The word foodstuffs (food materials) is a technical term applied to those substances or chemical combinations which are used by animals for food. Starch is a foodstuff. So also are sugar, fat, protein, and certain mineral salts. These substances are, as a rule, taken in combinations. For example, bread is a combination of all of these foodstuffs; perhaps for that reason it has been called the staff of life, because it can support the needs of the material body. Certain foods contain only one foodstuff, as is the case with cane sugar, cornstarch, olive oil, egg albumen.

In classifying food material, we are fortunate in being able to choose a basis of classification which is in harmony not only with the chemistry of these foodstuffs, but also with their use in the body. For example, proteins are used for growth and repair; they are the constructive foods. They differ from all the other foodstuffs in containing nitrogen, sulphur, and phosphates. The nitrogen is so important that the proteins have been called the nitrogenous foodstuffs. The fats, starches, and sugars contain no nitrogen, sulphur, or phosphates, but are especially rich in carbon. They have therefore been called the carbonaceous foodstuffs. The carbonaceous foodstuffs are the energy-producing foodstuffs or the fuels.

Another need of the body is supplied by water and mineral salts, but water and mineral salts are inorganic substances in contradistinction to the nitrogenous and carbonaceous foodstuffs, which are organic substances.