A nutrient is either a chemical element or 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.
Substances that provide energy
- Carbohydrates are compounds made up of sugars. Carbohydrates are classified by their number of sugar units: monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).
- Proteins are organic compounds that consists of the amino acids joined by peptide bonds. The body cannot manufacture some of these; therefore the diet must supply these. In nutrition, proteins are broken down through digestion back into free amino acids.
- Fats consist of a glycerin molecule with three fatty acids attached. Fatty acids are unbranched hydrocarbon chains, connected by single bonds alone (saturated fatty acids) or by both double and single bonds (unsaturated fatty acids). Fats are needed to keep cell membranes 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.
Substances that support metabolism
- Minerals are generally trace elements, salts, or ions such as copper and iron. These minerals are essential to human metabolism.
- Vitamins are organic compounds essential to the body. They usually act as coenzymes or cofactors for various proteins in the body.
- Water is an essential nutrient and is the solvent in which all the chemical reactions of life take place.
The following table gives an idea of what elements are essential for humans:
Periodic table highlighting dietary elements
|The four organic basic elements||Quantity elements||Essential trace elements||Possible structural or functional role in mammals|
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