Of the carbohydrates, next in importance to the sugars and to the starches in their purest form (cornstarch, tapioca, sago, and arrowroot), come the roots and tubers, such as potatoes, sweet potatoes, beets, parsnips, turnips, and onions. The following table shows the proportion of various foodstuffs in these vegetables. The skins of the vegetables are included. TABLE I ROOTS AND TUBERS ——————————————+—————————+—————————+—————————+—————————+—————+—————————— | Water | Protein | Fat |Carbo- | Ash |Food Value FOOD MATERIALS|per cent.|per cent.|per cent. hydrates |per |per pound | | | |per cent.|cent.| Calories ——————————————+—————————+—————————+—————————+—————————+—————+—————————— Sweet Potatoes| 69.4 | 1.5 | 0.3 | 26.2 | 2.6 | 440 White Potatoes| 75.0 | 2.1 | 0.2 | 22.0 | 0.7 | 295 Parsnips | 64.4 | 1.3 | 0.4 | 10.8 | 1.1 | 230 Onions | 86.0 | 1.9 | 0.1 | 11.3 | 0.7 | 225 Beets | 87.0 | 1.4 | 0.1 | 7.3 | 0.7 | 160 Carrots | 88.2 | 1.1 | 0.4 | 8.2 | 6.0 | 210 Turnips | 92.7 | 0.9 | 0.1 | 0.1 | 0.6 | 120 ——————————————+—————————+—————————+—————————+—————————+—————+—————————— _Potatoes._ It will be noted from the table given above that sweet potatoes contain a larger percentage of carbohydrates, hence they produce more heat and energy than any other vegetable; next to the sweet potato comes the Irish or white potato. While the white potato contains two per cent. of 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 is true of many vegetables. They lose their distinctive flavor, as well as their value as tissue-building foods, when the skins are removed, especially before cooking. Many vegetables may be peeled after being cooked and their value in nutrition is thus increased. All tubers gain in dietetic value if they are cooked in their skins, the thin outer covering being removed after the cooking process is completed. The ordinary cook, however, is unwilling to take the trouble to prepare them in this way. In vegetables as usually prepared for the table the proportion of carbohydrates is increased and the proportion of protein is diminished. The skins render many of the foods unsightly, hence they are discarded in the preparation for cooking. When a potato is baked the outer skin is readily separated from the less perceptible layer containing the protein. Potatoes boiled in their skins retain the protein. In the white potato, of the twenty-two per cent. of 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.