Roots and tubers constitute a very important class of vegetable foods. They contain both starch and sugar as well as a little pectin and potash salts. They have much less albuminous material than is to be found in any other forms of starchy food, and they also hold a large percentage of water. Many of them are very nutritious and even fattening, but in proportion to their bulk they afford less actual nutriment than either the legumes or cereals.

Sweet Potatoes

The variety known as the sweet potato contains somewhat less starch than the white potato, having but 16 per cent, but it has more water, and a larger proportion of sugar - 10 per cent. It forms a valuable and decidedly nutritious food which is eaten extensively throughout the United States, but it is not so digestible as the white potato, for it cannot always be obtained in a mealy form, and is sometimes stringy and sodden. A flour or meal can be prepared from it by drying. Its use in Europe antedates that of the white potato, which has to a great extent superseded it. These potatoes vary much more in flavour than do the white. In general, they should not be given to invalids.

The yam, another form of tuber, is eaten in the tropics and in some parts of Europe. It is mealy, but not very sweet, and it constitutes a wholesome and thoroughly digestible food.

The Jerusalem artichoke, or ground pear, is a tuber belonging to the sunflower family, which was originally introduced from Brazil. It is used more commonly in England than elsewhere, but is also sometimes cultivated in the United States. It is sweet and watery, for it contains little starch, and it is not "mealy" when cooked. It contains more sugar than the sweet potato, having 14 per cent of sugar, 3 per cent of nitrogenous material, and 2 per cent of inulin (Yeo). Its nutritive value is comparatively slight, but it is easily digested.

The Beet contains among its solid ingredients between 85 and 90 per cent of starches and sugars, a trace of salts, and somewhat over I per cent of proteid matter. It is a common source of sugar, which when refined is sometimes less sweet than cane sugar, but is otherwise as good. On account of the sugar which they contain, beets have the reputation of contributing to the formation of fat in the body. Young, tender beets are very nourishing, and they are often eaten in the form of salads or with vinegar and oil, and thus contribute a useful variety to the diet.