Food componentsThe three major components of food, known as macronutrients, are proteins, fats, and carbohydrates.
Proteins are chemical chains of various combinations of 20 naturally-occurring amino acids. Muscle tissue consists mainly of proteins. The body breaks up dietary proteins into amino acids that are used for tissue repair, to produce many of the hormones and enzymes that regulate metabolism, and as a source of energy. The chemical processes of the body require nine of these "essential" amino acids in the diet. Other amino acids may be synthesized from these nine. Unlike animal proteins, plant proteins may not contain all the essential amino acids in the necessary proportions for good health. Vegetarian diets must contain the right balance of grains and legumes to prevent dietary deficiency diseases.
Each point of unsaturation, indicated by a double bond between carbons, can have a Cis or a Trans configuration which affects the shape of the molecule and its biochemical properties. A saturated fat does not have double bonds and cannot accept any additional hydrogen atoms. In general, unsaturated fats are liquid and saturated fats are solid. Most vegetable oils have a higher proportion of unsaturated to saturated fats than animal fats. Some unsaturated fats, called "essential fatty acids" (EFA), are necessary for the development and maintenance of the brain and eyes. Hydrogenation is a commercial chemical process to add more hydrogen to natural unsaturated fats to make them solid. Partial hydrogenation has the side-effect of transforming a portion of the natural Cis fatty acids to Trans fatty acids which can have harmful health effects.
Non-digestible components such as fiber and cellulose are not nutrients, but they create bulk that helps to clean the intestines and moderate the absorption of nutrients. A portion of the ingested fiber is fermented by microflora in the intestines and converted into short-chain fatty acids that can be metabolized. Refined foods have a lower content of fiber than whole foods. White wheat flour, for example, has less fiber than whole wheat flour because the outer shell of the wheat grains is discarded in making the white flour.