These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America, the Caribbean and Oceania. There are many cultivars of yam. Although some varieties of sweet potato (Ipomoea batatas) are also called yam in parts of the United States and Canada, sweet potato is not part of the family Dioscoreaceae but belongs in the unrelated morning glory family Convolvulaceae. Yam is a good source of energy; 100 g provides 118 calories. Its crunchy edible tuber chiefly composed of complex carbohydrates and soluble dietary fiber. Dietary fiber help reduce constipation, decrease bad (LDL) cholesterol levels by binding to it in the intestines and lower colon cancer risk by preventing toxic compounds in the food from adhering to the colon mucosa. Additionally, being a good source of complex carbohydrate, it regulates steady rise in blood sugar levels. For the same reason, yam recommended as low glycemic index healthy food. The tuber is an excellent source of B-complex group of vitamins. It provides adequate daily requirements of pyridoxine (vitamin B6), thiamin (vitamin B1), riboflavin, folates, pantothenic acid and niacin. These vitamins mediate various metabolic functions in the body. Fresh root also contains good amounts of anti-oxidant vitamin; vitamin-C. Provides about 29% of recommended levels per 100 g. Vitamin C play some important roles as anti-aging, immune function booster, wound healing, and bone growth. Yam contains small amounts of vitamin-A, and beta-carotene levels. Carotenes convert into vitamin A inside the body. Both these compounds are strong antioxidants. Vitamin A has many functions like maintaining healthy mucus membranes and skin, night vision, growth and protection from lung and oral cavity cancers. Further, the tuber indeed is one of the good sources of minerals such as copper, calcium, potassium, iron, manganese, and phosphorus. 100 g provides about 816 mg of Potassium. Potassium is an important component of cell and body fluids which helps controlling heart rate and blood pressure by countering hypertensive effects of sodium. Copper is required in the production of red blood cells. Manganese is used by the body as a co-factor for the antioxidant enzyme, superoxide dismutase. Iron is required for red blood cell formation.