FATS
Fat is a combination of glycerine and certain fatty acids. As a food, it is derived from both the animal and the vegetable kingdom. Animal fat consists of lard, suet, fat meat, etc., while fat of animal origin is represented by cream, butter, and the yolks of eggs. The vegetable fats are found in nuts, especially the pecan, cocoanut, Brazil, and pine nuts; also in the grains, particularly oats and corn. The peanut also contains a considerable amount of fat. Of the fruits, the banana and strawberry contain a trace of fat, while the olive is the only fruit rich in fat.
As a food, fat is used in three forms. The emulsified form is represented by cream, olive oil, and nuts. When the tiny globules of fat, which are each surrounded by a little film of casein, are crushed—united into a solid mass—we have a free fat. This form is represented by butter and other animal fats. Another form is fried fat—fat which has been chemically changed by heat with the development of certain irritating acids.
MINERAL SALTS
The mineral elements comprise but a small part of human food as regards weight, but they are extremely important to the health of the child as well as the adult. As found in the food, they are not in the form of mineral salts, like common table salt. The salts of food are living salts, organic or organized salts, such as are found in the growing plant. These salts are of great value to the various fluids of the body, and also as stimulants to nerve action, but more particularly in the work of building up the bones.
Salts are found largely in the cereals. A small amount is also found in vegetables, particularly the potato, as well as in most fruits.
CELLULOSE
Cellulose represents the great bulk of all vegetables and fruits. It is digested by most animals, but in man it is digested only to the extent of about thirty per cent. The presence of a large amount of cellulose in the food enables us often to satisfy the appetite without injury from overeating. It serves to give bulk to the food, and thereby possibly acts as a preventive to constipation.
WATER
Water fills an important place in the nutrition of the body. The food changes in connection with digestion, assimilation, and elimination, can take place only in the presence of water. Water constitutes from fifteen to ninety-five per cent of the various foods. The watery juices of vegetables and fruits consist largely of pure, distilled water, in which fruit sugar is dissolved, with added flavoring substances. Water is absolutely essential to the performance of every vital function connected with human metabolism.