The sweet potato is not actually a potato or a yam; it belongs to the Convolvulaceae family- a group of plants that have trumpet-shaped flowers. It commonly has yellow or orange flesh, and its thin skin may either be white, yellow, orange, red or purple.

Sweet potatoes are an excellent source of Vitamin A and Beta-carotene, a good source of Vitamin C, B6, manganese, potassium and fiber. The intensity of the sweet potato's yellow or orange flesh color is directly correlated to its Beta-carotene content. The Beta-carotene in orange-fleshed sweet potatoes is in the form which our bodies can use to produce Vitamin A and is therefore called 'Provitamin A'. Purple-fleshed sweet potatoes are a good source of anthocyanins, which are potent antioxidants that protect the body against degenerative diseases, and they also have the highest antioxidant activity among sweet potato varieties. The red variety of sweet potato is an excellent source of the phytochemical lycopene.

Sweet potatoes contain unique root storage proteins that have been observed to have significant antioxidant capacities. In one study, these proteins had about one-third the antioxidant activity of glutathione-one of the body's most impressive internally produced antioxidants. Furthermore, the antioxidant activity in sweet potato skin, regardless of its color, is almost three times higher than in the rest of the vegetable.

Health Benefits of Sweet Potatoes

Diabetes: One study showed improved insulin resistance when sweet potatoes were included in the diet, and another found that white-fleshed sweet potatoes improved pancreatic cell function, lipid levels and glucose management in animals.

Memory Enhancement: Rats fed purple-fleshed sweet potato showed significant improvement in cognitive function, which may be due to the anthocyanins present in the potato.

Cancer: A cell study showed that sweet potatoes have unique cancer fighting properties.

Breast Cancer: Sweet-potatoes are an excellent source of Beta-carotene, and research found that women who consumed more Beta-carotene foods had lower rates of breast cancer.

Colorectal Cancer: A study found that the development of colon lesions in rats were inhibited when purple sweet potatoes were added to their diet.

Gallbladder Cancer: A study involving diagnosed cases of gallbladder cancer found that sweet potatoes were among the vegetables that offered the greatest protective benefit.

Kidney Cancer: A Japanese study that followed over 100,000 people for about 10 years found that consumption of sweet potatoes was linked to a decreased risk of kidney cancer.

Tips for Using Sweet Potato

• Like potatoes, the flesh of a sweet potato will darken upon contact with the air, so cook it immediately after peeling and/or cutting it. If this is not possible, to prevent oxidation, keep it in a bowl covered with water until you are ready to cook it.

• If selecting sweet potatoes for carotene content, choose darker varieties.

• Sweet potatoes can be eaten in savory dishes cooked in a similar way to potatoes, or enjoyed in sweet pies or puddings, etc.

References

• Philpott, M., Gould, K.S., Lim, C., & Ferguson, L.R. (2004, March). In situ and in vitro antioxidant activity of sweet potato anthocyanins. J Agric Food Chem, 52(6), 1511-1513.

• Hou WC, Chen YC, Chen HJ, et al. Antioxidant activities of trypsin inhibitor, a 33 KDa root storage protein of sweet potato (Ipomoea batatas (L.) Lam cv. Tainong 57). J Agric Food Chem 2001;49(6):2978-81.

• Rabah, I.O., Hou, D.X., Komine, S., & Fujii, M. (2004, November). Potential chemopreventive properties of extract from baked sweet potato (Ipomoea batatas Lam. Cv. Koganesengan.), J Agric Food Chem, 52(23), 7152-7159.

• Kusano S, Abe H. Antidiabetic activity of white skinned sweet potato (Ipomoea batatas L.) in obese Zucker fatty rats. Biol Pharm Bull 2000;23(1):23-6.

• Ludvik B, Waldhausl W, Prager R, Kautzky-Willer A, Pacini G. Mode of action of ipomoea batatas (Caiapo) in type 2 diabetic patients. Metabolism 2003;52(7):875-80.

• Cho J, Kang JS, Long pH, Jing J, Back Y, Chung KS. Antioxidant and memory enhancing effects of purple sweet potato anthocyanin and cordyceps mushroom extract. Arch Pharm Res. 2003 Oct;26(10):821-5.

• Bohle, K., Spiegelman, D., Trichopoulou, A., Katsouyanni, K., & Trichopoulos, D. (1999, January). Vitamins A, C and E and the risk of breast cancer: results from a case-control study in Greece. British Journal of cancer, 79(1), 23-27.

• Hagiwara, A., Yoshino, H., Ichihara, T., Kawabe, M., Tamano, S., Aoki, H., Koda, T., Nakamura, M., Imaida, K., Ito, N., & Shirai, T. (2002, February). Prevention by natural food anthocyanins, purple sweet potato color and red cabbage color, of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP)- associated colorectal carcinogenesis in rats initiated with 1,2-dimethlyhydrazine. J Toxicol Sci, 27(1), 57-68.

• Pandey, M., & Shukla, V.K. (2002, August). Diet and gallbladder cancer: a case-control study. Eur J cancer Prev, 11(4), 365-372.

• Washio, M., Mori, M., Sakauchi, F., Watanabe, Y., Ozasa, K., Hayashi, K., Miki, T., Nakao, M., Mikami, K., Ito, Y., Wakai, K., & Tamakoshi, A. (2005, June). Risk factors for kidney cancer in a Japanese population: findings from the JACC study. J Epidemol. 15(2), 203-211.