Q: What is the difference between a sweet potato and a yam?
A: What are commonly called yams are actually sweet potatoes, which are not really potatoes at all, but storage roots, like carrots. True yams belong to another plant family. You will seldom see a true yam in this country, except in specialty markets. Called njam and grown in Africa and the Caribbean, a yam is pale and starchy, with rough and scaly skin. Canned sweet potatoes are often labeled “yams,” since that’s what most people call them.
There are at least 16 varieties of sweet potato. Skin color ranges from tan to reddish purple, usually with deeply colored flesh.
Sweet potatoes are one of the most nutritious vegetables. A medium sweet potato contains about 10 milligrams of beta carotene (a hefty amount), plus fiber, vitamin C, some B vitamins, vitamin E, magnesium and calcium—even more if you eat the skin. The true yam has no beta carotene and half the vitamin C.
In spite of their sweet taste, sweet potatoes have the same number of calories as white potatoes, about 100 per four-ounce serving. It’s a shame that they often get “candied”— laden with sugar, syrup and marshmallows.