Suppression

Yam.

Category: Food

Type

Voluntary

Introduction and description

 

There are actually numerous tubers grown all over the world that are called ‘yams’.  Each has a different medicinal profile, some even come from a different family, thus it seemed more helpful to have this general section on ‘yams’, describe some of the different  varieties and then use the observations to show the differences medicinally.  Thus all the observations for yams are grouped under this heading, but the variety is made clear in the analysis. 

Some varieties of sweet potato (Ipomoea batatas) are also called yam in parts of the United States and Canada, although elsewhere sweet potato is called sweet potato!  Sweet potato has its own entry on the site.

Distribution

Yams are farmed on about 5 million hectares in about 47 countries in tropical and subtropical regions of the world.  Nigeria is the top producer with about 38 million tonnes, followed by Ghana with over 6.5 million tonnes, the Ivory coast with over 5.5 million and Benin, Togo and Cameroon, the Central African Republic and Chad.

In one of the sadder aspects of yam cultivation, economics has entered yam production.  Yams in general have very high medicinal properties, but because Yam production requires high labour,  the crop has low yield per hectare compared to other crops, has a long growing season and is difficult to preserve and store over extended periods of time, economists have been pressurising farmers to grow crops which have nowhere near the medicinal or nutrient value.  One crop they are touting as an alternative is cassava .  Unlike cassava, however, edible, mature, cultivated yams do not contain toxic compounds, which cassava does. Personally, if I was a yam farmer, I would tell the economists to take their alternative crops and stuff them up …...  well you get the idea.

Wikipedia
Despite the high labor requirements and production costs, consumer demand for yam is very high in certain subregions of Africa, making yam cultivation quite profitable to certain farmers.

Too many economists, not enough farmers.

The varieties of yam

Elephant foot yam

 

Amorphophallus paeoniifolius, the elephant foot yam or whitespot giant arum or stink lily, is a tropical tuber.  It is of Southeast Asian origin and grows in its wild form in India, Sri Lanka, the Philippines, Malaysia, Indonesia, and other Southeast Asian countries.  As a crop, it is grown primarily in Africa, South Asia, Southeast Asia and the tropical Pacific islands. In India this species as a crop is grown mostly in Bihar, West Bengal, Kerala, Karnataka, Andhra Pradesh, Maharashtra and Orissa. In the Hindi belt of India it is popularly known as "oal" (ol (ওল) in Bengali, suran or jimikand in Hindi, senai kizhangu in Tamil, suvarna gedde in Kannada, chena (ചേന) in Malayalam, oluo in Oriya, kanda gadda in Telugu and kaene in Tulu.  It is a popular vegetable in various cuisines, and it is the root that is eaten.  The plant gives off a putrid smell. The pistillate (female) and staminate (male) flowers are on the same plant and are crowded in cylindrical masses.

Dioscorea family

 

Yam is the common name for some plant species in the genus Dioscorea (family Dioscoreaceae) that form edible tubers. These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America, the Caribbean and Oceania. There are over 600 varieties of yams and 95 percent of these crops are grown in Africa.  Native to Africa and Asia, yam tubers in this family can vary in size from that of a small potato to over 60 kg (130 lb) and the tubers can grow up to 1.5 meters (4.9 feet) in length.  Some may even grow to weigh up to 70 kilograms (154 lb). The vegetable has a rough skin which is difficult to peel, but which softens after heating. The skins vary in colour from dark brown to light pink. The majority of the vegetable is composed of a much softer substance known as the "meat". This substance ranges in colour from white or yellow to purple or pink in mature yams.

White and Yellow yams


 
Dioscorea cayenensis

Dioscorea rotundata, the "white yam", and Dioscorea cayenensis, the "yellow yam", are native to Africa and are the most important cultivated yams. The White yam's tuber is roughly cylindrical in shape, the skin is smooth and brown and the flesh usually white and firm. Yellow yam is named after its yellow flesh, a colour 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.  Both are large plants; the vines can be as long as 10 to 12 meters (33 to 39 ft). The tubers most often weigh about 2.5 to 5 kg (5.5 to 11.0 lb) each but can weigh as much as 25 kg (55 lb). After 7 to 12 months growth the tubers are harvested.

Winged or Purple yam

 

Dioscorea alata, called "winged yam" and "purple yam", was first cultivated in Southeast Asia. Although not grown in the same quantities as the African yams, it has the largest distribution world-wide of any cultivated yam, being grown in Asia, the Pacific islands, Africa, and the West Indies.  Even in Africa, the popularity of this yam is second only to white yam. The tuber shape is generally cylindrical, but can vary. Tuber flesh is white and watery in texture.  In the Philippines it is known as "ube" and is used as an ingredient in many sweet desserts. In Indonesia it is known as "ubi". In Vietnam, it is called khoai mỡ and is used mainly as an ingredient for soup. In India, it is known as ratalu or violet yam. In Hawaii it is known as uhi. In Japan it is called daijo or beniimo.  Uhi was brought to Hawaii by the early Polynesian settlers and became a major crop in the 19th century when the tubers were sold to visiting ships.

 

Mountain yam

Dioscorea pentaphylla L. is also known as the Mountain Yam or Fiveleaf yam.  It is native to southern and eastern Asia (China, India, Indochina, Indonesia, Philippines, etc.) as well as New Guinea and northern Australia. It is widely cultivated as a food crop and naturalized in Cuba and on several island chains in the Pacific (including Hawaii).  Dioscorea pentaphylla is a prickly vine that may reach 10 meters in length. The alternately arranged leaves are compound, divided into 3 to 5 leaflets each up to 10 centimeters long. The plant produces horseshoe-shaped bulbils about a centimeter long. New plants can sprout from the bulbils. The vine grows from a tuber and specimens may weigh 3 pounds, it is the tuber that is eaten not the bulbils.

Chinese yam

 

Dioscorea opposita, "Chinese yam", is native to China. The Chinese yam plant is somewhat smaller than the African, with the vines about 3 meters (10 feet) long. It is tolerant to frost and can be grown in much cooler conditions than other yams. It is now grown in China, 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. They are eaten as a vegetable, used to make noodles, and used in traditional medicine.

Air Potato, Potato Yam

 

Dioscorea bulbifera, the "air potato", or potato yam is found in both Africa and Asia, with slight differences between those found in each place. It is a large vine, 6 meters (20 ft) or more in length. It produces tubers; however 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 kilograms (1.1 to 4.4 lb).  Some varieties can be eaten raw, while some require soaking or boiling for detoxification before eating. It is not grown much commercially since the flavour 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.  In 1905, the air potato was introduced to Florida and has since become an invasive species in much of the state.

Lesser yam

Dioscorea 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 meters (10 feet) in length and the tubers are fairly small in most varieties.  The tubers are eaten baked, boiled, or fried much like potatoes.

Bitter yam

Dioscorea trifida

Dioscorea dumetorum, the cultivated bitter yam is popular as a vegetable in parts of West Africa; one reason being that their cultivation requires less labour than other yams. Wild forms of bitter yams do contain some toxins that taste bitter. Wild 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.

Cush cush yam

Dioscorea 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 rain forest conditions their growth cycle is less related to seasonal changes than other yams. Because of their relative ease of cultivation and their good flavour they are considered to have a great potential for increased use.

Medicinal uses

Elephant foot yam

The elephant-foot yam is widely used in Indian medicine and is recommended as a remedy in all three of the major Indian medicinal systems: Ayurveda, Siddha and Unani.  The majority of the observations below apply to Elephant Foot Yam, rather than the other types.   The corm is prescribed for bronchitis, asthma, abdominal pain, emesis, dysentery, enlargement of spleen, piles, elephantiasis, diseases due to vitiated blood, and rheumatic swellings. The Ayurvedic Pharmacopoeia of India also indicates the use of corm in prostatic hyperplasia.

Dioscorea family

The USDA Nutrients database does not specify the type of yam, but the following provides some good indicators.  Most roots tend to be high in minerals but not as high in vitamins.  Yam, if we look at the chart below has high mineral and vitamin content and is a very good food.

Yam, raw

Nutritional value per 100 g (3.5 oz)

Energy

494 kJ (118 kcal)

Carbohydrates

27.9 g

Sugars

0.5 g

Dietary fiber

4.1 g

Fat

0.17 g

Protein

1.5 g

Vitamins

Vitamin A equiv.

(1%)  7 μg

Thiamine (B1)

(10%) 0.112 mg

Riboflavin (B2)

(3%) 0.032 mg

Niacin (B3)

(4%) 0.552 mg

Pantothenic acid (B5)

(6%) 0.314 mg

Vitamin B6

(23%) 0.293 mg

Folate (B9)

(6%) 23 μg

Vitamin C

(21%) 17.1 mg

Vitamin E

(2%) 0.35 mg

Vitamin K

(2%) 2.3 μg

Minerals

Calcium

(2%)  17 mg

Iron

(4%) 0.54 mg

Magnesium

(6%) 21 mg

Manganese

(19%) 0.397 mg

Phosphorus

(8%) 55 mg

Potassium

(17%) 816 mg

Zinc

(3%) 0.24 mg

Units

μg = micrograms • mg = milligrams

IU = International units

 Yam, like many other root crops, however, is not a good source of essential amino acids. It is rich in phenylalanine and threonine but limiting in the sulphur amino-acids, cystine and methionine and in tryptophan.

Wikipedia
On the Japanese island of Rishiri, yams and yam products are regarded as a folk remedy for the treatment of impotence, …. likely because of its evocation of virile phallic imagery, according to the common folk medicine theory of sympathetic medicine.

Method

Elephant foot yam

In Bihar Elephant foot yam is used in oal curry, oal bharta or chokha, pickles and chutney. Oal chutney is also called "barabar chutney" as it has mango, ginger and oal in equal quantities, hence the name barabar (meaning "in equal amount").  In West Bengal, these yams are eaten fried or in yam curry. The plant body of elephant foot yam is also eaten in West Bengal as a green vegetable called Bengali: ওল শাক "ol shaak".  In Cambodia, it is known as toal thom (ទាល់ធំ).

Dioscorea family

Yam is an important food 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 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 and good tasty food and a culturally important food security crop in some sub-Saharan African countries.

 

The most common cooking method in Western and Central Africa is by boiling, frying and roasting the yam.  The yam is sliced and peeled and cut into chunks.  Boiled yam may be eaten with palm oil, or a pepper or palaver sauce.  Among the Akan of Ghana, boiled yam is mashed with palm oil and served with eggs.

In the Philippines, the purple ube species of yam (Dioscorea alata), is eaten as a sweetened dessert called "ube halaya", and is also used as an ingredient in another Filipino dessert, halo-halo. In Indonesia, it is mashed and mixed with coconut milk and sugar. It is also used as an ingredient for ice cream. In Vietnam, the same purple yam is used for preparing a special type of soup canh khoai mỡ.

The mountain yam (Dioscorea opposita), is known in Japan as nagaimo or yamaimo (山芋?) and eaten raw and grated. Another variety of yam, Jinenjo, is used in Japan as an ingredient in soba noodles.  Purple yams (Dioscorea alata) are grown in Okinawa and are known locally as daijo (大薯) or beniimo (紅芋). 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 and traditional wagashi sweets, cakes and candy.

In India the yam is boiled, then sautéed and may be sprinkled with turmeric or a few lovage seeds.  The yam is called Soot’hnee and may also be sautéed in butter and dusted with dry mango powder [amchoor].  In central parts of India, the yam is finely sliced, seasoned with spices and deep fried. In southern parts of India, it is known as Karunai Kizhangu (கருணைக்கிழங்கு) in Tamil, and is ‘a popular accompaniment to fish curry’. In the southern part, especially in Kerala, you can see both purple and white coloured yams, locally known as "Kaachil or Kavuttu".

Related observations