Extension connection: Of sweet potatoes and yams

Published 12:00 am Thursday, November 29, 2007

By Angela Treadaway / Guest Columnist

I receive a number of online newsletters on food topics, all of which I carefully screen to verify the writers are Registered Dietitians or Food Scientists. Recently, I was intrigued by a discussion of the nutritional and appearance characteristics of sweet potatoes and yams. I realize that only a food scientist could be intrigued by such a topic, but nevertheless, I was. I thought you might be interested in what I learned.

A reader in cyberspace had asked Dr. Irene’s Nutrition Tidbits (www.healthandage.com) to clarify distinctions of the two vegetables. The reader had commented that food stores display white or yellow sweet potatoes and that the yams alongside them are orange. They then asked which is more nutritious?

Sweet potato data, as expected, shows outstanding nutritional value. They are an excellent source of fiber and Vitamin C but are best known for their richness in Vitamin A. Vitamin A is critical in vision, growth, cell health and bone remodeling. In the sweet potato, Vitamin A is primarily in the form of beta-carotene, which our bodies modify into Vitamin A. We are capable of storing up to two years’ supply in our livers, and, if the source of Vitamin A is food, not supplements, there is no risk of toxicity.

Sweet potatoes are also a fair source of Vitamin B-6 (pyridoxine), folic acid and several other essential nutrients. Essential nutrients are those that our human bodies cannot make for ourselves. While sweet potatoes are a good source of these nutrients, they are low in a couple we get too much of such as fat and sodium. Sweet potatoes are a nutritional bargain for the 160 calories in a small baked sweet potato (about 1/2 cup).

References on yams, on the other hand, show they do not contain any Vitamin A. They have roughly the same nutritional value as Irish potatoes — which isn’t at all bad. But how can they lack Vitamin A, since their color is often deeper than sweet potatoes? The answer is that what you are buying in the United States is not a yam, but a different variety of sweet potato.

Some years back Louisiana farmers started calling their sweet potatoes yams to differentiate them from varieties of sweet potatoes grown further north. True yams are never orange or sweet. They are an African and/or Asian crop, which has a rough, dark outer skin and pale insides. They are considered staples in many parts of the world and you will usually find them in the ethnic section of a supermarket. Sweet potatoes, on the other hand, appear to have originated in Mexico and Central and South America.

Whether you plan to have yams or sweet potatoes for the holidays, it probably will be a sweet potato, an excellent and delicious addition to your diet.

PotA’to? PoTAH’to? Either way, sweet potatoes are loaded with vitamin A and are a good source of fiber.

Angela Treadaway is a regional extension agent serving Shelby County. She can be reached by phone at 410-3696