Sweet potatoes are often called yams, yet the two belong to different botanical classifications. Although called a potato, sweet potatoes do not belong in the same group as white potatoes, such as the russet potato; they belong to the morning glory family. While one cup of cooked sweet potato in the skin provides only 180 calories with virtually no fat, no cholesterol and very little sodium, sweet potatoes and their skin serve as a good source of fiber and provide many nutrients.
Beta Carotene
Beta carotene belongs to the group of carotenoids, fat-soluble pigments, found in a variety of fruits and vegetables. Beta carotene functions as an antioxidant, meaning that it protects cells from the damaging effects of free radicals–negatively charged atoms produced by chemical reactions involving oxygen. In the body beta carotene, a provitamin, transforms into vitamin A. Sweet potato skins serve as one of the best sources of beta carotene, providing four times the recommended daily intake, according to the North Carolina Sweet Potato Commission.
Fiber
The US Department of Agriculture 2005 Dietary Guidelines for Americans recommends adults intake 14g of dietary fiber, the portion of a plant-based food the digestive system cannot break down, per 1,000 calories consumed. This represents significantly more fiber than the average adult gets each day, which the Colorado State University Extension reports as 14g per day. Eating sweet potatoes with the skin on can help you reach your daily fiber intake goals. One medium sweet potato contains 4g of dietary fiber, according to information provided by the Produce for a Better Health Foundation. As with many fruits and vegetables, the skin contains the majority of the fiber. Eating a high-fiber diet promotes a healthy digestive system and can help lower cholesterol levels, therefore decreasing the risk of heart disease.
Complex Carbohydrates
Sweet potatoes provide energy to your body in the form of complex carbohydrates, which consist of three or more sugars linked together. Because the body takes longer to break down and utilize complex carbohydrates, eating complex carbohydrates does not produce a dramatic spike in blood sugar and therefore helps to prevent the onset of type II diabetes. Foods that contain fiber generally provide more complex carbohydrates since the body takes longer to break down the fiber. One whole medium sweet potato contains 23g of carbohydrates, according to the Produce for a Better Health Foundation.
Vitamin E
In addition to functioning as an antioxidant, vitamin E also supports a healthy immune system and helps maintain normal signaling between cells. The National Institute of Medicine Food and Nutrition Board recommends adults intake 15mg of vitamin E per day. Although many of the natural sources of vitamin E contain significant amounts of fat, such as nuts, seeds and vegetable oil, two-thirds of a cup of sweet potatoes provides 100 percent of the recommended daily intake without any added fat.
【Reference】
http://www.livestrong.com/article/355542-sweet-potato-skins-and-nutrition/
