Sweet potatoes (Ipomoea batatas) have been shown to have antioxidant and anti-inflammatory effects. The vegetable is a rich dietary source of vitamin A and vitamin C, and also contains significant levels of vitamin B6, manganese and some copper. Sweet potatoes have a relatively high glycemic index. The high carotenoid and phenolic content of sweet potatoes make them a candidate for possible chemoprevention of cancer, however very few studies have been undertaken to evaluate this potential.
Cancer-related effects of eating sweet potatoes
Purple sweet potatoes (most commonly consumed in Hawaii and parts of Asia), have high levels of anthocyanins, including cyanidin-3-glucoside, which has been shown to possess both chemo preventive and chemotherapeutic activity and to enhance the treatment effects of Herceptin.
Consumption of sweet potato was associated with decreased risk of kidney cancer in one Japanese study and decreased risk of gallbladder cancer in an Indian study. Vitamin A-related components of sweet potatoes have been found to reduce cancerous and precancerous conditions of the uterine cervix. No relevant population studies have been undertaken with respect to sweet potato consumption and breast cancer risk.
The yams sold in U.S. supermarkets are orange-colored sweet potatoes. The true yam is an African and Asian root vegetable belonging to the Dioscoreae family and is only distantly related to sweet potatoes. Sweet potatoes also are not closely related to potatoes (Solanum tuberosum). The intensity of a sweet potato's yellow or orange flesh color is correlated with its carotenoid content and the antioxidant activity of its skin is much higher than the flesh. However, since the exterior may be treated with dye or wax (which cannot be washed off), eat the skin only of organic sweet potatoes.
Wild yam (Dioscorea villosa) or wild Mexican yam, a perennial vine that is used in some women's herbal treatments, is not a variety of sweet potato.
Note that while we are continually searching for new evidence concerning this food, there is not much interest in it among cancer researchers so few recent studies are available.