By foods are meant those articles of diet found in the market which contain the chemical elements used by the body in various combinations. Bread, for example, contains all of the foodstuffs and has been called the staff of life, because it sustains life. This refers to bread made from the whole of the grain. White bread, as commonly eaten, is not the “staff of life.” Foods may contain elements, not foodstuffs, and not used by the body, but cast out as waste. Certain foods, such as sugar, corn-starch, olive oil, and egg albumin, contain only one foodstuff, as will be noted in the following classification, in which the foodstuffs are grouped according to the body uses. The classification of foods is based on the principal organic foodstuffs they contain. The preponderance of the elements in any one food determines its chief use in the body. It will be remembered that the chief uses of foods are to produce heat and energy, to build the tissue of the growing child, and to repair the tissues in the child and the adult. Nearly all foods are made up of a combination of substances. The following tabulations give the classification of foods based on their predominating elements. Nitrogenous foods: Lean meat Eggs Gluten Carbonaceous foods: Sugars Starches Root and tuberous vegetables Green vegetables Fruits Fats Carbo-nitrogenous foods: Cereals Legumes Nuts Milk Vegetables are mixtures of sugars and starches; Fruits are mixtures of sugars, vegetable acids, and salts; Milk, legumes, cereals, and nuts contain a more equal division of sugars, fats, and proteins, and are therefore represented as carbo-nitrogenous; Lean meats, with the exception of shellfish, contain no starch, but all meats contain protein, fat, and water. { Water { Corn-Starch { Inorganic { Salts Starches { Sago { { Tapioca { { Carbonaceous { Glucose { (producing { Sugars { Cane Sugar { heat & energy) { { Syrups { { { Honey Foodstuffs { { { { { Lard { Organic { Fats { Olive Oil { { { Butter { { { { { Egg Albumin { Nitrogenous { Proteins { Gluten { (for growth { Lean Meat { and repair) In the above tabulation, examples are given of foodstuffs which are almost pure representatives of their classes. Corn-starch, sago, and tapioca are practically pure starch, containing very little of any other element;