Yams are a type of dry, starchy root vegetable, or "tuber," similar to the potato. Like many root vegetables, yams have a high carbohydrate count -- between 22 and 42 grams per serving, depending on yam type. In general, yams have more carbohydrates per serving than either red, white, russet or sweet potatoes.
Standard Yam Nutrition Info
According to the USDA Agricultural Research Service, one serving of a regular yam contains nearly 42 grams of carbohydrates. One serving is defined as about one cup of cubed yam. This also includes 6.2 grams of dietary fiber, 177 calories and 2.3 grams of protein. Yams are very low in fat -- less than half a gram per serving -- and low in sugar with less than one gram per serving.
Mountain Yam Nutrition Info
A type of Hawaiian yam known as mountain yam is lower in calories, carbohydrates and fiber than standard yams. A one-cup serving of mountain yam yields 22 grams carbohydrate, 91 calories and 3.4 grams fiber. Mountain yams are similarly low in sugar and fat to regular yams, with under one-half gram of each per cup. Mountain yams have about half the magnesium and phosphorous content of regular yams, and less than half the potassium content.
Other root vegetables look low in carbohydrate content compared to yams. One cup of diced Russet potatoes contains just 27 grams carbohydrate, and one cup of white potatoes contains 23.5 grams, about the same amount of carbohydrates as can be found in a serving of red potatoes. Sweet potatoes -- which many people in the United States consider interchangeable with yams, though they're different vegetables -- are also lower in carbohydrates, with about 27 grams of carbohydrates per serving.
Because of the high carbohydrate content in yams, people on low- or zero-carb diets may want to avoid this vegetable. Sweet potatoes, Russet potatoes, white potatoes and red potatoes are all less carbohydrate-heavy root vegetable choices. For the carb-conscious who want to eat yams, Hawaiian ''mountain yams'' are an alternative. One serving of mountain yams contains about 20 grams less carbohydrate than a serving of regular yams.