How to Cook Sweet Potatoes Without Losing Nutrients

Potato

Sweet potatoes were first cultivated by Native Americans and eventually became a staple of early homesteaders' diets. George Washington was a sweet potato farmer before he became a Revolutionary War general and his soldiers also became fond of them. Eaten raw, a sweet potato does not taste very sweet, but it contains an enzyme that converts the majority of its starches into sugars, causing it to sweeten as it is cooked.

Choosing

Some sweet potato varieties contain more nutrients in the roots and leaves than others, according to the University of Hawaii's Institute of Tropical Agriculture. A good way to choose a sweet potato with high carotene, which your body converts to vitamin A, is to choose one with darker flesh. Once harvested, sweet potatoes' carotene and vitamin C content decreases each day, so buy them fresh and in season to get the maximum amount of nutrients.

Nutrients

A raw medium sweet potato provides 922 micrograms of vitamin A, more than 300 percent of your recommended daily intake of that nutrient, which helps keep your eyes, bones and immune system healthy. It also contains water-soluble vitamins that are at risk of depletion during cooking, including 3.1 milligrams of vitamin C, 0.27 milligrams of vitamin B-6 and 14 micrograms of folate. A sweet potato also provides 4 grams of fiber, 2 grams of protein, no fat and 112 calories.

Steam and Microwave

The water soluble vitamins in a sweet potato diminish rapidly when it is cooked in water. According to Iowa State University's "Journal of Food Science," boiled vegetables may lose up to 1/3 of their vitamin C content, while steaming depletes it by about 1/5. Microwaving and pressure-cooking vegetables help them to retain more than 90 percent of their vitamin C. Researchers from the University of Sydney note that faster cooking methods improve nutrient retention. Food that is kept warm or heated for long periods can lose up to 10 percent more nutrients than food that is cooked quickly. For this reason, microwaving or pressure-cooking your sweet potato are better choices than roasting it.

Boiling

If you must boil a sweet potato, do not peel and cut it up first. Chopping it into small pieces creates a larger surface area, increasing the amount of oxidation and allowing many of a sweet potato's nutrients to boil away. Better to boil the sweet potato whole with the jacket on. After it is finished cooking, let it cool and peel off the skin.

Add Butter

A pat of butter on your sweet potato can be beneficial, according to the North Carolina Sweet Potato Commission. The flesh of sweet potatoes ranges in color from yellow to dark purple to orange. The pigmentation in their skin indicates a the presence of of beta carotene, which your body converts to vitamin A. Because vitamin A is a fat-soluble vitamin, a pat of butter can help your body absorb the sweet potato's vitamin A content, ensuring that you get maximum nutrition.

Cooking Sweet Potato Leaves

According to the University of Hawaii, sweet potato leaves contain only 32 calories per 5/8-cup serving, but provide you with more than 30 percent of your recommended daily intake of vitamin A and small amounts of protein, riboflavin and phosphorus. Cooking these greens depletes some of the nutrients, but if you save the water you cooked them in and use it to make stews or soups, you can get those nutrients back.