People following a low-carb diet tend to avoid potatoes because they're starchy vegetables, But you may be wondering if sweet potatoes make a better choice, carb-wise, than white potatoes. As it turns out, both have about the same number of carbs per serving. Sweet potatoes are a better source of fiber and vitamins, however, and have a lower glycemic index, so they're a more nutritious choice overall.
Carbs in Potatoes
Potatoes pack a big carb punch, as a 1/2- cup serving of baked sweet or white potato has around 21 grams of carbs. When you count carbs on a low-carb diet, you might be more interested in net carbs, which are the digestible carbs. Net carbs are calculated by subtracting the fiber from the total carb count. Sweet potatoes have 3 grams of fiber per 1/2 cup, and white potatoes have 2 grams, so their net carbs are equal to 18 grams and 19 grams, respectively. Overall, there's not too much of a difference carb-wise, and either potato may be a tough fit if you're following a plan that limits carbs to 20 to 50 grams a day.
About Glycemic Index
In addition to being slightly lower in net carbs, sweet potatoes also have a lower glycemic index, or GI, than white potatoes -- 70 for sweet vs. 82 for white. The GI is a scale that measures how carbs in food affect blood sugar. Foods with a high GI cause a fast increase in blood sugar, while foods with a low GI cause only a small increase in blood sugar over a longer period of time. Maintaining a more even blood sugar helps with hunger control. Even though sweet potatoes have a lower GI than white potatoes, both are considered high-GI foods.
Vitamins and Minerals in White and Sweet Potatoes
Both sweet and white potatoes may be high in carbs and have a high GI, but a sweet potato is the more nutrient-dense choice. A 1/2-cup serving of sweet potato provides more than 300 percent the daily value for vitamin A and 33 percent of the DV for vitamin C. By comparison, the white potato contains no vitamin A and has only 21 percent the daily value for vitamin C. Both vitamin A and C support immune health and act as important antioxidants to protect your body against oxidation from free radicals.
The white potato, however, is a better source of folate, meeting 10 percent of the daily value, while sweet potatoes contain 2 percent of the vitamin. Folate supports red blood cell production and plays a pivotal role in the prevention of neural tube defects such as spina bifida during pregnancy. Both types of potatoes are a good source of the mineral potassium, while sweet potatoes have more manganese than white potatoes.
Serving Potatoes on a Low-Carb Diet
With nearly 20 grams of net carbs per serving, neither sweet nor white potato works on a very-low-carb diet. But if you're consuming up to 50 to 150 grams of net carbs a day, you can fit the high-carb veggie into your diet. Try mixing potatoes with low-carb foods to keep total carbs low. For example, at breakfast sauté a handful of diced sweet potatoes with ham and onions to make a sweet potato hash to go with your scrambled eggs. At lunch, add sliced cooked and cooled white potatoes to your salad greens and toss with vinegar and oil to create your own healthy, low-carb German potato salad. Or roast quartered potatoes with brussels sprouts to serve as a semi-low-carb side dish with your broiled salmon at dinner.