Rich in vitamin A, potassium and vitamin B6, sweet potatoes are an incredibly nutritious root vegetable. Research has shown that preparation methods profoundly influence the nutrient content of fruits and vegetables. In a comparison of cooking methods, a study published in the 2008 issue of the "Journal of Agricultural and Food Chemistry" found that boiling was generally best for retaining precursors of vitamin A in another root vegetable also rich in the vitamin -- carrots. Frying was the worst.
Boiling Sweet Potatoes for Maximum Nutrient Retention
Wash the sweet potato and lightly scrub the skin with a produce brush to remove any caked-on dirt. Peel the sweet potato, if desired.
Trim the ends of the sweet potato with a kitchen knife to remove the fibrous tips. Slice the root vegetable into similarly-sized chunks to allow the pieces to cook evenly.
Fill a cooking pot with enough water to cover the sweet potato pieces. Select a pot large enough to prevent over-crowding and allows the vegetable pieces room to move in the water.
Boil the sweet potato chunks until they are tender. A knife inserted into the potato's flesh should enter and pull away with little resistance. The pieces should not be so mushy that the potato falls apart when you do this.
Remove the pot from the heat and drain the cooking liquid using a colander.
Mash the boiled sweet potato. Add, if you like, a little cinnamon and nutmeg, place the cubes over a bed of fresh greens in a salad or pair them with black beans in a vegetarian taco.