Vitamins

A vitamin is an organic compound required as a vital nutrient in small amounts by an organism. In other words, an organic chemical compound (or group of related compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from food. Thus, the term is conditional both on the circumstances and the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animals, and biotin and vitamin D are required in the human diet only in certain circumstances. By convention, the term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids (which are needed in larger amounts than vitamins), nor does it include the many other nutrients that promote health but are otherwise required less often. Thirteen vitamins are universally recognized at present.

Vitamins are classified as either water soluble or fat-soluble. Of the 13 vitamins for humans there are four fat-soluble (A, D, E and K) and 9 water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body. Because they are not easily stored for a regular daily intake is important. Bacteria synthesize many types of water-soluble vitamins. Fat-soluble vitamins are absorbed in the intestinal tract, with the help of lipids. Because they are more likely to accumulate in the body, they are more likely to lead to hyper-vitaminosis than are water-soluble vitamins.

Vitamins are essential for the normal growth and development of a multicellular organism. Using the genetic code inherited from its parents, a foetus begins to develop, at the moment of conception, from the nutrients it absorbs. It requires the presence of certain vitamins and minerals at different times. These nutrients facilitate the chemical reactions that produce among other things, skin, bones and muscles. If there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease.

For the most part, vitamins are obtained with food, but a few are obtained by other means. For example, microorganisms in the intestine, commonly known as "gut flora" - produce vitamin K and biotin, while one form of vitamin D is synthesized in the skin with the help of the ultraviolet wavelength of natural sunlight. Humans can produce vitamins from precursors they consume. Examples include vitamin A, produced from beta-carotene, and niacin, from the amino acid tryptophan.

Once growth and development are completed, vitamins remain essential nutrients for maintaining healthy cells, tissues and organs that make up a multicellular organism

Vitamin

Molecule

Role

B1

Thiamine

  • Metabolism of carbohydrates

B2

Riboflavin

  • Metabolism of proteins, lipids and carbohydrates
  • Synthesis of flavins

B3

Nicotinamide

  • Metabolism of lipids, of carbohydrates and of proteins
  • Anti-pellagra

B5

Pantothenic acid

  • Metabolism of lipids, of carbohydrates and of proteins
  • Synthesis of certain hormones

B6

Pyridoxine

  • Metabolism of lipids and of amino acids

B8 (or H)

Biotine

  • Metabolism of fatty acids, carbohydrates and amino acids

B9

Folic acid

  • Synthesis, of purins, pyrimidines, and amino acids

B12

Cyanocobalamin

  • Synthesis of nucleic acid
  • Synthesis of methionine
  • Antianemic (important role in hematopoiesis)

C

Ascorbic acid

  • Synthesis of collagen
  • Synthesis of red blood cells
  • Anti-scorbutic
  • Stimulation of natural defenses and immune
  • Antioxidant

Fat-soluble vitamins

Vitamin

Molecule

Role

A

Retinol

  • Enhances growth
  • Improves vision (anti-xérophtalmique)

D

Calciferol

  • Anti-rickets
  • Enhances the absorption of calcium and phosphorous

E

Tocopherols

Tocotrienols

  • Antioxidant, especially of vitamin A
  • Anti sterility

K1

Phylloquinone

  • Anti hemorrhagic (blood coagulation)
  • Fixes calcium to bones

K2

Menaquinone

English