Vitamin D is a group of fat-soluble chemicals (calciferols). There are two main representatives of this group - ergocalciferol (vitamin D 2 ) and cholecalciferol (vitamin D 3 ). The latter has maximum biological activity, and therefore is the main representative of this group. Moreover, vitamin D 3 can be formed under the influence of ultraviolet rays or come with animal food into the human body, while ergocalciferol comes only with food. However, vitamins D 2 and D 3 are only provitamins for converting them in the liver, and then in the kidneys into an active metabolite - calcitriol, which causes all the effects of vitamin D.
Vitamin D and the sun
An amazing property of vitamin D is its independent formation when exposed to human skin by sunlight and artificial ultraviolet radiation. This happens due to the presence of provitamin in the human epidermis, which, under the influence of solar radiation, turns into vitamin D.
The amount of high-grade vitamin D synthesized from provitamin, among other things, depends on the level of skin pigmentation. It is known that the darker the skin of a person, the less active are the processes of synthesis of vitamin D. This can be regarded as a protective mechanism that does not allow excessive formation of a "solar" vitamin.
However, light-skinned men of the northern countries, deprived of sun exposure, as a rule, do not develop a deficient state of vitamin D, since their diet is rich in seafood, in particular fatty fish, which are a rich source of vitamin D.
The possibility of vitamin D formation under the influence of sunlight weakens with age. This may be one of the reasons that older people are more likely to develop osteoporosis. Against the background of the fact that elderly people do not receive sunlight (spend a lot of time at home), as well as unbalanced nutrition, a vitamin D-deficient state may develop in the autumn-winter period.
Importance in the body and daily requirement
The main properties of vitamin D are in cooperation with calcium in building bone tissue, improving the absorption of calcium and phosphorus in the intestine and their incorporation into bone tissue. As a result, the concentration of calcium in the blood rises, and it more effectively copes with its functions.
In some conditions associated with bone pathology, such as bone fragility, fractures, osteoarticular tuberculosis, osteoporosis, the use of higher doses of vitamin D.
Vitamin D and Testosterone
According to information from Dr. S. Kaadri’s book “Testosterone Factor”, testosterone is involved in building bone tissue, helps to absorb calcium and integrate this element into those parts of the body that it needs.
If calcium intake is insufficient, testosterone molecules are sent to the bones, participating in their restoration. This leads to the fact that less testosterone performs its direct function in the body.
Consuming enough calcium together with vitamin D relieve testosterone from the “maintenance” of the bone, without interfering with its manifesting its hormonal effect elsewhere.
Although vitamin D has an extensive effect on testosterone, the main ones are:
- Collaboration with calcium in bone building (improved absorption of calcium from the intestines and bone mineralization);
- The conversion of estrogen (female hormone) into its less active forms.
The consequences of vitamin D deficiency for men:
- Decreased testosterone effectiveness, with all its consequences.
Sources of Vitamin D
Under ideal conditions, solar radiation is sufficient to meet the daily requirement for vitamin D. It also matters how the effect of sunlight on human skin passes. For example, exposure to sunlight through glass does not lead to activation of cholecalciferol production. The same applies to clothing - on sunny days, you must try to expose to the sun as much as possible areas of the skin (change trousers for shorts, shirts - for T-shirts without sleeves, etc.). Using sunblock also prevents the formation of vitamin A.
Northern residents do not suffer from vitamin D deficiency, as their diet is rich in fatty fish, one of the main food sources of vitamin D. Such fish contain essential omega-3 and omega-6 fatty acids and enough fat for adequate absorption of vitamin D 3 .
Vitamin D is not destroyed by cooking. For the normal absorption of this vitamin, an adequate intake of proteins, vitamins A, C, B vitamins, calcium, phosphorus, and essential fatty acids is necessary. A lot of this combines oily fish.
The content of vitamin D in food:
(estimated availability in 100 g)
Even at the dawn of the discovery of vitamin D, it was shown that irradiation of products with ultraviolet light significantly increases the amount of “solar” vitamin in them. This practice is still popular in the USA, for example, when irradiating milk and other fatty foods.
According to the principle of American food workers, milk rich in vitamin D can be obtained at home by irradiating it with an ultraviolet lamp. With this treatment, 1 liter of milk accounts for the daily need for this vitamin. But only one glass of such milk can be drunk per day!
- V. G. Liflandsky "Vitamins and Minerals", 2010;
- T. P. Emelyanova “Vitamins and Mineral Substances: Complete Encyclopedia”, 2000;
- T. S. Morozkina, A. G. Moiseenok “Vitamins”, 2002;
- Edaplus.info - source of illustrations for the article.