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Classification of Foods

All foods are divided into two classes: the nitrogenous, or those which contain nitrogen, and the non-nitrogenous, or those that do not contain nitrogen. The nitrogenous are divided into two classes, the albuminoids or proteids, and the gelatinoids. The principal proteids are found in eggs, fish, meat, casein of milk, fiber of lean meat and the gluten of wheat. The white of an egg is almost entirely albumen. In the body these go to the formation and repair of tissue waste, the regulation of absorption and the utilization of oxygen. They may form fat, and they are partially converted into peptones in digestion.

The second division, or gelatinoids, are found in the collegan, or the gelatin of cartilage, and the ossein, or the gelatin of bones. These have the same function in the body as the proteids, but less perfectly. It is this form of food which gives the jelly-like consistency to our soup stocks.

The non-nitrogenous foods are divided into three classes: the carbohydrates, the hydrocarbons and the vegetable acids.

The carbohydrates consist of starch, dextrine, cellulose, cane sugar, maltose, lactose, dextrose and levulose. All of these supply heat and energy by oxidation, or burning; supply fat by reducing the burning of the proteids, and are converted into dextrose during digestion. Digestion begins in the mouth, where the starch is changed to a form of sugar by the action of the ptyalin of the saliva.

The final condition of all starch in digestion is dextrose. The hydrocarbons consist of fats and oils. The fats are composed of three fatty acids: olein, the fatty acid of lard; stearin, or the fatty acid of suet; palmitin, or the fatty acid of butter. All of these supply heat and energy by burning or oxidation, and they also supply fatty tissue. The oils are known as fixed or volatile. The fixed oils are those that leave a stain, as olive oil, and the volatile oils are those which evaporate, as the essences. These oils have the same functions as the fats.

The third division, or vegetable acids, are found in the fruits; oxalic, or the acid of rhubarb; tartaric, or the acid from grapes; citric, found in lemons; malic, found in tomatoes; acetic, found in vinegar, and lactic, found in sour milk.

All of these preserve the alkalinity of the blood.

The minerals consist of the salts, chlorides, phosphates, etc, and these have various uses. Water is nature's great solvent and carrier of food and waste products.