The vitamins are a group of organic substances of different composition, which, in general, animals can not synthesize or make insufficient amount, so it is necessary to ingest the diet because they are synthesized by plants and by bacteria.
Although they are essential for life ("vita"), they are only needed in small quantities. Vitamins are nutrients that, along with other nutritional elements, act as catalysts for all physiological processes, some acting as cofactors for enzymes.
Vitamins are easily altered with changes in temperature, light, or prolonged storage. For example, cooking food cuts the amount of vitamins in half, so it is necessary to eat fresh foods, such as fruits and salads.
Sometimes, the animals cannot take the vitamins directly, but they are in the form of provitamins, which will be transformed to give rise to the vitamins.
The minimum daily requirements of vitamins are not very high, only doses of milligrams or micrograms are needed, but both their deficit and excess can cause problems:
- Avitaminosis: total deficiency of a certain vitamin.
- Hypovitaminosis: partial deficiency of a certain vitamin.
- Hypervitaminosis: excess of a certain vitamin.
The thirteen vitamins can be classified according to their solubility: