A question that AnswerLine often gets is “what is the difference between yams and sweet potatoes?” And connected to that is “which one is more nutritious? of which should I use?” To begin, what you see in most U.S . supermarkets labeled as yams are really sweet potatoes. So when you thought you were eating a yam, you were really eating a sweet potato; and likely, you have never eaten a true yam. There are two types of sweet potatoes commonly grown and sold in the U.S. One has a pale, yellowish skin and is labeled ‘sweet potato’ and the other has a brownish or brownish-red skin and is usually labeled ‘yam.’ To add to the confusion, canned and frozen sweet potatoes are frequently labeled as ‘yams.’ Despite labeling, either sweet potato variety is nutritionally identical containing the same vitamins, minerals, and calories varying only by growing conditions. They are fat-free, low in calories, high in fiber and great for people who are carbohydrate sensitive. In general, one large baked sweet potato will provide almost three times the vitamin A an adult needs daily and two-thirds the vitamin C requirements. The pale sweet potato is not sweet and after being cooked, the pale variety is dry and crumbly, much like a white baking potato. The darker variety has a vivid orange flesh; it is sweeter, and when cooked, is moist and tender.
A third kind of sweet potato is the flavorful, lavender-fleshed cousin of the familiar orange variety, the purple sweet potato. It is higher in antioxidants than its orange cousin. The purple variety is used in many of the same ways you’d use a regular orange or white potato, and the striking hue adds a colorful twist to mashed potatoes, home fries, and soups. They retain their color best if baked.
Sweet potatoes in general do not store well unless the perfect conditions exist so they should be used quickly. Do not refrigerate. Sweet potatoes can be used in a wide variety of ways.
Yams (true) are a thick, tropical tubers popular in South and Central America, the West Indies, and parts of Asia and Africa. They are related to lilies. Yams are similar to sweet potatoes in size and shape, but yams contain more natural sugar and have a higher moisture content. Yams are an excellent source of potassium, folic acid, zinc, and some B vitamins. They are not as rich in Vitamin C as sweet potatoes and contain no Vitamin A. Depending on the variety, a yam’s flesh may be various shades of off-white, yellow, purple, or pink, and the skin from off-white to dark brown. They may be found in some Asian and Latin markets in the U.S. and are usually sold in chunks by the pound. Like sweet potatoes, they do not store well, should be used quickly, and should not be refrigerated. Yams may be substituted for sweet potatoes in many recipes.