PROTEINS
The proteins are the structure builders of the body. While starches, fats, and sugars may be compared to the coal that feeds the locomotive, the proteins represent the iron and steel that are used from time to time to repair the engine and replace its worn parts. The essential chemical difference between starch and protein is that the latter contains nitrogen and a small amount of sulphur and phosphorus. The most common forms in which protein is used for food are the glutens of the grains, the legumes, nuts, cheese, the white of egg, and lean meat.