What is Nutrient?
A '''nutrient''' is either a chemical element or [[chemical compound|compound]] used in an organism's [[metabolism]] or [[physiology]]. A nutrient is essential to an organism if it cannot be produced by the organism and must be obtained from a food source.<ref>Sizer F. & Whitney E. 2007. ''Nutrition: concepts and controversies''. Belmont CA: Thompson Wadworth.</ref> This article deals with nutrition in animals, especially humans. Nutrition in [[plants]], [[fungi]], [[bacteria]] and [[archaea]] is not discussed here. == Substances that provide energy == *[[Carbohydrate]]s are compounds made of [[sugar]]s. Carbohydrates are named by the number of sugar units they have. ::[[Monosaccharide]]s (such as [[glucose]] and [[fructose]]) have one. ::[[Disaccharide]]s (such as [[sucrose]] and [[lactose]]) have two. ::[[Oligosaccharide]]s, and [[polysaccharide]]s (such as [[starch]], [[glycogen]], and [[cellulose]]) have more. *[[Protein]]s are [[organic compounds]] that are [[amino acids]] joined by [[peptide bond]]s. The body cannot make some of these; so they must come from food. In the body, proteins are [[catabolism|broken down]] through [[digestion]] back into free amino acids. *[[Fat]]s are a [[glycerin]] molecule with three [[fatty acid]]s attached. Fats are needed to keep [[cell membrane]]s functioning properly, to insulate body organs against shock, to keep body temperature stable, and to maintain healthy skin and hair. The body does not manufacture certain fatty acids and the diet must supply these. These three types of nutrients are often called '''macronutrients'''.<ref>https://www.bhf.org.uk/informationsupport/heart-matters-magazine/nutrition/ask-the-expert/macronutrients</ref> == Substances that support metabolism == *[[Dietary mineral|Mineral]]s are generally trace elements, salts, or ions such as copper and iron. These minerals are essential to human metabolism. *[[Vitamin]]s are organic compounds essential to the body. They usually act as [[coenzyme]]s or [[cofactor]]s for various proteins in the body