Definition for food

Any substance taken into the body for the purpose of providing nourishment. Factors such as satisfying social needs, achieving psychological ends, and satisfying hunger, more than nutritional needs, govern the selection and consumption of foods. When foods are selected carefully, they can provide all of the essential nutrients needed for normal functioning of the human body. In this context, food is necessary to provide energy, to provide structural components for building and repairing body tissues, and to regulate body processes. There are essential nutrients (carbohydrates, fats, proteins, minerals, vitamins, and water) that have specific functions in the human body. When the energy-yielding nutrients, that is, carbohydrates, fats, and proteins, are oxidized in the body, energy is captured in a chemical compound known as adenosine triphosphate, which will then release the energy slowly so that it can be used for physical activity (work), heat production, and metabolic processes. Enzymes, vitamins, and minerals, as well as water, are needed in order for these oxidation reactions to take place. Energy requirements are expressed in terms of kilocalories (kcal), calories (cal), or kilojoules (kJ). Fats and carbohydrates contain only the elements carbon, oxygen, and hydrogen. Since fats contain less oxygen than carbohydrates, they have greater potential for oxidation and thus provide more energy per gram than carbohydrates. Proteins also contain nitrogen, but this does not contribute substantially to the energy value. The physiological fuel value, or the amount of energy generated in the body, of 1 gram of protein is 4 kcal (17 kJ); carbohydrate, 4 kcal (17 kJ); fat, 9 kcal (38 kJ).