British Food Journal Volume 39 Issue 4 1937

It may be said that the great mass of the food taken by an individual is required and used to satisfy the demands of the body for a source of energy in order that the normal functions and activities of life may be carried out. This energy value of the food was looked upon, until within comparatively recent years, as the important consideration in dietetics. With the accumulation of knowledge regarding the necessity of supplying food essentials, apart altogether from their energy value, this attitude has changed, and it is now known that not only is a certain total quantity of food essential, but that an adequate quantity of the various food essentials must also be supplied. The quantitative problem of dietetics, therefore, resolves itself into a consideration of two aspects which may be considered separately—(1) the total food requirements of the body for energy purposes; and (2) the requirements of the body for the individual food essentials—protein, carbohydrates, fats, mineral salts, vitamins, and water.