Sometimes only the skin is affected, but greening may penetrate the flesh. The green portions contain the alkaloid solanin, which causes a bitter flavor and may have a poisonous effect when consumed in great quantities. Also avoid badly sprouted or shriveled potatoes. Although most commercially marketed potatoes go through a wash process before moving to retail stores, you should wash them again before using, even if you are going to peel them. Nutritive Value Potatoes are an important source of complex carbohydrates.
Potatoes are low in sodium, are virtually fat free, and provide fiber when the skin is eaten.
USDA nutritionists recommend 3 to 5 servings from the vegetable group each day. Go easy on the fat and salt added during cooking or at the table in the form of spreads, sauces, dressings, seasonings, and toppings. The quality of potatoes is judged by external appearance. To help assure quality in the potatoes you buy, the U.S. Department of Agriculture has established grade standards for potatoes. The first U.S. quality standards for potatoes were developed in 1917 to help potato growers and shippers market their product in wholesale channels.