Calcium is needed for building the hard tissues such as the teeth and bones. A diet deficient in calcium is sometimes the cause of poor teeth. Calcium is equally important for body-regulating functions. It is especially necessary that calcium-rich food be given to children.
The most practical and effective way of obtaining calcium is to use a generous supply of milk. Cheese, eggs, and the leaves and stems of plant-foods are also valuable sources of calcium.
Milk, egg yolk, cheese, whole grains, and vegetables are the most satisfactory sources of phosphorus. A free use of these foods is especially desirable since it has been found that phosphorus is quite as necessary as nitrogen. The whole grains are a very valuable source of ash. Many of the ash constituents in cereals are found next to the outer coat of bran, hence fine white flour is not so rich in ash as whole wheat flour.
[Illustration: Foods Containing Phosphorus: a Dried peas; b, chocolate; c, dried beans; d, whole wheat; e, peanuts; f, cheese; g, cocoa; h, egg yolk.]
In the formation of blood and for the welfare of the body as a whole, iron is needed. For this reason, it is often a constituent of "tonics." If foods rich in iron were more generally used, the body would not be so likely to get into a condition requiring such tonics. The iron found in eggs, milk, and vegetable foods is thought to be more completely assimilated than that found in meat. Spinach and prunes are valuable sources of iron. This is one of the reasons why they are most desirable foods for children. The need of eggs, dried fruits, fresh vegetables, and whole grain in diet to furnish iron should be emphasized.
Sulphur is one of the necessary elements of the body. It is usually found, however, as a component of protein; hence if enough protein is supplied to the diet, sulphur will be present in sufficient quantity.
As mentioned, leafy vegetables not only supply calcium but sodium and chlorine,—two of the needed minerals of the body. If fresh vegetables and fruits along with foods rich in calcium, iron, and phosphorus are used, and these foods are cooked and served so as to retain all their nutriment, one can be assured that the diet contains all the necessary ash constituents.
[Illustration: FIGURE 80.—FOODS CONTAINING IRON. a. Dried peas; b. dried figs; c. whole wheat; d. lentils; e. spinach; f. dried dates; g. eggs; h. rye; i. lean beef; j. dried beans; k. raisins; l. dried lima beans.]
C. Food for Regulating.—Although ash is needed for body-building, it also serves to regulate certain body processes as explained previously. Hence if the mineral matter valuable for building is used, the body is also supplied with regulating materials.
D. Food for Promoting Growth.—A discussion of vitamines,—the materials essential for growth of the body and the maintenance of health,—was given in a previous lesson. It is most necessary that foods rich in vitamines be included in diet.