In the above table, the skins of the vegetables are included, and while the white potato contains two per cent protein, this is almost all located in a very thin layer immediately beneath the skin, so that when the potato is peeled in the ordinary way, the protein is removed. This holds true in many vegetables. They lose their distinctive flavor, as well as their value as tissue building foods, when the skins are removed. In baking a potato, the outer skin is readily separated from a less perceptible covering containing the protein, and this second skin should be eaten to get the full value and flavor.
In the white potato, of the twenty-two per cent carbohydrates three and two-tenths per cent is sugar and eighteen and eight-tenths per cent is starch. In the sweet potato, ten and two-tenths per cent is sugar and sixteen per cent is starch. Since sugar digests more quickly than starch, the sweet potato digests more quickly than the white. Because of the large per cent or carbohydrates in each, it is a mistake to serve these two vegetables at the same meal. For the same reason, bread and potatoes should not be eaten, to any extent, at the same meal, unless by one who is doing heavy manual labor, requiring much energy.
Onions. Only about four per cent of the onion represents nourishment; the eleven per cent of carbohydrates is made up of two and eight-tenths per cent sugar and the rest extractives. Of the extractives the volatile oil, which causes the eyes to water when peeling, is the most important. The onion is not, therefore, so important for its actual nourishing qualities as for its relish and flavor, and for this it is to be commended. It is a diuretic, encouraging a free action of the kidneys. Because of its diuretic value it is commonly called a healthy food. An onion and lettuce sandwich stimulates the action of the kidneys and is a nerve sedative.
The volatile oil makes the onion difficult for some to digest and, in that case, should be omitted from the diet.
Beets. There is no starch in beets, the seven and three-tenths per cent carbohydrates being sugar; they possess, therefore, more nutritive value than onions, and they are easily digested. It will be noted that it takes many beets to make a pound of sugar.
There are no more delicious nor nutritive greens than the stem and leaf of the beet. These greens contain much iron and are valuable aids in building up the iron in the blood, thus correcting anaemia.
Carrots. Carrots are valuable as food chiefly on account of their sugar. They are somewhat more difficult of digestion than beets and they contain more waste. They make a good side dish, boiled and served with butter or cream.