The four great classes a re: (a) Nitrogenous foods or flesh-formers, so called because they either build up
new body tissues, or repair bodily waste, (b) Hydrocarbons or fats which help to maintain bodily heat and
produce energy, (c) Carbohydrates or starchy foods which also help to maintain the heat of them body as
well as to form fat. (d) Minerals, including water and salt, are essential for the repair and growth of all parts
of the body.