Although they are nutritionally similar in some ways, sweet potatoes have a lower glycemic index than regular potatoes. As carbohydrates, both types of potatoes are broken down into glucose, which then enters your bloodstream and causes your blood sugar to rise. A low GI means that a food causes a slower increase in blood glucose.
Glycemic Index
The glycemic index is basically a measure of how quickly a food causes your blood sugar to rise. Glucose, the reference food, has a GI of 100. A whole sweet potato has a glycemic index of about 39, while a regular whole white potato ranks about 52, according to "Characterization of the Glycemic Index of Raw and Thermally Processed Sweet Potatoes," a 2007 graduate thesis by Alexis Corbitt of North Carolina State University. In terms of calories and fiber, the two types of potatoes are similar.
How It Works
Your body digests sweet potatoes more slowly than regular potatoes, leading to smaller changes in your blood glucose and insulin levels. This results in a steadier release of energy. Low GI foods also help you stay full for a longer period of time. They are of particular benefit to people with diabetes, coronary heart disease and those trying to lose weight, according to the Glycemic Index Foundation. Such foods also lower the risk of these conditions developing.
GI Ratings
The GI rating of a specific food is determined by the results of feeding test subjects a portion of the food and then measuring their blood sugar periodically for 2 hours. The test data are then compared to reference results obtained from glucose feedings, and the numerical ranking assigned to the food is based on average measurements of the test subjects. Depending on what testing facility is used, the reported glycemic index of a food may vary.
Additional Information
According to a 2011 article by Daneila Hernandez of the "Los Angeles Times," the average American only eats 5.2 lbs. of sweet potatoes annually, compared to 117 lbs. of regular white potatoes. This is unfortunate, since sweet potatoes have much more vitamin A and C than white potatoes. Sweet potatoes have 380 percent of the recommended daily value of vitamin A and 35 percent of vitamin C. White potatoes have only 17 percent the RDA for vitamin C and are not considered a significant source of vitamin A.
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