Nutrient: Encyclopedia II - Nutrient - Nutrients and the body

Nutrient - Nutrients and the body

A nutrient is any element or compound necessary for or contributing to an organism's metabolism, growth, or other functioning. Six nutrient groups exist, classifiable as those that provide energy, and as those that otherwise support metabolic processes in the body: Some of them are essential because they cannot be synthesized in the body and must be obtained from a food source.

Substances that provide energy

• Carbohydrates: compounds made up of sugars used or stored as energy. Carbohydrates have three different types of simple sugars, which provide short-term energy that are mostly found in fruits. These are monosaccharide, disaccharide, and polysaccharide. There are also complex carbohydrates, which provide sustained energy, for example, starches and fibers. Complex carbohydrates are stored in the body as glycogen.
• Proteins: nitrogenous organic compounds, including amino acids, that provide the building blocks (amino acids) for enzymes and other proteins within the body. The body does not manufacture certain amino acids (termed essential amino acids): the diet must supply these. Proteins are the most abundant component in the human body. Complete proteins include all nine of the required amino acids in adequate amounts. Incomplete proteins are proteins that lack at least one or two of the essential amino acids.
• Fats: fats can be defined as the basic nutrients composed of carbon and hydrogen atoms and oxygen; they are needed for the proper functions of cells, insulation of body organs against shock, maintenance of body temperature, and needed for healthy skin and hair. including fatty acids (a fat consists of an assemblage of three fatty acids linked to a central glycerine molecule). The body does not manufacture certain fatty acids (termed essential fatty acids): the diet must supply these. Triglycerides make up 95% of our total body fat. The remaining 5% is composed of cholesterol.

Fat has an energy content of 9 kcal/g (~37.7 kJ/g); proteins and carbohydrates 4 kcal/g (~16.7 kJ/g). Ethanol (grain alcohol) has an energy content of 7 kcal/g (~29.3 kJ/g).

Substances that support metabolism

• Minerals: generally trace elements, salts, or ions such as copper and iron; essential to normal metabolism
• Vitamins: organic compounds essential to the body's functions, usually acting as coenzymes
• Water: absolute requirement for normal growth and metabolism directly involved in all the chemical reactions of life — sometimes referred to as the forgotten nutrient.

Any classification of "nutrients" is likely to be arbitrary given the status of nutrition as a developing science. Researchers are becoming more aware of a wider range of nutrients essential for health.

An organism will metabolise any organic compound to use for its energy content, for structural purposes (growth or replacement of living structures), or for participation in chemical reactions necessary for life. Any particular substance can play more than one role in the body, though researchers lack a good understanding of these roles.

The discovery of the group of nutrients called phytonutrients reinforces the provisional nature of our knowledge. We know little about phytonutrients, organic compounds from plants, which play an essential role in the normal functioning of a body and have complex hormonal effects on health, or play an active role in the amelioration of disease. They do not fit readily into the scheme of the traditional nutrition categories.

Adapted from the Wikipedia article "Nutrients and the body", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki