Ask Tufts Experts

Can you compare the nutritional value of sweet potatoes/yams with white Idaho baking potatoes? What about fiber content? Sweet potatoes seem to contain more fibrous material, but such impressions can be misleading.

Sweet potatoes, yams (technically a different vegetable) and white potatoes all have their nutritional pluses, but you’re correct in thinking that sweet potatoes outdo their white-fleshed cousins in terms of dietary fiber. Exact numbers vary depending on variety, but generally a cup of diced, peeled sweet potato contains 4 grams of fiber—nearly double the 1.8 grams in the same amount of peeled white potato (3 grams if you eat the peel). Yams provide the most fiber of all, with 6.2 grams per cup of peeled, diced yams.

Calorie and protein counts are comparable. As you might guess by their orange color, sweet potatoes contain a whopping amount of vitamin A—almost 19,000 IU per cup, or nearly four times the Daily Value. Yams have only a fraction as much vitamin A—about 200 IU—and regular potatoes, none at all. White potatoes and yams do contain more vitamin C than sweet potatoes, though. Yams provide the most calcium, potassium and folate.