What is the difference between a yam and a sweet potato?

According to the Mayo Clinic dietician, a true yam is a large, starchy root that can get up to 100 pounds. It is native to Africa and Asia and is seldom available in the USA. The sweet potato is a native American plant. It was a staple for early settlers and was actually brought to Europe by Columbus. There are two varieties of sweet potatoes: One is moist and orange-fleshed, the other is drier and yellow. The orange-fleshed potato is commonly - and incorrectly - called a yam. This common practice has resulted in confusion when it comes to labels. Some stores incorrectly label the darker of the two sweet potatoes as being a yam, and they list the nutrient content for yams.

True yams have no vitamin A. So consumers mistakenly think that the product has no vitamin A, even though it actually does. Consumers are most likely eating sweet potatoes - and sweet potatoes are rich in vitamin A, vitamin C and fiber.