Source  : Health Canada. Canadian Nutrient File , 2010.

The benefits of yam

There are hundreds of varieties of yams , but only a few are edible ¹ . Whole yam, as eaten, has received little research, despite the few medicinal properties attributed to it. In addition, the majority of studies have been done on animals. More studies will need to be done on humans to find out if the different results can apply to them.

• Blood lipids . A study in women showed that the daily consumption of almost 400 g of yam (about 5 servings), for 30 days, decreased total blood cholesterol, but had no effect on LDL and HDL cholesterol. ⁷ . Researchers believe that the fibers , sterols or the combined action of these yam compounds would decrease the absorption of fat in the intestine.

  In animals, a study has shown that by replacing part of the food starch with raw yam, it reduces total cholesterol and LDL cholesterol (“bad” cholesterol), but also HDL cholesterol or “good »Cholesterol (the latter effect being undesirable)¹⁰ . According to another study, adding a compound found in yam, diosgenin, to the animal diet, would have benefits on blood lipids (cholesterol and triglycerides ¹⁵ ) and would also reduce oxidative stress ^{14 , 15} .

• Blood pressure . A protein extracted from yam has been shown to reduce blood pressure in vitro ¹¹ . In hypertensive rats, yam consumption, both in liquid than in powder form, also reduce blood pressure ¹⁷ .
• Cognitive impairment . In animals, ingestion of yams would have beneficial effects on cognitive disorders. Thanks to its antioxidant properties, yam acts on the brains of mice and improves their skills related to learning and memory ²¹ .
• Diabetes . A study in rats has shown that the consumption of yam powder during meals contributes to better control of glucose and insulin concentrations ²⁰ .
• Protection of the liver and kidneys . A study has shown that a raw yam extract, added to the rodent diet, helps protect the liver and kidneys from damage caused by high doses of acetaminophen ¹² or alcohol ¹³ . Another study indicated that the yam powder, administered to rats, it possible to protect the liver against the fibrosis liver ¹⁸ (a disease characterized by the formation of fibrous plaques to the liver may lead to cirrhosis or insufficiency hepatic). However, other studies have shown that yam extracts can induce renal or hepatic fibrosis in animals ¹⁹ .
• Menopause symptoms . Traditionally, yams are used to treat certain symptoms of menopause. Despite successful trials in animals ^{5 , 6} , in humans, taking yam supplements has not confirmed this effect (see our Wild yam (psn) ) ^7-9 . The consumption of yams cannot therefore be recommended to reduce hot flashes or other symptoms of menopause ¹⁶ .

What does yam contain?

Although it is primarily considered a source of carbohydrates (sugars), this vegetable contains several important vitamins and minerals , as well as proteins.

Antioxidants
Yam has antioxidant properties ^{2 , 3} which are partly attributed to the phenolic compounds it contains. These would be more abundant in raw yam than in boiled or fried yam ²³ . The antioxidant capacity of the yam differs according to each variety ²² . Dioscorin ⁴ is one of the most abundant proteins in yam and also the most studied for its antioxidant potential. In addition, it could play an important role in the hypotensive effect of a yam extract by inhibiting an enzyme which participates in the regulation of blood pressure.arterial ¹¹ .

Diosgenin
In light of the data obtained in animals, the cholesterol – lowering effect of yam is partly due to the presence of diosgenin. This compound would also participate in the estrogenic action observed in animals ^{5 , 6} . On the other hand, according to the researchers, the estrogenic compounds of yam are not sufficiently active in the body ⁸ and only a consumption of very large quantities of raw yam could bring about estrogenic activity ⁹ . In addition, it seems that the estrogenic activity of yams differs from one plant to another and according to the variety ⁹ .

Main vitamins and minerals

To access other recipes, you can go to the CuisineAZ.com cooking recipe site, which offers, among others, the following recipes : yam-based recipes , yam gratin, yam puree

The yam is a large floury tuber, rich in starch. Like the sweet potato, it lends itself to the same culinary uses as the potato. Clearly sweeter than the potato, its flesh also makes it possible to make desserts , marmalades , pudding , cookies , cakes , ice cream , pancakes and other desserts .

The yam has a tough bark, which is difficult to peel, but which tenderizes when cooked. The flesh is tender, white or yellow, pink if the vegetable is very ripe.

• In thick slices grilled on the barbecue or browned in the pan. Cook until the inside is tender. Season with fresh herb.

• In soups or velvety .
• Use the tubers in the couscous .
• Cook them in water and serve them with a good homemade sausage and lentils.
• Patties . Grate the tubers and finely chop an onion. Press in a cloth to extract the juice, mix with eggs and flour and fry in a pan. If desired, season the preparation with cumin, hot peppers and curry.
• In a soup , with chicken broth, crème fraîche, lime fillet and ginger.
• Cook the cubed yams with onion and squash pieces in coconut milk seasoned with cloves, cinnamon and salt.
• Prepare them in brandade of fish .
• In Cuba , yams are seasoned with a marinade of hot olive oil, lemon juice, raw onions cut into thin slices, garlic, cumin and a little water.
• The best way to prepare the small aerial tubers of Chinese yam (see section Organic gardening ) is to brown them in a pan in a little oil, turning them until they are just right.

The term ”  yam  ” comes either from Inhame Portuguese or Iname Spanish , both derived from an African language.

The genus Dioscorea comprises many species, of which the main 4 are cultivated in tropical regions of the world. Two of these species come from Southeast Asia, two others from Africa. There is a known 5 ^th  species, native to South America, which has never been economically important because of competition from sweet potato, potato and cassava, all from the continent.

Archaeological excavations in southeast Asia suggest that yam was already consumed in this region 12,000 years ago. It was probably a wild species. Its domestication dates back at least 4,500 years before our era, perhaps even before. Little information is available on the origin of African yams, but they could have been domesticated on this continent 6000 years before our era. These species will be introduced in the tropical regions of South America at the end of the XVI ^E  century with the boats transporting the slaves.

Today, the yam, like the sweet potato, is cultivated in all tropical countries, where it constitutes an important food resource . Farm animals are also fed in several places.

In temperate regions, yam is difficult to grow because it requires a long frost-free season. However, the Chinese yam ( Dioscorea batatas or D. opposita ), which should not be confused with the wild Chinese yam ( D. villosa ) (see our file Wild Yam (psn) ) with medicinal properties, s adapts relatively well to our climates. Perennial in zone 5, this splendid climbing plant requires a support, for example a wooden trellis, of at least 2 m to 3 m, and good sunshine. We can also cultivate it with beans. It is spread by small aerial tubers harvested in the fall and kept in the cellar all winter to plant in the spring.

To get ahead of the season, you can plant the aerial tubers in pots that will be kept indoors, in a warm layer or in a greenhouse until thawed.

The soil must be loosened to encourage the growth of tubers. They can have respectable dimensions, without however exceeding the meter long they reach in hot countries.

The pH is indifferent.

Apply a phosphate and potassium-based fertilizer , without straining the nitrogen.
Make sure that irrigation is constant, but avoid that the plants have their feet in the water.
Harvest the aerial tubers in September and the terrestrial tubers in October.