

Water yam (D. alata)

D. alata, called purple yam (not to be confused with the Okinawan purple "yam", which is a sweet potato), greater yam, ube, winged yam, water yam, and (ambiguously) white yam,[19][1] was first cultivated in Southeast Asia.[1] Although not grown in the same quantities as the African yams, it has the largest distribution worldwide of any cultivated yam, being grown in Asia, the Pacific islands, Africa, and the West Indies.[1] Even in Africa, the popularity of water yam is second only to white yam. The tuber shape is generally cylindrical, but can vary. Tuber flesh is white and watery in texture.

D. alata and D. esculenta (lesser yam) were important staple crops to the seafaring Austronesian cultures. They were carried along with the Austronesian migrations as canoe plants, from Island Southeast Asia to as far as Madagascar and Polynesia.[20][21][22][23]

D. polystachya[edit]

Chinese yam (D. polystachya)

D. polystachya, Chinese yam, is native to China. The Chinese yam plant is somewhat smaller than the African, with the vines about 3 m (10 ft) long. It is tolerant to frost and can be grown in much cooler conditions than other yams. It is also grown in Korea and Japan.

It was introduced to Europe in the 19th century, when the potato crop there was falling victim to disease, and is still grown in France for the Asian food market.

The tubers are harvested after about 6 months of growth. Some are eaten right after harvesting and some are used as ingredients for other dishes, including noodles, and for traditional medicines.[18]

D. bulbifera[edit]

Air potato (D. bulbifera)

Wild yam (D. sp.)

D. bulbifera, the air potato, is found in both Africa and Asia, with slight differences between those found in each place. It is a large vine, 6 m (20 ft) or more in length. It produces tubers, but the bulbils which grow at the base of its leaves are the more important food product. They are about the size of potatoes (hence the name "air potato"), weighing from 0.5 to 2.0 kg (1 lb 2 oz to 4 lb 7 oz).

Some varieties can be eaten raw, while some require soaking or boiling for detoxification before eating. It is not grown much commercially since the flavor of other yams is preferred by most people. However, it is popular in home vegetable gardens because it produces a crop after only four months of growth and continues producing for the life of the vine, as long as two years. Also, the bulbils are easy to harvest and cook.[18]

In 1905, the air potato was introduced to Florida and has since become an invasive species in much of the state. Its rapid growth crowds out native vegetation and it is very difficult to remove since it can grow back from the tubers, and new vines can grow from the bulbils even after being cut down or burned.[24]

D. esculenta[edit]

Wild bitter vines (D. dumetorum)

D. esculenta, the lesser yam, was one of the first yam species cultivated. It is native to Southeast Asia and is the third-most commonly cultivated species there, although it is cultivated very little in other parts of the world. Its vines seldom reach more than 3 m (10 ft) in length and the tubers are fairly small in most varieties.

The tubers are eaten baked, boiled, or fried much like potatoes. Because of the small size of the tubers, mechanical cultivation is possible, which along with its easy preparation and good flavor, could help the lesser yam to become more popular in the future.[18]

D. dumetorum[edit]

D. dumetorum, the bitter yam, is popular as a vegetable in parts of West Africa, in part because their cultivation requires less labor than other yams. The wild forms are very toxic and are sometimes used to poison animals when mixed with bait. It is said[according to whom?] that they have also been used for criminal purposes.[18]

D. trifida[edit]

D. trifida, the cush-cush yam, is native to the Guyana region of South America and is the most important cultivated New World yam. Since they originated in tropical rainforest conditions, their growth cycle is less related to seasonal changes than other yams. Because of their relative ease of cultivation and their good flavor, they are considered to have a great potential for increased production.[18]

Wild taxa[edit]

D. hirtiflora subsp. pedicellata[edit]

D. hirtiflora subsp. pedicellata, lusala, busala or lwidi, is native to Tropical Africa. It is widely harvested and eaten in Southern Zambia where it grows in open forest areas. In Southern Zambia, it is an important addition to the March–September diets of almost all, and income of over half of rural households.[25] Research on propagation of this subspecies to alleviate the threat from wild harvest has been successful.[26]

D. japonica[edit]

D. japonica – known as East Asian mountain yam, yamaimo, or Japanese mountain yam – is a type of yam (Dioscorea) native to Japan (including Ryukyu and Bonin Islands), Korea, China, Taiwan, and Assam.

D. japonica is used for food. Jinenjo, also called the wild yam, is a related variety of Japanese yam that is used as an ingredient in soba noodles.

Harvesting[edit]

Tile on street depicting Aboriginal women gathering yams. Cooktown, Australia. 2005

Yams in West Africa are typically harvested by hand, using sticks, spades, or diggers.[27] Wood-based tools are preferred to metallic tools as they are less likely to damage the fragile tubers; however, wood tools need frequent replacement. Yam harvesting is labor-intensive and physically demanding. Tuber harvesting involves standing, bending, squatting, and sometimes sitting on the ground depending on the size of mound, size of tuber, or depth of tuber penetration. Care must be taken to avoid damage to the tuber, because damaged tubers do not store well and spoil rapidly. Some farmers use staking and mixed cropping, a practice that complicates harvesting in some cases.

In forested areas, tubers grow in areas where other tree roots are present. Harvesting the tuber then involves the additional step of freeing them from other roots. This often causes tuber damage.

Aerial tubers or bulbils are harvested by manual plucking from the vine.

Yields may improve and cost of yam production be lower if mechanization were to be developed and adopted. However, current crop production practices and species used pose considerable hurdles to successful mechanization of yam production, particularly for small-scale rural farmers. Extensive changes in traditional cultivation practices, such as mixed cropping, may be required. Modification of current tuber harvesting equipment is necessary given yam tuber architecture and its different physical properties.[27]

Production[edit]

Further information: Yam production in Nigeria

Yam production - 2020

Country

Production(millions of tonnes)

Nigeria

50.1

Ghana

8.5

Ivory Coast

7.7

Benin

3.2

Togo

0.9

Cameroon

0.7

World

74.8

Source:UN Food and Agriculture Organization[28]

In 2020, world production of yams was 75 million metric tons (74,000,000 long tons; 83,000,000 short tons), led by Nigeria with 67% of the total (table).

Toxicity[edit]

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Unlike cassava, most varieties of edible, mature, cultivated yam do not contain toxic compounds. However, there are exceptions. Bitter compounds tend to accumulate in immature tuber tissues of white and yellow yams. These may be polyphenols or tannin-like compounds.[citation needed]

Wild forms of bitter yams (D. dumetorum) do contain some toxins, such as dihydrodioscorine, that taste bitter, hence are referred to as bitter yam.[29] Bitter yams are not normally eaten except at times of desperation in poor countries and in times of local food scarcity. They are usually detoxified by soaking in a vessel of salt water, in cold or hot fresh water or in a stream. The bitter compounds in these yams are water-soluble alkaloids which, on ingestion, produce severe and distressing symptoms. Severe cases of alkaloid intoxication may prove fatal.[citation needed]

Aerial or potato yams (D. bulbifera) have antinutritional factors. In Asia, detoxification methods, involving water extraction, fermentation, and roasting of the grated tuber, are used for bitter cultivars of this yam. The bitter compounds in yams also known locally as air potato include diosbulbin and possibly saponins, such as diosgenin.[30] In Indonesia, an extract of air potato is used in the preparation of arrow poison.[31]

Uses[edit]

Nutrition[edit]

Yam, rawNutritional value per 100 g (3.5 oz)Energy494 kJ (118 kcal)Carbohydrates27.9 gSugars0.5 gDietary fiber4.1 g

Fat0.17 g

Protein1.5 g

VitaminsQuantity %DV†Vitamin A equiv.1% 7 μgThiamine (B1)10% 0.112 mgRiboflavin (B2)3% 0.032 mgNiacin (B3)0.552 mgPantothenic acid (B5)6% 0.314 mgVitamin B623% 0.293 mgFolate (B9)6% 23 μgVitamin C21% 17.1 mgVitamin E2% 0.35 mgVitamin K2% 2.3 μg

MineralsQuantity %DV†Calcium2% 17 mgIron4% 0.54 mgMagnesium6% 21 mgManganese19% 0.397 mgPhosphorus8% 55 mgPotassium27% 816 mgZinc3% 0.24 mg

"Link to USDA Database entry".

Units

μg = micrograms • mg = milligrams

IU = International units

†Percentages are roughly approximated using US recommendations for adults. Source: USDA FoodData Central

Raw yam has only moderate nutrient density, with appreciable content (10% or more of the Daily Value, DV) limited to potassium, vitamin B6, manganese, thiamin, dietary fiber, and vitamin C (table).[32] But raw yam has the highest potassium levels amongst the 10 major staple foods of the world (see nutritional chart). Yam supplies 118 calories per 100 grams. Yam generally has a lower glycemic index, about 54% of glucose per 150 gram serving, compared to potato products.[33]

The protein content and quality of roots and tubers is lower than other food staples, with the content of yam and potato being around 2% on a fresh-weight basis. Yams, with cassava, provide a much greater proportion of the protein intake in Africa, ranging from 5.9% in East and South Africa to about 15.9% in humid West Africa.[34]

As a relatively low-protein food, yam is not a good source of essential amino acids. Experts emphasize the need to supplement a yam-dominant diet with more protein-rich foods to support healthy growth in children.[35][36]

Yam is an important dietary element for Nigerian and West African people. It contributes more than 200 calories per person per day for more than 150 million people in West Africa, and is an important source of income. Yam is an attractive crop in poor farms with limited resources. It is rich in starch, and can be prepared in many ways. It is available all year round, unlike other, unreliable, seasonal crops. These characteristics make yam a preferred food and a culturally important food security crop in some sub-Saharan African countries.[37]

Comparison to other staple foods[edit]

The following table shows the nutrient content of yam and major staple foods in a raw harvested form on a dry weight basis to account for their different water contents. Raw forms, however, are not edible and cannot be digested. These must be sprouted, or prepared and cooked for human consumption. In sprouted or cooked form, the relative nutritional and antinutritional contents of each of these staples is remarkably different from that of raw form of these staples.[citation needed]

Nutrient content of 10 major staple foods per 100 g dry weight[38]

Staple

Maize (corn)[A]

Rice, white[B]

Wheat[C]

Potatoes[D]

Cassava[E]

Soybeans, green[F]

Sweet potatoes[G]

Yams[Y]

Sorghum[H]

Plantain[Z]

RDA

Water content (%)

Raw grams per 100 g dry weight

111

114

115

476

250

313

435

333

110

286

Nutrient

Energy (kJ)

1698

1736

1574

1533

1675

1922

1565

1647

1559

1460

8,368–10,460

Protein (g)

10.4

8.1

14.5

9.5

3.5

40.6

7.0

5.0

12.4

3.7

Fat (g)

5.3

0.8

1.8

0.4

0.7

21.6

0.2

0.6

3.6

1.1

44–77

Carbohydrates (g)

130

Fiber (g)

8.1

1.5

14.0

10.5

4.5

13.1

13.0

13.7

6.9

6.6

Sugar (g)

0.7

0.1

0.5

3.7

4.3

0.0

18.2

1.7

0.0

42.9

minimal

Minerals

[A]

[B]

[C]

[D]

[E]

[F]

[G]

[Y]

[H]

[Z]

RDA

Calcium (mg)

616

130

1,000

Iron (mg)

3.01

0.91

3.67

3.71

0.68

11.09

2.65

1.80

4.84

1.71

Magnesium (mg)

141

145

110

203

109

106

400

Phosphorus (mg)

233

131

331

271

606

204

183

315

700

Potassium (mg)

319

131

417

2005

678

1938

1465

2720

385

1426

4700

Sodium (mg)

239

1,500

Zinc (mg)

2.46

1.24

3.05

1.38

0.85

3.09

1.30

0.80

0.00

0.40

Copper (mg)

0.34

0.25

0.49

0.52

0.25

0.41

0.65

0.60

0.23

0.9

Manganese (mg)

0.54

1.24

4.59

0.71

0.95

1.72

1.13

1.33

2.3

Selenium (μg)

17.2

81.3

1.4

1.8

4.7

2.6

2.3

0.0

4.3

Vitamins

[A]

[B]

[C]

[D]

[E]

[F]

[G]

[Y]

[H]

[Z]

RDA

Vitamin C (mg)

0.0

93.8

51.5

90.6

10.4

57.0

0.0

52.6

Thiamin (B1) (mg)

0.43

0.08

0.34

0.38

0.23

1.38

0.35

0.37

0.26

0.14

1.2

Riboflavin (B2) (mg)

0.22

0.06

0.14

0.13

0.56

0.26

0.10

0.15

0.14

1.3

Niacin (B3) (mg)

4.03

1.82

6.28

5.00

2.13

5.16

2.43

1.83

3.22

1.97

Pantothenic acid (B5) (mg)

0.47

1.15

1.09

1.43

0.28

0.47

3.48

1.03

0.74

Vitamin B6 (mg)

0.69

0.18

0.34

1.43

0.23

0.22

0.91

0.97

0.86

1.3

Folate Total (B9) (μg)

516

400

Vitamin A (IU)

238

563

4178

460

3220

5000

Vitamin E, alpha-tocopherol (mg)

0.54

0.13

1.16

0.05

0.48

0.00

1.13

1.30

0.00

0.40

Vitamin K1 (μg)

0.3

0.1

2.2

9.0

4.8

0.0

7.8

8.7

0.0

2.0

120

Beta-carotene (μg)

108

36996

277

1306

10500

Lutein+zeaxanthin (μg)

1506

253

6000

Fats

[A]

[B]

[C]

[D]

[E]

[F]

[G]

[Y]

[H]

[Z]

RDA

Saturated fatty acids (g)

0.74

0.20

0.30

0.14

0.18

2.47

0.09

0.13

0.51

0.40

minimal

Monounsaturated fatty acids (g)

1.39

0.24

0.23

0.00

0.20

4.00

0.00

0.03

1.09

0.09

22–55

Polyunsaturated fatty acids (g)

2.40

0.20

0.72

0.19

0.13

10.00

0.04

0.27

1.51

0.20

13–19

[A]

[B]

[C]

[D]

[E]

[F]

[G]

[Y]

[H]

[Z]

RDA

A raw yellow dent corn

B raw unenriched long-grain white rice

C raw hard red winter wheat

D raw potato with flesh and skin

E raw cassava

F raw green soybeans

G raw sweet potato

H raw sorghum

Y raw yam

Z raw plantains

/* unofficial

Storage[edit]

Roots and tubers such as yam are living organisms. When stored, they continue to respire, which results in the oxidation of the starch (a polymer of glucose) contained in the cells of the tuber, which converts it into water, carbon dioxide, and heat energy. During this transformation of the starch, the dry matter of the tuber is reduced.

Amongst the major roots and tubers, properly stored yam is considered to be the least perishable. Successful storage of yams requires:[31][39]

initial selection of sound and healthy yams

proper curing, if possible combined with fungicide treatment

adequate ventilation to remove the heat generated by respiration of the tubers

regular inspection during storage and removal of rotting tubers and any sprouts that develop

protection from direct sunlight and rain

Storing yam at low temperature reduces the respiration rates. However, temperatures below 12 °C (54 °F) cause damage through chilling, causing a breakdown of internal tissues, increasing water loss and yam's susceptibility to decay. The symptoms of chilling injury are not always obvious when the tubers are still in cold storage. The injury becomes noticeable as soon as the tubers are restored to ambient temperatures.

The best temperature to store yams is between 14 and 16 °C (57 and 61 °F), with high-technology-controlled humidity and climatic conditions, after a process of curing. Most countries that grow yams as a staple food are too poor to afford high-technology storage systems.

Sprouting rapidly increases a tuber's respiration rates, and accelerates the rate at which its food value decreases.[31]

Certain cultivars of yams store better than others. The easier to store yams are those adapted to arid climate, where they tend to stay in a dormant low-respiration stage much longer than yam breeds adapted to humid tropical lands, where they do not need dormancy. Yellow yam and cush-cush yam, by nature, have much shorter dormancy periods than water yam, white yam, or lesser yam.

Storage losses for yams are very high in Africa, with bacteria, insects, nematodes, and mammals being the most common storage pests.[40]: 12-7

Consumption[edit]

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Yams being fried in Ivory Coast

Yams are consumed in a variety of preparations, such as flour or whole vegetable pieces across their range of distribution in Asia, Africa, North America, Central America, the Caribbean, South America, and Oceania.[1]

Africa[edit]

TongaPounding yam, DR Congo

Yams of African species must be cooked to be safely eaten, because various natural substances in yams can cause illness if consumed raw. The most common cooking methods in Western and Central Africa are by boiling, frying or roasting.[41]

Among the Akan of Ghana, boiled yam can be mashed with palm oil into eto in a similar manner to the plantain dish matoke, and is served with eggs. The boiled yam can also be pounded with a traditional mortar and pestle to create a thick, starchy paste known as iyan (pounded yam) which is eaten with traditional sauces such as egusi and palm nut soup.[citation needed]

Another method of consumption is to leave the raw yam pieces to dry in the sun. When dry, the pieces turn a dark brown color. These are then milled to create a brown powder known in Nigeria as elubo. The powder can be mixed with boiling water to create a thick starchy paste, a kind of pudding known as amala, which is then eaten with local soups and sauces.[citation needed]

Yams are a staple agricultural commodity in West Africa with cultural significance,[41] where over 95% of the world's yam crop is harvested. Yams are still important for survival in these regions. Some varieties of these tubers can be stored up to six months without refrigeration, which makes them a valuable resource for the yearly period of food scarcity at the beginning of the wet season. Yam cultivars are also cultivated in other humid tropical countries.[1]

Yam is the main staple crop of the Igbos in south eastern Nigeria where for centuries it played a dominant role in both their agricultural and cultural life. It is celebrated with annual yam festivals.[citation needed]

Brazil[edit]

Yams are particularly consumed in the coastal area of the Northeast region, although they can be found in other parts of the country. In Pernambuco state, it is usually boiled and served cut in slices at breakfast, along with cheese spread or molasses.[citation needed]

Colombia[edit]

In Colombia yam production has been specifically located in the Caribbean region, where it has become a key product in the diet of the population of this area. In 2010, Colombia was among the 12 countries with the highest yam production worldwide, and ranked first in yield of tons per hectare planted. Although its main use is for food, several studies have shown its usefulness in the pharmaceutical industry and the manufacture of bioplastics. However, in Colombia, there is no evidence of the use of this product, other than food.[42]

Philippines[edit]

Yams at Port-Vila market (Vanuatu)

A piece of cake made with ube (purple yam; Philippines)

In the Philippines, the purple ube species of yam (D. alata), is eaten as a sweetened dessert called ube halaya, and is also used as an ingredient in another Filipino dessert, halo-halo. It is also used as a popular ingredient for ice cream.[citation needed]

Vietnam[edit]

In Vietnam, the same purple yam is used for preparing a special type of soup canh khoai mỡ or fatty yam soup. This involves mashing the yam and cooking it until very well done. The yam root was traditionally used by peasants in Vietnam to dye cotton clothes throughout the Red River and Mekong delta regions as late as the mid-20th century, and is still used by others in the Sapa region of northern Vietnam.[43]

Indonesia[edit]

In Indonesia, the same purple yam is used for preparing desserts. This involves mashing the yam and mixing it with coconut milk and sugar. White- and off-white-fleshed yams are cut in cubes, cooked, lightly fermented, and eaten as afternoon snacks.[citation needed]

Japan[edit]

Yamakake, Japanese dish prepared from tororo (D. polystachya) and maguro (tuna)

An exception to the cooking rule is the mountain yam (Dioscorea polystachya), known as nagaimo and can be further classified into ichōimo (lit. 'ginkgo-leaf yam'; kanji: 銀杏芋), or yamatoimo (lit. Yamato yam; kanji: 大和芋), depending on the root shape.[citation needed]

Mountain yam is eaten raw and grated, after only a relatively minimal preparation: the whole tubers are briefly soaked in a vinegar-water solution to neutralize irritant oxalate crystals found in their skin. The raw vegetable is starchy and bland, mucilaginous when grated, and may be eaten plain as a side dish, or added to noodles.[citation needed]

Another variety of yam, jinenjo, is used in Japan as an ingredient in soba noodles. In Okinawa, purple yams (Dioscorea alata) are grown. This purple yam is popular as lightly deep-fried tempura, as well as being grilled or boiled. Additionally, the purple yam is a common ingredient of yam ice cream with the signature purple color. Purple yam is also used in other types of traditional wagashi sweets, cakes, and candy.[citation needed]

India[edit]

In central parts of India, the yam is prepared by being finely sliced, seasoned with spices, and deep fried. In Southern India, the vegetable is a popular accompaniment to rice dishes and curry. The purple yam, D. alata, is also eaten in India, where it is also called the violet yam. Species may be called by the regional name "taradi", which can refer to D. belophylla,[44] Dioscorea deltoidea,[45] and D. bulbifera.[46] Digging and selling taradi is a major source of income in the region of Palampur.[47]

Nepal[edit]

Dioscorea root is traditionally eaten on Māgh Sankrānti (a midwinter festival) in Nepal. It is usually steamed and then cooked with spices.[citation needed]

Fiji Islands[edit]

Yam[48] is, along with cassava and taro, a staple food, and is consumed boiled, roasted in a lovo, or steamed with fish or meat in curry sauce or coconut milk and served with rice. The cost of yam is higher due to the difficulty in farming and relatively low volume of production.[48]

Jamaica[edit]

Because of their abundance and importance to survival, yams were highly regarded in Jamaican ceremonies and constitute part of many traditional West African ceremonies.[49]

The West[edit]

Yam powder is available in the West from grocers specializing in African products, and may be used in a similar manner to instant mashed potato powder, although preparation is a little more difficult because of the tendency of the yam powder to form lumps. The powder is sprinkled onto a pan containing a small amount of boiling water and stirred vigorously. The resulting mixture is served with a heated sauce, such as tomato and chili, poured onto it.

Skinned and cut frozen yams may also be available from specialty grocers.

Phytochemicals and use in medicine[edit]

The tubers of certain wild yams, including a variant of 'Kokoro' yam and other species of Dioscorea, such as Dioscorea nipponica, are a source for the extraction of diosgenin, a sapogenin steroid.[30] The extracted diosgenin is used for the commercial synthesis of cortisone, pregnenolone, progesterone, and other steroid products.[50] Such preparations were used in early combined oral contraceptive pills.[51] The unmodified steroid has estrogenic activity.[52]

In culture[edit]

1817 painting of Ashanti yam ceremony, Ghana

Historical records in West Africa and of African yams in Europe date back to the 16th century. Yams were taken to the Americas through precolonial Portuguese and Spanish on the borders of Brazil and Guyana, followed by a dispersion through the Caribbean.[53]

Yams are used in Papua New Guinea, where they are called kaukau. Their cultivation and harvesting is accompanied by complex rituals and taboos. The coming of the yams (one of the numerous versions from Maré) is described in Pene Nengone (Loyalty Islands of New Caledonia).[citation needed]

Nigeria and Ghana[edit]

A yam festival is usually held in the beginning of August at the end of the rainy season. People offer yams to gods and ancestors first, before distributing them to the villagers. This is their way of giving thanks to the spirits above them.[citation needed]

The New Yam Festival celebrates the main agricultural crop of the Igbos, Idomas, and Tivs. The New Yam Festival, known as Orureshi in Owukpa in Idoma west and Ima-Ji, Iri-Ji or Iwa Ji in Igbo land, is a celebration depicting the prominence of yam in social and cultural life. The festival is prominent among southeastern states and major tribes in Benue State, mainly around August.[citation needed]

The Igbo people accord special respect to yam to the extent that no one eats the newly harvested yam until the New Yam celebrations / feast is marked. It is called Iri ji ọhụrụ. People return to their various communities for the celebrations.[citation needed]

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^ "Yam production in 2019". Crops/Regions/World/Production Quantity. FAOSTAT, Statistics Division of the UN Food and Agriculture Organization. 2021. Retrieved 12 October 2021.

^ Dioscorea dumetorum: Useful Tropical Plants

^ a b Jesus, M.; Martins, A. P; Gallardo, E.; Silvestre, S. (2016). "Diosgenin: Recent highlights on pharmacology and analytical methodology". Journal of Analytical Methods in Chemistry. 2016: 1–16. doi:10.1155/2016/4156293. PMC 5225340. PMID 28116217.

^ a b c Oke, O.L. (1990). Redhead, J.; Hussain, M.A. (eds.). Roots, tubers, plantains and bananas in human nutrition. United Nations Food and Agriculture Organization. ISBN 978-92-5-102862-9.

^ Uwaegbute, Osho and Obatolu (1998). Postharvest technology and commodity marketing: Proceedings of a postharvest conference. International Institute of Tropical Agriculture. p. 172. ISBN 978-978-131-111-6.

^ "Glycemic index and glycemic load for 100+ foods". Harvard Health Publications. Harvard Medical School. 2008.

^ "Roots, tubers, plantains and bananas in human nutrition - Nutritive value". United Nations Food and Agriculture Organization. Retrieved 25 May 2020.

^ "Kwashiorkor (Protein-Calorie Malnutrition)". Tropical Medicine Central Resource. 2006.

^ "Undernutrition". The Merck Manual: The Home Health Handbook. 2010.

^ OB Izekor; MI Olumese (December 2010). "Determinants of yam production and profitability in Edo State, Nigeria" (PDF). African Journal of General Agriculture. 6 (4). Archived from the original (PDF) on 17 May 2017.

^ "Nutrient data laboratory". United States Department of Agriculture. Retrieved 10 August 2016.

^ Roots, Tubers, and Plantains in Food Security: In Sub-Saharan Africa, in Latin America and the Caribbean, in the Pacific. United Nations Food and Agriculture Organization. 1989. ISBN 978-92-5-102782-0.

Robertson, Gordon; Lupien, John (2008). "Minimizing Postharvest Losses in Yam (Dioscorea spp.): Treatments and Techniques". Using food science and technology to improve nutrition and promote national development: Selected case studies. International Union of Food Science & Technology. S2CID 107695924.

^ a b Nweke, Felix; Aidoo, Robert; Okoye, Benjamin (July 2013). "Yam Consumption Patterns in West Africa". Bill and Melinda Gates Foundation. Retrieved 5 December 2017.

^ "El cultivo de ñame en el Caribe colombiano". Banco de la República, Colombia. 21 June 2012.

^ Yam Root Dye

^ Singh, K.K. and Kaushal Kumar. Ethnobotanical wisdom of Gaddi tribe in Western Himalaya. 2000. p.18.

^ Rana, M., Kabra, A., Kabra, R., Rana, M. and Dhatwalia, V. 2015. Plant Species used by locals as Ethano - Medicine in Gohar Tehsil, Distt. Mandi Region of North Western Himalaya. PharmaTutor. 3, 4 (Apr. 2015), 47-52.

^ Rajendra, Gupta (1993). "Conservation and utilization of Indian Medicinal Plants". Indian Journal of Plant Genetic Resources. 6 (2). ISSN 0971-8184. Retrieved 16 September 2021.

^ Dr. Chiranjit Parmar, in article "Taradi", The Heirloom Gardener, 2007.

^ a b Naleba, Mere (25 April 2015). "Million dollar aim". The Fiji Times Online. Retrieved 1 June 2017.

^ Goody, Jack (1996). Cooking, cuisine and class: A study in comparative sociology. Cambridge University Press. pp. 78–81. ISBN 978-0-521-28696-1.

^ Marker RE, Krueger J (1940). "Sterols. CXII. Sapogenins. XLI. The Preparation of Trillin and its Conversion to Progesterone". Journal of the American Chemical Society. 62 (12): 3349–3350. doi:10.1021/ja01869a023.

^ Djerassi, C. (December 1992). "Steroid research at Syntex: "the pill" and cortisone". Steroids. 57 (12): 631–641. doi:10.1016/0039-128X(92)90016-3. PMID 1481227. S2CID 5933910.

^ Liu MJ, Wang Z, Ju Y, Wong RN, Wu QY (2005). "Diosgenin induces cell cycle arrest and apoptosis in human leukemia K562 cells with the disruption of Ca2+ homeostasis". Cancer Chemotherapy and Pharmacology. 55 (1): 79–90. doi:10.1007/s00280-004-0849-3. PMID 15372201. S2CID 11779821.

^ United Nations Food and Agriculture Organization. "Roots, tubers, plantains and bananas in human nutrition". Acknowledgments, preface, introduction, origins, and distribution.

External links[edit]

Look up yam in Wiktionary, the free dictionary.

"Yam crop improvement". International Institute for Tropical Agriculture.

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An underutilized orphan tuber crop—Chinese yam : a review

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AbstractMain conclusionThe diversification of food crops can improve our diets and address the effects of climate change, and in this context the orphan crop Chinese yam shows significant potential as a functional food.AbstractAs the effects of climate change become increasingly visible even in temperate regions, there is an urgent need to diversify our crops in order to address hunger and malnutrition. This has led to the re-evaluation of neglected species such as Chinese yam (Dioscorea polystachya Turcz.), which has been cultivated for centuries in East Asia as a food crop and as a widely-used ingredient in traditional Chinese medicine. The tubers are rich in nutrients, but also contain bioactive metabolites such as resistant starches, steroidal sapogenins (like diosgenin), the storage protein dioscorin, and mucilage polysaccharides. These health-promoting products can help to prevent cardiovascular disease, diabetes, and disorders of the gut microbiome.

Whereas most edible yams are tropical species, Chinese yam could be cultivated widely in Europe and other temperate regions to take advantage of its nutritional and bioactive properties. However, this is a laborious process and agronomic knowledge is fragmented. The underground tubers contain most of the starch, but are vulnerable to breaking and thus difficult to harvest. Breeding to improve tuber shape is complex given the dioecious nature of the species, the mostly vegetative reproduction via bulbils, and the presence of more than 100 chromosomes. Protocols have yet to be established for in vitro cultivation and genetic transformation, which limits the scope of research. This article summarizes the sparse research landscape and evaluates the nutritional and medical applications of Chinese yam. By highlighting the potential of Chinese yam tubers, we aim to encourage the adoption of this orphan crop as a novel functional food.

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IntroductionGrains and vegetables provide a rich source of calories and nutrients, but many people subsist on monotonous cereal diets and are therefore nutritionally deprived even if they ingest sufficient calories. Increasing the diversity of crops on global and local markets is one of the major challenges for agriculture, especially in the face of climate change (Hunter et al. 2019; Mabhaudhi et al. 2019). So-called orphan crops are underutilized species that have local significance, especially for small-scale farmers, but are neglected on a global scale (Mabhaudhi et al. 2019). They are often overlooked by researchers, despite valuable traits that are promising for emerging markets (Tadele 2019). Orphan crops offer greater nutritional value that could improve and diversify our diets (Hunter et al. 2019). Some of them also have potential as functional foods and could capture new markets (Aditya et al. 2019). One such orphan crop is the Chinese yam, Dioscorea polystachya Turcz. The tubers of this crop are highly nutritious but they also contain health-promoting secondary metabolites that provide additional health benefits such as the regulation of blood sugar levels and the control of cholesterol, fat uptake and hypertension (Chen et al. 2003; Shujun et al. 2008; Amat et al. 2014; Zhang et al. 2016). These properties reflect the high content of resistant starches, polysaccharides, and steroidal sapogenins, which could allow the development of Chinese yam as a functional food for the prevention of diabetes and heart disease. The tubers can be prepared in the same way as potatoes, or can be used as a food additive. Chinese yam is a well-known vegetable in East Asia, especially in China where it has been used as food and in traditional medicine for thousands of years (Amat et al. 2014), but it is almost unknown to the rest of the world. Several yam species have become staple foods in West Africa, but Chinese yam is the only edible yam species that can be cultivated in temperate regions such as Europe. However, the cultivation of this crop is challenging, which has hampered its commercial development beyond East Asia. In this review, we highlight the unique properties of Chinese yam tubers, as well as discussing the genetics, breeding options and cultivation of this orphan crop. We also evaluate the potential of Chinese yam as a functional food for global markets, based on its cultivation in temperate regions.Global relevance and cultivation of yam speciesYams (Dioscorea spp.) are distributed almost ubiquitously in the tropics and subtropics but few species can grow in temperate regions (Wilkin et al. 2005). Yams are cultivated as food crops in Africa, Asia, parts of South America and the Caribbean, and in the South Pacific islands (Asiedu and Sartie 2010). However, yam cultivation in other places may not been reported, so these statistics may not provide the full picture of the geographical scope of yam cultivation. Production is concentrated in Nigeria, Ghana, Benin, the Republic of Côte d’Ivore, Cameroon and Togo, which together comprise the so called ‘yam belt’ (Scarcelli et al. 2019). In these countries, yams are not only staple foods but also have important cultural and social functions (Obidiegwu and Akpabio 2017).Nigeria tops the list of producers, with almost 48 million tonnes harvested in 2018 (FAOSTAT). Global production has increased dramatically over the last 20 years, starting from ~ 17 million tonnes in 1988 to reach 73 million tonnes in 2018 (FAOSTAT). This partially reflects the efforts of organizations such as the International Institute of Tropical Agriculture (IITA), which focuses on maximizing the profitability of yam production (Mignouna et al. 2009). Despite its growing importance, research on yam crops has been neglected for a long time and modern breeding programs based on genomics have been applied to yams only in the last few years (Darkwa et al. 2019).Chinese yam is unusual in that it is indigenous to temperate regions and tolerates much colder temperatures than its relatives. The species is native to China, Korea, the Kuril Islands and Taiwan, but has been introduced into Japan, the south-east USA, Uruguay and Western Himalaya (Coursey 1967a; POWO 2019). In China, it is called ‘Huai Shan Yao’ (Zhang et al. 2011). In Japan, Chinese yam cultivars are distinguished by tuber shape, namely Nagaimo (cylindrical), Tsukuneimo (round) and Ichoimo (flattened) (Babil et al. 2013). Here we use the binomial designation Dioscorea polystachya Turcz., but various synonyms are used in the literature, including D. batatas, D. pseudobatatas, D. rosthornii and D. swinhoei, which often leads to confusion and disagreement (Ting and Gilbert 2000; Hsu et al. 2013). In East Asian literature, the species is usually named D. opposita Thunb., but according to the ‘world checklist of selected plant families’ this is now regarded as a synonym for D. oppositifolia, a yam species native to India (Kew Science; Ting and Gilbert 2000). Furthermore, D. esuclenta and D. bulbifera are known as ‘Chinese yam’ in some regions, whereas the name ‘cinnamon vine’ typically refers to D. polystachya Turcz. but is also used for other yam species in the Americas, increasing the degree of confusion (Coursey 1967a). For clarity, we use Chinese yam to mean Dioscorea polystachya Turcz. throughout this article. The closely related Japanese yam (D. japonica Thunb.) is native to South China, Japan, Korea and Taiwan (Kew Science; Hsu et al. 2013). In Japan it is called ‘yamanoimo’ (Kawasaki et al. 2001). This species can also grow in temperate climates and is widely cultivated as a food crop, and the review also covers some studies that focus on this species.Several cultivars of Chinese yam are grown for food and medical purposes (Kawasaki et al. 2014). The Henan province in China is the main production area and is associated with the highest quality products (Zhang et al. 2014). In China, the cultivar ‘Tiegun’ is most popular because it has superior nutritional and pharmaceutical properties and has been used to treat conditions such as diarrhea, diabetes and asthma for more than 2000 years (Peng et al. 2017). In China, producers are currently unable to meet the high demand for this valuable product (Zhang et al. 2014). Depending on the cultivar, Chinese yam tubers comprise ~ 65% starch, ~ 9% protein and ~ 1.2% fiber, and also provide a rich source of minerals (e.g., ~ 470 mg/kg Ca and Mg) and bioactive compounds such as allantoin and dioscin, which account for 0.8% and 0.077% of the dry weight, respectively (Wu et al. 2016). In contrast to other edible yams, Chinese yam tubers are non-toxic and can be eaten raw (Chan and Ng 2013). The peel is usually removed, and the remaining flesh has a sticky texture reflecting the high quantity of mucilage, which is appreciated in East Asia because it lends texture to soup.Botanical and physiological propertiesThe family Dioscoreaceae includes > 650 species in 4 genera, including the large yam genus Dioscorea with about 625 species (Caddick et al. 2002; Wilkin et al. 2005; POWO 2019). Within this genus the Chinese yam belongs to the section Enantiophyllum, which includes two important food staples: the water yam D. alata and the white guinea yam D. rotundata (Coursey 1967a; Wilkin et al. 2005; Govaerts et al. 2007; Viruel et al. 2016). Phylogenetic analysis using complete chloroplast genome sequences show that these three species are closely related within the section Enantiophyllum (Fig. 1). Yams are monocotyledonous twining vines that use other plants for support, and their stems can climb to a height of > 3 m (Coursey 1967a, b; Mueller et al. 2003). Some yam species form starchy underground tubers and sometimes aerial tubers (bulbils) in their leaf axils, which are used for propagation (Ding and Gilbert 2000). This has facilitated their domestication for food and medical use (Coursey 1967a). They grow annually and the tubers enter a long phase of dormancy at the end of the season before they re-sprout. This prolonged dormancy allows wild yams to be used as a famine food in West Africa (Martin and Degras 1978). Most yam plants are dioecious, meaning that male pistil-bearing flowers and female stamina-bearing flowers form on separate plants, although occasionally monoecious and non-flowering cultivars can be found (Coursey 1967a). Yam flowers are small (2–4 mm in diameter) and are thought to be naturally pollinated by thrips and other small insects (Coursey 1967a; Segnou et al. 1992; Mizuki et al. 2005a). Chinese yam plants flower between June and September, with fruit set between July and November (Ting and Gilbert 2000). Yam fruits are trilocular capsules, 1–3 cm in length, that contain small, light and flattened seeds (Coursey 1967a). True seeds are produced when male and female plants grow in close proximity, but clonal reproduction and vegetative propagation are far more common (Mizuki et al. 2010; Walck et al. 2010). In its natural habitat, the Chinese yam grows in forests, on mountain slopes, and along rivers and roadsides (Ting and Gilbert 2000).Fig. 1Phylogenetic tree based on the complete chloroplast genome sequences of 9 Dioscorea species. Maximum likelihood (ML) topology shown with ML bootstrap support values/Bayesian posterior probability listed at each node. Dioscorea species were grouped into clade A and B. Figure taken from (Zhao et al. 2018)Full size imageYam genetics is poorly understood because most yam species are polyploid with a long growth cycle, infrequent flowering, a heterozygous genetic background, and predominant vegetative propagation (Mignouna et al. 2003). Species of the genus Dioscorea show high variation of ploidy levels among and within species (Gamiette et al. 1999; Dansi et al. 2001; Obidiegwu et al. 2009; Viruel et al. 2019). The most common food yams have ploidy levels of 4 × and 6 × for D. alata (Viruel et al. 2019), 4×, 6 × and 8 × for D. cayenensis/D. rotundata complex (Dansi et al. 2001; Obidiegwu et al. 2009; Viruel et al. 2019) and 2 × and 8 × for D. bulbifera (Viruel et al. 2019). Reported base numbers include x = 6, 7, 9, 10 and 20 (x = number of chromosomes per single monoploid genome) with x = 10 being the most common base number among cultivated species (Martin and Ortiz 1963; Viruel et al. 2008; Arnau et al. 2009). For Chinese yam and D. japonica a base number of x = 10 with chromosome numbers of 2n = 100 or 140 for Chinese yam (Babil et al. 2013; Viruel et al. 2019) and 2n = 40, 80 and 100 for D. japonica have been reported (Nakajima 1934; Araki et al. 1983).Tuber anatomy and growthYam tubers have unique morphological and physiological characteristics (Onwueme 1979). Whereas the storage organs of most root and tuber crops originate from the roots (sweet potato and cassava), stem (potato) or corm (taro), yam tubers are derived from the hypocotyl (Lawton and Lawton 1969; Shewry 2003). The tubers of Chinese yam feature a thin brown skin made of cork cells that covers the inner white flesh (Raman et al. 2014). Small roots on the tuber surface confer a hairy appearance (Coursey 1967a). The skin comprises several cork layers and a band of lignified sclerenchymal cells. The cork cambium features two layers of tangentially elongated parenchymal cells and the cortex consists of compact cells arranged in 6–8 layers. The ground tissue is wide and filled with starch grains, with a small number of irregularly distributed vascular bundles. Many idioblasts containing calcium oxalate embedded in mucilage are distrusted in the cortex and ground tissue. The starch grains are oval, elliptic or shell-shaped, 10–39 µm long and 7–29 µm wide (Raman et al. 2014).The tubers of Chinese yam are usually spindle-shaped or club-like, and may grow up to a meter in length, but they are comparatively thin (ca. 5–8 cm (Araki et al. 1983)) and grow almost vertically (in the direction of gravity), resembling the growth of a primary root (Coursey 1967a; Kawasaki et al. 2008). Harvesting is therefore labor-intensive because the tubers must be dug out of the ground while avoiding damage. In Japan, the tubers are often cultivated in horizontal pipes that protect them, guide their growth, and facilitate harvesting (Kadota and Niimi 2004). However, the tuber shape is cultivar-dependent, in some cases thin and elongated, and in others thicker, flattened or even oval, with the latter being easier to harvest (Kawasaki et al. 2008; Babil et al. 2013). The tuber shape depends on factors such as the density, porosity and chemical properties of the soil, and the presence of obstacles in the soil (which lead to deformation). Chinese yam tubers grow only at the tip, which contains apical meristem that proliferates continually while the upper tuber part enters dormancy, creating a tuber with a thin top and a thick base. The tuber tip exhibits positive gravitropism, and amyloplasts in the tip undergo sedimentation along the gravity vector, suggesting they serve as gravity-sensing statoliths that guide tuber formation (Kawasaki et al. 2008). Additional gravistimulation experiments revealed that only the subapical part of the tubers shows a response to gravity. This is similar to the distal elongation zone near root caps, where the curvature response occurs after gravistimulation (Kawasaki et al. 2014). The gravisensing site in the tuber tip may change during tuber growth in some cultivars. For example, tuber growth in the cultivar Genkotsujirou is thought to switch between elongation and thickening phases, whereas most cultivars remain in the elongation phase. In cultivars that feature a thickening phase, the tuber tip possesses fewer amyloplasts indicating a loss of gravisensing ability (Kawasaki et al. 2008). Gravistimulation experiments in which tubers were reoriented showed that the tuber tip finds its way back to the gravity vector by changing the direction of growth. This was accompanied by changes in amyloplast localization, supporting their role in gravisensing and tuber growth. Interestingly, changing the tuber orientation in short intervals caused the tuber to grow several tips that extended in different directions (Kawasaki et al. 2014). To suppress shoot production by gravitropic disorientation, this may be connected to upside-down or vertical storage practices of yam tubers (Coursey 1967b).Life cycle and cultivationYams that are used as field crops are basically perennial plant, but are often cultivated annually (Coursey 1967a). Tubers and bulbils can be used as propagation organs (Kim et al. 2003a). If Chinese yam plants are grown from bulbils, the resulting tubers are small but can be used as set seed in the 2nd year. When large tuber pieces or whole tubers are used for seed setting, the new tubers can exceed 1 m in length and weigh more than 3 kg. In the northern hemisphere, Chinese yam sets are usually planted in spring and grow over the summer months until they start to wilt in autumn. Tubers and bulbils are dormant at maturity, and cold stratification is required for germination in the following spring (Okagami and Tanno 1991). The growth of tropical and temperate edible yams is in principle similar and occurs in four phases (Asiedu et al. 1998; Gong et al. 2017), which are shown for Chinese yam in Fig. 2.Fig. 2Growth cycle of Chinese yam. a: Young tuber 25 days after emergence. b: Bud at a tuber head. c: Bulbils in leaf axils. d: Female inflorescence. e: Starch granules in the tuber stele. f: Male inflorescence. g: Seed capsules. h: Mature tuberFull size imagePhase I: initiation (March–April)The life cycle starts when the new plant emerges from the post-dormant tuber. The physiological processes involved in tuber sprouting have been well described in several Dioscorea species (Lawton and Lawton 1969). In contrast to potato, yam tubers do not produce dormant buds. Instead, sprouting involves the activity of a layer of meristematic cells located just beneath the tuber skin (Onwueme 1973; Wickham et al. 1981). One or a few buds are formed de novo just before sprouting, usually in the head region first because sprouting yam tubers exhibit proximal dominance (Onwueme 1979). This is caused by a gradient in the level of dormancy: the tuber tip proliferates continually but the head region enters dormancy, thus the dormancy period starts earlier and there is less time between harvest and sprouting. When the first sprouts form, the formation of subsequent sprouts is repressed. The tuber heads are therefore preferred as seed tubers because they will sprout earlier than the middle and tail regions. This is important for yam multiplication because cutting the tuber into segments just before planting will lead to heterogeneous and delayed sprouting, reflecting the need for the middle or tail parts to differentiate into new buds. For African yam, multiplication techniques such as minisetting with small tuber pieces have been developed to overcome the otherwise low multiplication rates (Onwueme 1973,1979; Aighewi et al. 2015).The sprout becomes visible as a swollen structure known as the primary nodal complex, from which the yam vines, feeder roots, and the new tuber emerge (Hamadina 2012). Tuber initiation is characterized by rapid proliferation of the meristematic tissue at the junction between the stem and root, which soon forms an organized structure with a set proximal-to-distal (head-to-tail) polarity. The distal end is geotropic and grows downwards, whereas the proximal end hardens (Asiedu et al. 1998). The timing of tuber initiation depends on the species and environmental factors (Asiedu et al. 1998). In Chinese yam, tuber initiation begins as early as 20 days after the field planting of tuber pieces with buds (Gong et al. 2017). Upon further growth, the old tuber shrivels as it supplies the new plant with nutrients (Asiedu et al. 1998).Phase II: enlargement (May–September)Phase II is characterized by rapid cell division and expansion. The vine elongates, leaves expand, and tubers enlarge (Asiedu et al. 1998). Later in this phase, bulbils and flowers can be produced. The development of bulbils in Chinese yam plants is dependent on the cultivar, but the ability to flower is dependent on the size of the seed tuber. Depending on the cultivar, the minimum weight for floral initiation is 40–75 g (Yoshida et al. 1996). This is relevant for breeding because plants that grow from bulbils or true seeds tend not to flower in the first year.During the enlargement phase, Chinese yam tubers grow slowly for 40–60 days, then enter a rapid growth period lasting ~ 60 days before leveling off and reaching a plateau over the next ~ 30 days (Onwueme 1979). During the early stages of the rapid growth period, the tuber increases significantly in length and to a lesser extent in width and weight (Gong et al. 2017). At the end of this phase, the maximum canopy is reached and the tubers rapidly accumulate dry matter. Here, the maximum tuber yield is determined by the rate of photosynthesis and translocation of assimilates from source tissues (Asiedu et al. 1998). The tuber does not accumulate starch during the initiation phase but starch grains are formed in the parenchymal cells during the enlargement phase, leading to rapid starch accumulation. Enzymes related to sugar metabolism and starch biosynthesis are upregulated during the enlargement phase, and the tuber also accumulates the storage protein dioscorin (Luo et al. 2018).Phase III: maturation (October–November)Phase III is characterized by photoperiod-dependent senescence of the leaf canopy, a decline in the accumulation of dry matter, and tuber maturation (Asiedu et al. 1998). Tuber cell size and starch accumulation reach maximum values during phase III (Luo et al. 2018). The end of tuber growth is accompanied by senescence of the stem and foliage, and the onset of complete tuber dormancy (Gong et al. 2017). Bulbils, if present, also reach their maximum size and enter dormancy at this point.Phase IV: dormancyFor Chinese yam tubers and bulbils, the dormant phase lasts ~ 3 months and cold storage is required before dormancy is broken (Hashimoto et al. 1972; Okagami and Tanno 1991). The long dormancy phase allows cultivated yam tubers to be kept in prolonged storage. During storage, the tubers lose dry weight and moisture and undergo biochemical changes such as the loss of starch and the accumulation of the reducing sugars maltose and fructose (Hariprakash and Nambisan 1996). The characteristics of dormancy are well described in tropical edible yam species and the mechanisms have been extensively discussed elsewhere (Craufurd et al. 2001; Ile et al. 2006).Factors that influence tuber growthThe enlargement of yam tubers is influenced by the photoperiod. For example short-day (SD) conditions promote the enlargement of water yam tubers whereas long-day (LD) conditions have the opposite effect (Vaillant et al. 2005). Likewise, SD conditions (10-h days) promote tuber enlargement in Chinese yam, but only during the initial growth stage (Yoshida and Kanahama 1999; Chen et al. 2010). SD conditions inhibit tuber enlargement when the rapid growth phase is complete (Shiwachi et al. 2000). Furthermore, Chinese yam tuber growth is not limited to SD conditions, but continues (albeit more slowly) under LD conditions (Shiwachi et al. 2000). In the Chinese yam cultivar Nagaimo, SD conditions (8-h days) in the early to middle growth period produced larger new tubers (and bulbils) compared to LD (24-h light) conditions, but the tuber weight at harvest in December was the same in plants grown under LD and SD conditions (Yoshida et al. 2001; 2002).Tuberization and tuber enlargement in Chinese yam seem to be controlled by plant hormones. For example, the endogenous concentration of biologically active gibberellins is related to tuber enlargement, increasing during tuber growth and reaching a peak at the beginning of the rapid growth phase (after 90 days). After that, gibberellin levels decline to low levels at the end of the growth phase (Gong et al. 2017). Accordingly, exogenous gibberellins can increase tuber yields (Yoshida et al. 2001, 2002; Kim et al. 2003b). However, gibberellins suppress bulbil formation, and the application of growth retardants such as mepiquat chloride (an inhibitor of gibberellin synthesis) can induce early bulbil formation and increase bulbil size in variety Tsukune (Yoshida et al. 2002; Kim et al. 2003a). These results indicate that underground tubers and aerial bulbils are regulated by different hormonal mechanisms. Breeding for larger and more abundant bulbils is important because the bulbils can only be used for propagation if they reach a certain size (Kim et al. 2003a).The endogenous concentrations of other plant hormones also change during tuber growth: endogenous cytokinins and jasmonates accumulate during tuber enlargement and become depleted again during tuber maturation (Gong et al. 2017). Endogenous levels of the auxin indole-3-acetic acid (IAA) increase during tuber enlargement and reach a peak during the rapid growth stage. The concentration then declines during the late growth stage before increasing again, reaching a second peak during the maturation stage. The first peak may correlate with the induction of cell division by IAA during tuber enlargement, whereas the second may correlate with enhanced starch accumulation, although this has not been experimentally confirmed. Endogenous concentrations of abscisic acid (ABA) increase during the early stages of tuber enlargement and then decline continuously (Gong et al. 2017).Plant hormones also influence tuber dormancy in Chinese yam (Hashimoto et al. 1972; Hasegawa and Hashimoto 1973). Batatasins are abundant in mature tubers but levels decline during prolonged storage (Kim et al. 2002). Exogenous gibberellins induce and extend dormancy in Chinese yam, suggesting that endogenous gibberellins participate in the induction and maintenance of dormancy (Okagami and Nagao 1971; Tanno et al. 1992; Okagami and Tanno 1993). Accordingly, sprouting is inhibited by the application of gibberellins and is promoted by gibberellin inhibitors (Okagami and Nagao 1971). The mechanisms behind the dual role of gibberellins in tuber enlargement and dormancy are not yet understood (Gong et al. 2017). Interestingly, gibberellins appear to have opposing functions in yam and potato tubers, given that gibberellins are required to break dormancy in potato (Hartmann et al. 2011; Rentzsch et al. 2012) but extend dormancy in cultivated yams (Okagami and Tanno 1993; Craufurd et al. 2001).Current research status and breeding objectivesChina has domesticated several species of yam for food and medical purposes (Coursey 1967a; Wu et al. 2014) and there are 14 major cultivars of Chinese yam in Chinese market (Peng et al. 2017). Little is known about the genetics and genetic diversity of Chinese yam, although this knowledge would be invaluable for breeding approaches (Cao et al. 2018). Several molecular markers have been developed to study population diversity and to distinguish among cultivars, which is difficult to achieve using morphological characteristics alone (Mizuki et al. 2005b, 2010; Wu et al. 2014; Peng et al. 2017; Cao et al. 2018). Molecular markers are necessary to identify landraces and to prevent the misidentification of medical yam cultivars in China (Wu et al. 2014). Intron sequence amplified polymorphism (ISAP) and sequence characterized amplified region (SCAR) markers were therefore used to discriminate among the 14 major cultivars in China, leading to the identification of a marker specific for the most popular cultivar ‘Tiegun’, which is the sole source of tuber material used in traditional Chinese medicine (Peng et al. 2017). The authors detected high genetic diversity among these cultivars by ISAP profiling, which was explained by the domestication of yam driven by traditional farmers, who select for a broad range of traits. Favored varieties were therefore maintained and genetic erosion of the species was avoided (Peng et al. 2017). In the same study, ISAP markers were associated with morphological characteristics, including tuber and leaf shape (Peng et al. 2017). Recently, the chloroplast genomes of six Chinese yam cultivars were compared to develop new markers for genetic studies (Cao et al. 2018). Reference genome sequences have been published for D. rotundata and D. dumetorum (Tamiru et al. 2017; Siadjeu et al. 2020). A pre-publication genome sequence for D. alata is also available (Dioscorea alata v2.1 DOE-JGI, https://phytozome.jgi.doe.gov/) and preliminary analysis of the D. zingiberensis genome has been reported (Zhou et al. 2018) but was not yet made publicly available while this manuscript was in preparation. In addition, a bait kit to obtain genomic data for Dioscorea sp. has been designed improving the data situation for yam genotyping and phylogenetic comparison efforts (Soto Gomez et al. 2019). These assets indicate a growing interest in yam genetics although a genome sequence for D. polystachya is not yet available.There have been few reports describing the molecular characterization of yam proteins in planta (Liu et al. 2017; Chen et al. 2019b). Genetic transformation has been successful in D. rotundata and D. zingiberensis (Zhu et al. 2009; Shi et al. 2012; Nyaboga et al. 2014) but the only transgenic yam line reported thus far is a D. zingiberensis mutant generated using the CRISPR/Cas9 system to reduce the expression of farnesyl pyrophosphate synthase mRNA, resulting in the depletion of squalene (Feng et al. 2018). The transformation of Chinese yam was recently confirmed, but the process is currently inefficient and must be optimized before routine applications are possible (Junhua et al. 2019). Micropropagation has been used to generate Chinese yam microtubers in tissue culture, which are useful to avoid the carryover of viruses during long-term vegetative propagation (Nagasawa and Finer 1989; Kohmura et al. 1995; Kadota and Niimi 2004; Li et al. 2014). Reference genes suitable for quantitative expression analysis have also been identified to enable further molecular studies (Zhao et al. 2016).Several genes involved in storage organ development have been identified in potato and other tuberous crops (Navarro et al. 2011, 2015; Kloosterman et al. 2013; Lee et al. 2013). It is not yet clear if these genes also play a role in yam. Transcriptome analysis to compare tubers during initiation and expansion revealed several differentially expressed genes that may be involved in tuber expansion (Zhou et al. 2020). These included genes related to MAP kinase signaling, starch and sucrose metabolism, hormone biosynthesis and signaling, as well as transcription factors and miRNAs involved in these processes (Zhou et al. 2020).Research is gathering pace in tropical yam species (Darkwa et al. 2019) but, as discussed above, breeding is hindered by the long growth cycle, dioecious reproduction, limited flowering, vegetative propagation, extensive polyploidy, and heterozygous genetic background (Mignouna et al. 2007). Crossing is also inefficient because fruiting is rare in female plants and the capsules often contain no seeds (Yakuwa et al. 1981). High temperatures (30 °C) have a positive effect on pollen germination and elongation, and hot summers could therefore promote seed setting in Chinese yam (Araki et al. 1981). Pollen from the cultivar Nagaimo can germinate and elongate in vitro, suggesting that impaired pollen germination cannot explain the lack of fruit and seed setting (Araki et al. 1981). Most research on Chinese yam currently takes place in East Asia, and many articles are published only in Chinese language journals without international access. These linguistic and technical barriers limit the global awareness of this crop and hamper research to improve its cultivation.Opportunities for the global cultivation of Chinese yamChinese yam was already used by humans in China during the Neolithic period: archaeological excavations at Xinglonggou confirm it was used as early as ~ 6200–5200 BC (Liu et al. 2015). There is further evidence from an archaeological site at Shuidonggou indicating its use as early as ~ 30,000 BC, during the Upper Paleolithic period (Guan et al. 2014). The species was fully domesticated ~ 1000 years ago (Peng et al. 2017) and was introduced into Europe as a potential alternative to potato during the Great Famine in Ireland caused by potato blight (Kühn 1855). Nowadays, Chinese yam is mostly unknown in Europe and is cultivated only in France near Orleans (O’Sullivan 2010) and in Germany near lake Constance. Comparatively high yields of 20 t/ha can be achieved in these regions based on FAOSTAT data from 2017 (Lebot 2019). More widespread cultivation is limited by the need for support during growth (Chinese yam is cultivated as an annual climber) and the lack of mechanical automated tuber-harvesting systems (Lebot 2019). Because the tubers of Chinese yam are delicate and become deformed when they encounter obstacles in the soil, it is important to identify candidate sites with optimal growth conditions. The Chinese yam is susceptible to various viruses including the Japanese yam mosaic virus (Fuji and Nakamae 1999; Mochizuki et al. 2017), Yam mild mosaic virus (Fuji et al. 2001), Chinese yam necrotic mosaic virus (Fukumoto and Tochihara 1978) and Broad bean wilt virus 2 (Kondo et al. 2005). Leaf miners (Acrolepiopsis spp.) and root-knot nematodes have been reported to cause damage to Chinese yam cultivated in Japan (QianKui et al. 2000; Yasuda 2000; Tanaka et al. 2001). It can be assumed that related biotic stresses will also affect cultivation of Chinese yam in other regions of the world.The most suitable areas in China are the flat landscapes in northern Shaanxi, eastern Shandong, and eastern Hebei, with specific soil parameters including a rich supply of minerals and a loose structure that allows the cultivation of fragile tubers (Fan et al. 2019). Although Chinese yam can be grown in humus or loess soil, sandy soil is preferable because it increases the polysaccharide and glucose content of the tubers (Ma et al. 2019). Warmer climates accelerate growth, and climate change may therefore make these areas even more suitable in the future, presumably reflecting the higher photosynthetic rate in response to elevated CO2 levels, leading to more leaf and tuber biomass under summer and autumn conditions, respectively (Thinh et al. 2017). The regions in China best suited for the cultivation of Chinese yam have also been predicted by spatial modeling using geographic information systems (Hu et al. 2018). This highlighted areas such as the lower reaches of the Yellow River basin and the North China Plain, mainly in north-eastern Henan, in the Hebei and Shandong provinces, largely in agreement with the results of soil analysis (Fan et al. 2019). In addition to the flat terrain and soil composed of loose, mineral-rich river sediments, these regions have an annual mean temperature of ~ 14 °C, an annual precipitation of 581 mm and ~ 2300 h of sunshine per year.Applications and innovations derived from Chinese yamAs well as providing staple foods, yams are also used as functional foods and medicines. In this context, the rare ability of Chinese yam to grow in temperate regions is an advantage (Rinaldo 2020). China is currently the major exporter of Chinese yam products, followed by Mexico and the USA (https://www.tridge.com/intelligences/chinese-yam, retrieved on 02/11/2020). Europe holds a minor share of this market because Chinese yam products are also exported from France, but Europe as a whole is a major importer, with the UK, Netherlands, France and Germany all ranked among the top 10 importers. Globally, the top three importers are the USA, Japan and the UK. Patents mentioning Chinese yam reflect these market shares, with most published and registered in the US but with assignees in China or other parts of South East Asia (data not shown). The companies with the most patents/patent applications are L’Oreal (France), Standard Foods (Taiwan) and Sumitomo Chemicals (Japan). As discussed in more detail below, yam (Dioscorea sp.) tubers can also be used as a source of medicines or precursor compounds that are converted into drugs. For example, diosgenin and other steroids extracted from D. villosa or D. composita are used to synthesize pharmaceutically relevant derivatives such as cortisone (Lubbe and Verpoorte 2011). The importance of such applications is highlighted by Syntex Corporation (Panama), a company acquired by Roche in 1994 for more than US$ 5 billion (https://www.crunchbase.com/organization/syntex). The use of Chinese yam in traditional Chinese medicine was mentioned in the Shennong Bencaojing (The Classic of Herbal Medicine) first as a wild species, but almost exclusively in cultivated form for the last ~ 400 years (Cheng et al. 2014). The number of research publications and patents concerning Chinese yam has risen quickly over the last 20 years (Fig. 3). Most of the patents refer to food or medical uses, but there are also patents describing harvesting machines (Aixin et al. 2004), mechanical seed dispensers (Ledermann and Stufflebeam 1998), agricultural chemicals (Hashimoto et al. 1979; Hayashi et al. 2009) and tissue culture techniques for in vitro propagation (Takayama and Akita 1991).Fig. 3The increasing interest in Chinese yam over the last 20 years based on scientific publications and patents. a Annual number of scientific publications and patents referring to Chinese yam in title, abstract and/or keywords/claims (TS/CTB = (“Dioscorea polystachya” OR “shan yao” OR “shanyao” OR “iron yam” OR “Dioscorea batatas” OR “Dioscorea japonica” OR “Dioscorea decaisneana” OR “Dioscorea doryphora” OR “Dioscorea swinhoei” OR “Dioscorea rosthornii” OR “Dioscorea potaninii” OR “Dioscorea pseudobatatas” OR “Dioscorea opposita” OR “Dioscorea oppositifolia” OR “D. polystachya” OR “D. batatas” OR “D. japonica” OR “D. decaisneana” OR “D. doryphore” OR “D. swinhoei” OR “D. rosthornii” OR “D. potaninii” OR “D. pseudobatatas” OR “D. opposite” OR “D. oppositifolia” OR “Chinese yam” OR “cinnamon-vine” OR “Chinese potato” OR “nagaimo”); please note: given the confusion in the botanical nomenclature of the D. polystachya, our search term may include patents not necessarily referring to Chinese yam but other species as well. We have screened the patents; however we cannot guarantee that the true species accounted for is Chinese yam in every case) (publications from Web of Science since 1948; patents from Derwent World Patents Index (DWPI) since 1920). b Application fields based on international patent classification (IPC) codes, inner circle, for Chinese yamFull size imageChinese yam ingredients with health benefits and other useful propertiesChinese yam tubers can be used directly as vegetables for cooking, but the starchy flour is also used for baking and for the preparation of noodles (Wang 2019; Nakagawa 2019; Li et al. 2020). The tubers not only provide calories and nutrients, but also contain various bioactive secondary metabolites that are likely to underlie the use of this species in traditional Chinese medicine and in modern herbal remedies (Perera and Li 2012). Chinese yam tubers and extracts have been shown to reduce serum levels of low-density lipoprotein (LDL) cholesterol and inhibit fat absorption in rodents, alleviating hypertension and attenuating obesity caused by a high-fat diet (Chen et al. 2003; Kwon et al. 2003; Liu et al. 2009; Amat et al. 2014; Gil et al. 2015). There is also evidence that the tubers reduce the incidence of diabetes (Gao et al. 2007; Hsu et al. 2007; Fan et al. 2015; Li et al. 2017), possibly reflecting their ability to inhibit α-glucosidase activity (Zhang et al. 2011). Chinese yam tubers are rich in antioxidants (Chiu et al. 2013) and have a positive effect on the immune system (Choi et al. 2004; Hou and Jin 2012) which is probably linked to their ability to modulate inflammation (Jin et al. 2011; Gil et al. 2015). Anti-tumor and prebiotic effects have also been reported (Huang et al. 2012; Liu et al. 2019; Zhang et al. 2019). Patents claiming pharmaceutical properties or health benefits have been approved for several Chinese yam extracts (Kotani et al. 2010; Nam et al. 2010; Kim et al. 2019) and powders (Wang et al. 2019). The ingredients with pharmacological activity are mainly polysaccharides (such as resistant starches), as well as sapogenins (especially diosgenin) and the storage protein dioscorin (Perera and Li 2012), which are discussed in turn below.StarchesStarch is the most abundant component of Chinese yam tubers and is the primary calorific constituent (as is the case for potato and cassava). Patents in this category include the use of Chinese yam starch to produce flours for instant noodles (Lometillo and Wolcott 1983) and animal feed such as horse biscuits (Naji and Nerys 1999). Other patents in the area of ‘medical and veterinary science’ indicate the potential utilization of Chinese yam starch as a functional food, including a drink ingredient that is purported to activate stem cell growth (Weng and Wu 2016).Approximately 85% of the starch produced by Chinese yam plants is stored in the underground tubers for vegetative re-sprouting (Zhang et al. 2014, 2018), representing ~ 67% of the total dry weight of the tuber (Zhou et al. 2012; Zhang et al. 2018). Most of the rest is stored in the bulbils (Zhou et al. 2012; Zhang et al. 2018). The bulbil starch has greater swelling power, solubility in water and viscosity than tuber starch, and also greater thermostability and resistance to hydrolysis, reflecting the higher amylose content of 38% in bulbils compared to 35% in tubers (Zhang et al. 2018; Zhou et al. 2012). The amylose content is much higher than that found in other edible yam species, such as D. rotundata and D. alata, where the tubers contain 26% and 21% starch, respectively (Riley et al. 2004; 2014). The properties of Chinese yam starch are also cultivar dependent. For example, D. opposita cv. Baiyu starch has the lowest amylose content and the highest degree of crystallinity whereas D. opposita cv. Jiaxiangxichangmao starch has the highest amylose content and lowest degree of crystallinity (Shujun et al. 2006). As these results show, the degree of crystallinity is an indicator for the amylose content while the crystallinity type refers additionally to the amylopectin chain length (Cheetham and Tao 1998). Thus, high crystallinity (CA and CC) are suggesting a higher amylopectin content however with a lower chain length and is positively influencing the resistance of starch against degrading enzymes (Cheetham and Tao 1998; Raigond et al. 2015). Both CA (Zhang et al. 2018) and CB (Shunjun et al. 2006) crystallinity patterns have been reported, and type CC (a mixture of both) is likely to occur in Chinese yam tubers and bulbils (Shujun et al. 2008; Jiang et al. 2012). These results suggest a certain degree of amylopectin in Chinese yam tubers and bulbils. However only amylose content was directly measured yet, while a chemical determination of the starch composition is, to the best of our knowledge, still unavailable (Zhang et al. 2018; Chen et al. 2019a). The properties of Chinese yam starch could potentially be altered by the genetic modification of starch branching enzymes to favor amylose biosynthesis (Ma et al. 2018; Wang et al. 2018). Chinese yam starch shows higher gelatinization efficiency but a lower swelling potential compared to potato and maize starch (Shujun et al. 2008; Jiang et al. 2011). Chinese yam starch is stored mainly in amyloplasts, where (as discussed above) the starch granules influence gravitropism and thus tuber shape and growth (Kawasaki et al. 2001; 2008, 2014). Starch biosynthesis is therefore a valuable target for breeding strategies seeking to improve the nutritional, functional and/or developmental traits of Chinese yam.The quality of extracted Chinese yam starch also varies with tuber freshness and drying method, affecting properties such as swelling power, solubility and gelatinization (Liu et al. 2019). These properties are important because they make the starch more resistant to digestive enzymes and support the growth of beneficial bacterial in the human microbiome. Accordingly, resistant starch can prevent hyperglycemic cycles and reduce the risk of diabetes (Birt et al. 2013; Raigond et al. 2015; Rinaldo 2020), and can improve colonic health and reduce the risk of colon cancer (Sajilata et al. 2006). Hot-air drying at 40 °C has the lowest impact on gelatinization, as well as preserving antioxidant activity and the content of polyphenols and allantoin, so this may be the ideal extraction method (Chen et al. 2017). Resistant starch makes up ~ 50% of the dry tuber weight (Nishimura et al. 2011; Jiang et al. 2012; Chen et al. 2017; Rinaldo 2020) and this may explain the ability of raw Chinese yam starch to lower the serum levels of triglycerides and LDL cholesterol in rodents (Shujun et al. 2008; Nishimura et al. 2011). The health benefits of starch are not only observed in mammals, but also in fish. Chinese yam peel, which is considered a waste product during the processing of tubers, improves the microbiome of the fish gut and can be used as an immunostimulatory feed additive (Meng et al. 2019b). Beyond food and medical applications, yam starch can also be used to create biofilms mixed with antimicrobial ingredients to protect food, such as pork meat and mayonnaise (Cheng et al. 2019a; Oyeyinka et al.2017), or in oxidized form in the paper manufacturing industry (Oyeyinka et al. 2017). These potential applications refer to yam starch in general and thus are applicable to Chinese yam.Other polysaccharidesThe composition of Chinese yam mucilage polysaccharides is unclear, with contrasting studies reporting that they mainly comprise poly(β1-4)mannose with additional linkages and proteins (Ohtani and Murakami 1991), or a mixed composition of mannose, glucose, galactose and glucuronic acid (Ju et al. 2014). Polysaccharides can be extracted in hot water, followed by ethanol precipitation, without losing their functionality (Yang et al. 2015b). Extraction and purification can be challenging because the enzymatic treatment of mucilage polysaccharides to remove proteins also reduces their viscosity and alters other properties (Ma et al. 2018). Polysaccharides extracted from Chinese yam can improve insulin resistance and reduce cholesterol levels, limiting body weight in obese mice probably by inhibiting the uptake of saturated fatty acids (Cheng et al. 2019b). Similarly, anti-diabetic effects were observed in rats fed on diets supplemented with isolated Chinese yam polysaccharides (Fan et al. 2015; Yang et al. 2015a). Such polysaccharides also show antimicrobial activity (Yang et al. 2015c) and the ability to promote the growth of endometrial epithelial cells, suggesting they may help in the treatment of female sterility (Ju et al. 2014). However, this effect may be caused by diosgenin and its derivatives (see below), which are present at low levels in the polysaccharide extracts. Oligosaccharides generated by partial hydrolysis can be used as antioxidant food additives (Chen et al. 2015b). Similarly, low-molecular-weight mucilage extracts with a high content of uronic acid were shown to act as antioxidants with anti-mutagenic activity (Zhang et al. 2016). Seven patents have been granted based on Chinese yam polysaccharides and their derivatives, including a powdered formulation that promotes a healthy gut microbiome (Wang et al. 2019), a herbal medicine with hypoglycemic effects that also reduces the level of blood lipids (Wu 1997), and a mixture of polysaccharides and diosgenin formulated as a cream to facilitate wound healing, reduce skin inflammation and treat vein disorders (Eymard 2005).DiosgeninYams (Dioscorea sp.) synthesize multiple saponins and their aglycone derivatives (sapogenins), many of which show antifungal and cytotoxic effects (Sautour et al. 2007). Diosgenin is a steroidal sapogenin, similar in structure to cholesterol and the human hormones derived from it (Zagoya et al. 1971; Jesus et al. 2016). Diosgenin has therefore been identified as a drug candidate and is used as a precursor for the industrial synthesis of steroid hormones such as cortisone, pregnenolone, and progesterone (Edwards and Duke 2002; Chen et al. 2015a). Chinese yam produces both dioscin (a saponin) and diosgenin (its corresponding sapogenin) although the yield varies greatly in different reports and is likely to be dependent on the cultivar and growth conditions (Edwards and Duke 2002; Yang and Lin 2008; Yi et al. 2014; Wu et al. 2016). However, most of the diosgenin produced by the plant accumulates in the tuber flesh and cortex (Liu et al. 2010). Diosgenin is synthesized from squalene, which originates from the mevalonic acid pathway (Vaidya et al. 2013; Ciura et al. 2017; Hua et al. 2017; Zhu et al. 2018). Diosgenin can also be produced more homogeneously using D. deltoidei cell suspension cultures (Rokem et al. 1985) or genetically modified fungi, the latter also allowing the conversion of diosgenin into other sapogenins (Liu et al. 2010).The functional significance of diosgenin and other steroidal sapogenins in planta has been comprehensively reviewed (Patel et al. 2012; Jesus et al. 2016; Chen et al. 2015a). Pharmacological applications have been claimed in at least 20 patents, describing drug compositions to reduce blood lipid levels (Shan et al. 2014) or diabetic neuropathy (Kim et al. 2014), as well as dermatological applications for the treatment of cellulite (Applezweig 1987) or wrinkles (Besne 2008). Diosgenin is also proposed as a treatment for cardiovascular disease, based on its ability to inhibit cholesterol uptake (Zagoya et al. 1971) and improve the lipid profile (Son et al. 2007) in rodent models. Prebiotic and anti-diabetic benefits also have been proposed because diosgenin can inhibit the activity of α-amylase and α-glucosidase (Huang et al. 2012; Arunrao Yadav et al. 2014). Interestingly, diosgenin has also been indicated for the treatment of Alzheimer’s disease and cancer (Patel et al. 2012; Chen et al. 2015a; Jesus et al. 2016). The former is based on clinical study data in which diosgenin-rich yam extract inhibited neurodegeneration and promoted cognitive stimulation (Tohda et al. 2017). The latter is based on the ability of diosgenin to induce apoptosis in tumor cells (Liu et al. 2005; Meng et al. 2019a) or trigger the corresponding signaling pathways (Raju and Mehta 2009). Finally, the antioxidant effects of diosgenin may reflect its ability to induce the expression and activity of enzymes such as catalase and superoxide dismutase, thus reducing the impact of reactive oxygen species (Son et al. 2007).Chinese yam storage proteins with functional properties – dioscorin and lectinAlthough starch is the principal energy reserve in edible yam tubers, these organs also contain large quantities of storage protein (Shinjiro 1938). The protein content is interesting to the food industry, particularly the segment addressing the growing market for functional vegan foods and beverages (Wu 1998). The major soluble storage protein in Chinese yam tubers is dioscorin, which is a glycosylated form of the enzyme carbonic anhydrase. This means that the protein not only provides nutrition but also confers redox and antioxidant activity. In D. alata, dioscorin gene expression is dependent on meristematic activity during sprouting and tuberization, and is also regulated by environmental stimuli (Liu et al. 2017). Discorin remains stable and soluble following acidic extraction, and also retains its viscosity (Hu et al. 2018). It remains active over a broad pH range, conferring reducing and antioxidant activities presumably via disulfide–thiol exchanges (Hou et al. 1999, 2001; Shewry 2003; Chen et al. 2008; Xue et al. 2012). Despite the beneficial properties of dioscorin, we were unable to find any patents mentioning this protein specifically. Another major protein stored in Chinese yam tubers is a galactose-binding lectin. This is a defense protein that targets insect pests, suggesting it may be transferrable to other crops (Gaidamashvili et al. 2004; Ohizumi et al. 2009; Yoshimura et al. 2012). This protein has also been shown to inhibit cancer cell growth, and may therefore be useful as a lead to develop new cancer drugs (Yang et al. 2011; Chan and Ng 2013).AllantoinAllantoin is major intermediate in the purine degradation pathway and accumulates in plants when uric acid is oxidized (Drewes and van Staden 1975). Allantoin can promote wound healing and cell regeneration, and is often included in skin lotions and other cosmetics (Fu et al. 2006). Yams (Dioscorea sp.) accumulate more allantoin than other tuberous crops, such as potato, sweet potato and cassava (Ozo et al. 1987). Chinese yam tubers contain 2–15 mg/g dry weight of this compound (Fu et al. 2006; Zhang et al. 2014; Liu et al. 2016; Wu et al. 2016) and it is more abundant in the skin than the flesh, making this part of the tuber highly valuable (Fu et al. 2006; Liu et al. 2016). The peel of Chinese yam tubers has greater antitumor activity than the flesh, which may reflect the higher content of allantoin, total phenolics and total flavonoids (Liu et al. 2016). Given that the peel is often discarded during processing, the utilization of this waste stream in a cascade-type approach would add value to the Chinese yam processing industry.Other potentially useful compoundsAs well as the major components described above, other compounds present in smaller amounts may be useful in the context of functional foods and medical applications. For example, phenolic compounds from Chinese yam crude tuber extracts can protect against diabetes by promoting lipid degradation (Zhang et al. 2011; Yang et al. 2013). Specific effects have been attributed to particular phenolic compounds, such as the phenantrenes that accumulate in the peel (Kim et al. 2019). These confer anti-inflammatory, anticholinesterase, and antioxidant properties, as well as inhibiting the accumulation of triglycerides (Tóth et al. 2017). The batatasin family of phytohormones are classed as phenantrenes, and their ability to inhibit α-glucosidase may in part explain the anti-diabetic effects described above (Hu et al. 2015). Another potentially valuable ingredient is the DOI protein, which belongs to the chitinase-like superfamily but shows negligible chitinase enzyme activity (Wong et al. 2015). This protein can stimulate estradiol biosynthesis in rat cells, and is currently being investigated as a protein-based drug for the treatment of menopausal syndrome (Sze et al. 2013; Wong et al. 2015).The future of Chinese yam in Europe and beyondChinese yam has many properties that could help to address today’s challenges in the areas of food security, nutritional diversity, and diet-related health. More than 2 billion people worldwide are classed as obese (Ng et al. 2014), almost 18 million people die each year from obesity-related cardiovascular disease (Wang et al. 2014; Low Wang et al. 2016), and 415 million people suffer from diabetes (~ 90% type 2 diabetes, which is diet related), with the number predicted to exceed 600 million over the next decade (Jaacks et al. 2016). Diet-related health can be addressed using functional foods containing bioactive constituents with multiple health benefits, and this could be achieved by including additives based on Chinese yam extracts (Xiaoqun et al. 2012). Research focusing on yams (and Chinese yam in particular) has been largely overlooked in the past, at least in the West. This could be addressed by international collaborations that combine the traditional knowledge available in China with modern approaches in plant breeding, transformation, genome editing and metabolomics (Price 2017). Chinese yam could be integrated into a new circular bioeconomy, with the tubers and bulbils used to produce nutritional foods as well as pharmaceutical products, and the peel used for the extraction of bioactive compounds and as a functional feed for farm animals and the aquaculture industry.

Author contribution statement

Both authors contributed equally to this work.

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Download referencesAcknowledgementsThe junior research group on Chinese yam cultivation in Europe is funded by the German Federal Ministry of Education and Research (grant number 031B0202). Natalie Laibach is funded within the STRIVE project (Sustainable Trade and Innovation Transfer in the Bioeconomy, www.http://strive-bioecon.de/) by the same ministry (grant number 031 B0019). Many thanks to Richard Twyman for text editing.FundingOpen Access funding enabled and organized by Projekt DEAL.Author informationAuthors and AffiliationsInstitute of Plant Biology and Biotechnology, University of Muenster, Schlossplatz 8, 48143, Muenster, GermanyJanina EppingInstitute for Food and Resource Economics, University of Bonn, Meckenheimer Allee 174, 53115, Bonn, GermanyNatalie LaibachAuthorsJanina EppingView author publicationsYou can also search for this author in

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Reprints and permissionsAbout this articleCite this articleEpping, J., Laibach, N. An underutilized orphan tuber crop—Chinese yam : a review.

Planta 252, 58 (2020). https://doi.org/10.1007/s00425-020-03458-3Download citationReceived: 29 March 2020Accepted: 11 September 2020Published: 21 September 2020DOI: https://doi.org/10.1007/s00425-020-03458-3Share this articleAnyone you share the following link with will be able to read this content:Get shareable linkSorry, a shareable link is not currently available for this article.Copy to clipboard

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The Difference Between Sweet Potatoes and Yams

Sweet Potatoes vs. Yams: Origins, Appearance, and Taste

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Yam - Wikipedia

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From Wikipedia, the free encyclopedia

Look up yam in Wiktionary, the free dictionary.

Yam or YAM may refer to:

Plants/ foods[edit]

Yam (vegetable), common name for members of Dioscorea

Taro, known in Malaysia and Singapore as yam

Sweet potato, specifically its orange-fleshed cultivars, often referred to as yams in North America

Yam, a salad in Thai cuisine

Oxalis tuberosa, referred to as yams in New Zealand and Polynesia

Pachyrhizus erosus, called jícama, Mexican yam bean, or Mexican turnip, a tuberous root

Konjac, Amorphophallus konjac

Geography[edit]

Yam, see Tavastians, old Russian and Ukrainian name for Häme, the tribe of western Finns

Yam fortress, demolished Russian fortress in the modern town of Kingisepp, Russia

Piyam, known also as Yam, a village in Marand County, East Azerbaijan Province, Iran

Yam, Alexandrovsky District, Vladimir Oblast, a village in Vladimir Oblast, Russia

Yam, North Khorasan, a village in Faruj County, North Khorasan Province, Iran

Yam, Razavi Khorasan, a village in Khoshab County, Razavi Khorasan Province, Iran

Yam, Tehran, a village in Pishva County, Tehran Province, Iran

Yam Rural District, in Razavi Khorasan Province, Iran

Yam Island (Queensland), an island in the Torres Strait

Yam-Alin, a mountain range in far North-eastern Russia

Sault Ste. Marie Airport, from its IATA airport code

Names[edit]

Ren (surname), spelled Yam or Yum in Cantonese

Simon Yam, Hong Kong actor

Lindile Yam (born 1960), Chief of the South African Army and lieutenant general

Yam Madar (born 2000), Israeli professional basketball player

Yam, son of Noah, son of Noah in Islamic tradition, who died by drowning in the flood

Yam Kaspers Anshel, Israeli woman who took part in Miss Universe

Other uses[edit]

Yam (god), a Levantine deity not to be confused with Yama, a Hindu God

Yam (route), a former Russian message delivery service introduced by the Mongol Empire

YAM (Yet Another Mailer), a MIME-compliant e-mail client written for AmigaOS based computers

Yellowstone Art Museum

New Yam Festival of the Igbo

Yam languages, a family of Papuan languages

Banu Yam, an Arabian tribe

Yunarmiya (YAM), or Young Army Cadets National Movement, a Russian military youth organisation

Yams: Health Benefits, Nutrients, Serving Suggestions, and More

Skip to main content Home Conditions Back Conditions View All ADD/ADHDAllergiesArthritisAtrial fibrillationBreast CancerCancerCrohn's DiseaseDepressionDiabetesDVTEczemaEye HealthHeart DiseaseHIV & AIDSLung DiseaseLupusMental HealthMultiple SclerosisMigrainePain ManagementPsoriasisPsoriatic ArthritisRheumatoid ArthritisSexual ConditionsSkin ProblemsSleep DisordersUlcerative Colitis View All Drugs & Supplements Back Drugs & SupplementsDrugsSupplementsPill IdentifierInteraction CheckerWell-Being Back Well-Being View All Aging WellBabyBirth ControlChildren's HealthDiet & Weight ManagementFitness & ExerciseFood & RecipesHealthy BeautyMen's HealthParentingPet HealthPregnancySex & RelationshipsTeen HealthWomen's Health View All Symptom CheckerFind a DoctorMore Back MoreNewsBlogsPodcastsWebinarsNewslettersWebMD MagazineBest HospitalsSupport GroupsOrthopedics Privacy & More Subscribe Log In Search Subscribe Diet & Weight ManagementReferenceHealth & Diet GuidePopular Diet PlansHealthy WeightHealthy Eating & Nutrition Vitamins and NutrientsUnderstanding FatsBest & Worst ChoicesTools and Calculators View Full Guide Health Benefits of YamsMedically Reviewed by Zilpah Sheikh, MD on August 30, 2023 Written by WebMD Editorial ContributorWhat Are Yams?Yams vs. Sweet PotatoesTypes of YamsYam BenefitsYam NutritionHow to Prepare Yams4 min read What Are Yams?Yams are tuber vegetables (the type that grows mostly underground) native to Africa and Asia. There are over 600 species of yam, but only 15-20 are edible. Sweet potatoes are often mistaken for yams and may be mislabeled as yams in U.S. grocery stores. It's often hard to find true yams in the U.S. outside of international markets.Yams have a long history of being used in traditional medicine in their native areas.

Purple yams, or ube, are an excellent source of antioxidants. (Photo Credit: iStock / Getty Images)

Yams vs. Sweet PotatoesYams and sweet potatoes are not the same vegetable. Although both grow underground, they come from different plants.Yams are starchier, drier, and less sweet than sweet potatoes. Some varieties of yam can grow up to 130 pounds, in stark contrast to much smaller sweet potatoes. Typically, yams have a tough, scaly skin, while sweet potatoes have smooth skin.True yams have skin that looks something like tree bark. Their flesh can be white, yellow, reddish, or purple.Different varieties of sweet potatoes have white, red, purple, brown, or yellow skin, with flesh that can be yellow, white, or reddish orange. Louisiana and North Carolina produce most of the U.S. supply of sweet potatoes. In grocery stores, sweet potatoes are labeled as either firm or soft. Firm sweet potatoes usually have thin skins and thick flesh and remain firm when cooked. Soft sweet potatoes soften when cooked and are often mislabeled as yams in grocery stores.Types of YamsThere are many varieties of yam, including:African white yams. They are also known as Guinea or Ghana yams. They've been grown in West Africa since 5000 B.C. They're the most commonly eaten yams in Africa.Chinese yams. This species of yam is native to China. This species can grow in more temperate climates than other yams. Unlike other types of yams, Chinese yams are non-toxic when eaten raw.Cushcush yams. Native to the Caribbean, they are popular for their flavor. They're commonly eaten in South America and the West Indies.Purple yams (ube). Also called ube, they are native to Africa and Asia and are most commonly used in Asian cuisine. They grow best in tropical and subtropical regions and are a staple in tropical countries. They contain high levels of antioxidants, substances found in food that fight harmful molecules in your body.‌ Their real nutritional power comes from anthocyanin, pigments that have antioxidant properties.Yam BenefitsYams are rich in vitamins and minerals and are a nutritious food staple in many places outside the U.S. They have many other reported health benefits, though most of the research on this has been on compounds extracted from the yam root. Research is in its early stages. But it has looked at these possible benefits:May prevent and ease arthritis symptomsWild yam root contains diosgenin, which has been shown to limit the progression of both osteoporosis arthritis and rheumatoid arthritis.In one study, mice who were given wild yam extract daily for 90 days showed a drop in inflammation and, at higher doses, pain levels. We need much more research to determine whether it might have these same effects in humans.May reduce cholesterolWhen diosgenin taken from wild yam root was given to mice for 4 weeks, it lowered both their overall cholesterol levels and their LDL (bad) cholesterol levels. Researchers say their results suggest that diosgenin could lower body weight and cholesterol levels. But human studies are still needed.May improve hormone balanceScientists can use the diosgenin in yams to produce estrogen, progesterone, cortisone, and other hormones for medical use. In alternative medicine, yam cream is often used in place of estrogen cream to relieve symptoms of menopause. Women are sometimes advised to eat yams to help balance their hormones, and people with hormone-related conditions are discouraged from using yams medicinally.But studies seem to disprove this usage. The human body doesn't seem to be capable of converting diosgenin into hormones. We need more research, but there's no evidence that using yams to treat menopause, PMS, infertility, and low libido is effective.Yam NutritionNutrients per servingYam nutrition per a 5-inch yam:Calories: 112Fat: 0 gramsCholesterol: 0 gramsSodium: 4 gramsCarbohydrates: 26 gramsFiber: 4 gramsProtein: 2 gramsA single yam packs a whopping 369% of your daily vitamin A requirement. Yam vitamins and minerals also include vitamin C, calcium, and iron.Things to watch out forYams must be peeled and cooked before eating. Many types contain natural toxins that could make you ill.People with hormone-related health issues like endometriosis and uterine fibroids or anyone using estradiol-based birth control or hormone therapy should avoid yam-based medicines or large quantities of yams.How to Prepare YamsWhen shopping, you may see sweet potatoes marketed as yams. To be sure you're buying the right thing, look for a long, tapered shape and a skin that looks more like bark than potato skin.True yams have a very neutral flavor and tough flesh. Like potatoes, they can be baked, boiled, or fried. They also make a nice addition to soups and stews. You can prepare purple yam like you do other yams. Try including cooked purple yams include them in smoothies for color. Ube can also be turned into a powder or paste, which is commonly used to color sweet pastries, cakes, and other baked goods. Sources Update History ShareSOURCES:Biochim Biophys Acta Mol Cell Biol Lipids: "Diosgenin regulates cholesterol metabolism in hypercholesterolemic rats by inhibiting NPC1L1 and enhancing ABCG5 and ABCG8."BMC Complementary Medicine and Therapies: "Bioassay-guided evaluation of Dioscorea villosa – an acute and subchronic toxicity, antinociceptive and anti-inflammatory approach."Endocrine Reviews: "Progestogens Used in Postmenopausal Hormone Therapy: Differences in Their Pharmacological Properties, Intracellular Actions, and Clinical Effects."ESHA Research, Inc., Salem, Oregon.International Journal of Clinical and Experimental Pathology: "Diosgenin inhibits IL-1β-induced expression of inflammatory mediators in human osteoarthritis chondrocytes."Journal of Natural Products: "Diarylheptanoids from Dioscorea villosa (Wild Yam)."U.S. National Library of Medicine: "Wild Yam."University of Massachusetts Amherst: "Sweet Potato."Library of Congress: "What is the difference between sweet potatoes and yams?"Bioscience, Biotechnology, and Biochemistry: "New acylated anthocyanins from purple yam and their antioxidant activity."Food & Function: "The beneficial effects of purple yam (Dioscorea altala L.) resistant starch on hyperlipidemia in high-fat-fed hamsters."Food and nutrition research: "Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits."Planta: "An underutilized orphan tuber crop—Chinese yam : a review."Encyclopedia of Applied Plant Sciences: "Origin and Geographic Distribution."University of Florida: "Cushcush—DIOSCOREA TRIFIDA L."International Journal of Food Science: "Profiling Anthocyanins in Thai Purple Yams (Dioscorea alata L.)," "Roots and Tuber Crops as Functional Foods: A Review on Phytochemical Constituents and Their Potential Health Benefits."Salem Health: "Yam or sweet potato? The surprising difference."How we keep our content up to date:Our medical and editorial staff closely follow the health news cycle, new research, drug approvals, clinical practice guidelines and other developments to ensure our content receives appropriate and timely updates. August 30, 2023Medically Reviewed by: Zilpah Sheikh, MD View privacy policy, copyright and trust info Share View privacy policy, copyright and trust info More on Diet & Weight ManagementIngredients Guide: Facts & Cooking TipsHow to Lose Weight Safely13 Ways to Fight Sugar Cravings Recommended FEATURED Top doctors in , Find more top doctors on Search Related LinksDiet & Weight Management HomeDiet NewsDiet Medical ReferenceDiet BlogsDiet Plans A-ZPopular Diet PlansHealthy Weight GuideHealth Tools & CalculatorsHealthy Eating & NutritionBest & Worst Health ChoicesAll Health Guide TopicsWeight Loss & ObesityFitness & ExerciseFood & RecipesFood CalculatorBMI CalculatorDiabetesCholesterol ManagementMore Related TopicsPoliciesPrivacy PolicyCookie PolicyEditorial PolicyAdvertising PolicyCorrection PolicyTerms of UseAboutContact UsAbout WebMDCareersNewsletterCorporateWebMD Health ServicesSite MapAccessibilityOur AppsWebMD MobileWebMD AppPregnancyBabyAllergyFor AdvertisersAdvertise with UsAdvertising Policy © 2005 - 2024 WebMD LLC, an Internet Brands company. 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