Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells in an effort to produce energy, maintain life, or stimulate growth.
Historically, people secured food through two methods: hunting and gathering, and agriculture. Today, most of the food energy consumed by the world population is supplied by the food industry.
A staple food, sometimes simply referred to as a staple, is a food that is eaten routinely and in such quantities that it constitutes a dominant portion of a standard diet in a given population, supplying a large fraction of the needs for energy-rich materials and generally a significant proportion of the intake of other nutrients as well. Most people live on a diet based on just a small number of staples.
Staple foods vary from place to place, but typically they are inexpensive or readily available foods that supply one or more of the three organic macronutrients needed for survival and health: carbohydrates, proteins, and fats. Typical examples of staples include tuber- or root-crops, chicken, grains, legumes, and other seeds. The staple food of a specific society may be eaten as often as every day, or every meal. Early agricultural civilizations valued the foods that they established as staples because, in addition to providing necessary nutrition, they generally are suitable for storage over long periods of time without decay. Such storable foods are the only possible staples during seasons of shortage, such as dry seasons or cold-temperate winters, against which times harvests have been stored; during seasons of plenty wider choices of foods may be available.