Vitamins and Supplements

Vitamins perform a catalytic function as part of the active centers of various enzymes, and can also participate in humoral regulation as exogenous prohormones and hormones. Despite the exceptional importance of vitamins in metabolism, they are neither a source of energy for the body (they do not have calories), nor are they structural components of tissues.

With a violation of the intake of vitamins in the body, 3 principal pathological conditions are associated: lack of vitamin - vitamin deficiency, lack of vitamin - hypovitaminosis, excess of vitamin - hypervitaminosis.

Most vitamins are not synthesized in the human body and must be completely absorbed from food. The minority are synthesized in the body: vitamin D, which is formed in human skin under the influence of ultraviolet light; vitamin A, which can be synthesized from precursors that enter the body with food; and one form of vitamin B3 is niacin, the precursor of which is the amino acid tryptophan. In addition, vitamins K and B7 are usually synthesized in sufficient quantities by the symbiotic bacterial microflora of the human colon.

In biological science there is no strict definition of vitamins, there are only the necessary signs for classifying a substance as a vitamin. A substance corresponding to the following four characteristics can be recognized as a vitamin:

organic matter;

a vital substance, without which the clinical picture of the disease develops;

the body does not produce the substance in the required amount or does not produce it at all;

the substance is required in minimum quantities (for a person - less than 0.1 g per day, for example, the highest daily recommended dose for vitamin C, and it is equal to 90 mg).

For 2012, the scientific community recognized 13 substances as vitamins for humans. A few more substances, such as carnitine and inositol, were under consideration, but by 2018 there were also 13 of them in the list of vitamins. However, school textbooks indicate a significantly larger number of vitamins - up to 80, for example, a 2014 textbook says about 20 vitamins.

Based on their solubility, vitamins are divided into fat-soluble - A, D, E, K, and water-soluble - C and B vitamins. Fat-soluble vitamins accumulate in the body, and the place of their accumulation is adipose tissue and liver. Water-soluble vitamins are not stored in significant quantities and, in excess, are excreted in the urine. This explains the greater prevalence of hypovitaminosis of water-soluble vitamins and hypervitaminosis of fat-soluble vitamins.

A wide variety of B vitamins can be found in meat. It also contains small amounts of fat-soluble vitamins. There are more water-soluble vitamins in muscle tissue than in fat, so the relative content of these vitamins will be higher in meat with a lower fat content. So, there is more thiamine in pork, riboflavin in veal.

A person receives daily norms of vitamins with food with an energy consumption of about 3500 kcal per day. Since in the modern world people move little, they do not need so much food, and vitamin supplements become necessary to get the required amount of vitamins. However, in the case of a varied diet, the amount of vitamins in the food is sufficient for a healthy person.