Does Boiling Potatoes Reduce Their Vitamins?

Cooking any type of food, including potatoes, could lead to vitamin losses. Choosing the proper preparation method for your potatoes can help you minimize these losses so you get the most vitamins from each serving you eat. These vegetables are a healthy carbohydrate source as long as you don't serve them with toppings that are high in fat and calories, such as cheese, sour cream and butter.

Potatoes provide vitamins B-6 and C, thiamine and niacin. Niacin is heat-stable and not usually lost in significant amounts due to cooking, but at least some of the thiamine and vitamins B-6 and C may be lost when potatoes are boiled. The amount of vitamins lost depends on how you prepare the potatoes before boiling.

Boiling potatoes whole in their skins minimizes the amount of vitamin C that is lost. According to the Food and Agriculture Organization of the United Nations, boiling unpeeled potatoes results in losses of up to 30 percent of vitamin C, but boiling peeled potatoes can cause losses of up to 40 percent. About 2 percent of the vitamin B-6 is lost due to boiling potatoes, as well as about 23 percent of the thiamine. A 3.5-ounce serving of potato boiled in the skin provides 22 percent of the daily value for vitamin C, but boiled peeled potatoes provide only 12 percent. Peeling potatoes before boiling can also increase vitamin B-6 losses, with unpeeled boiled potatoes containing 15 percent of the DV per 3.5-ounce serving and peeled boiled potatoes containing only 13 percent of the DV. There is no difference in thiamine content between peeled and unpeeled boiled potatoes.

Vitamin C and the B vitamins are water-soluble, which means that if you soak your potatoes in water or boil them, some of the vitamins may leach out into the water. Vitamins B-6 and C and thiamine are also heat-sensitive, so the higher the temperature and the longer the cooking time, the more of the vitamins will be lost.

Steaming and microwaving both minimize contact with water, making them good choices for cooking potatoes. Washing the potatoes just before cutting them, cutting them into large pieces instead of small pieces and cooking them right away after cutting them can also help minimize vitamin losses. A study published in the "Journal of Hygiene Research" in July 2007 found that braising helped retain thiamine, riboflavin and vitamins B-6 and C more than boiling.