Food is any material eaten to supply the body with nutrition. When people talk about food, they generally mean both diet and food eaten in daily life. Generally, food is of plant, animal, or fungi origin, and is generally of nutritional quality, including proteins, vitamins, fat, carbohydrates, or minerals. In recent years, however, the term food has become more narrow in definition, referring not only to dietary products but also to man-made materials used for food processing. The major categories of food are foods manufactured for consumption and food supplies used in agricultural production. In addition, food can refer to any living thing that feeds or requires nourishment.
Plants produce food plants, which include all the plants used for food, as well as the plants themselves and the food they grow. Animals produce food animals, which include cattle, poultry, fish, rabbits, swine, deer, and wild animals, as well as milk products derived from farm animals. Fungi produce food fungi, which include all types of fungi used in food production. Animal foods such as meat, milk, eggs, fish, feathers, fur, nails, organs, and bones are animal foods. Human foods produced by living people include all the food consumed by individuals, whether they live in communities of mankind or have a small degree of separation. Foods produced by inorganic natural systems, including fossil fuels, mined minerals, nuclear waste, chemicals, and biodegradable wastes, are called organic foods. Plants produce food through respiration, absorption, and excretion, although some types of photosynthesis do not need food at all.
A food system is a complex network of interactions among living things to ensure the proper functioning of all the systems. Among these systems are metabolism, nutrient absorption and excretion, nutrient transport, nutrient storage and utilization, pest control, and signal transduction. All living things must be connected in a food chain to achieve optimal health and wellness. This food chain is highly organized because it is controlled by the natural processes of living things, unlike the highly structured metabolic process, which is controlled by biochemists and other scientists.