Vitamin D is important at various stages of life: why, where it is found, how much of it is needed, how and when to supplement it
What is the vitamin D, how it is produced, what it is used for, when it is necessary to integrate it.
1. What is Vitamin D
It is actually more than just a vitamin: it is a real hormone, that is, a substance capable of stimulating various functions of the organism. In recent years it has emerged that it controls directly or indirectly the regulation of the activity of beyond 1250 genes.
2. Where does it come from
Like all hormones, vitamin D can be produced “internally” by the body. However, there is no particular gland dedicated to this purpose, as happens for the other hormones: in this case the skin functions as a gland, where the synthesis of vitamin D occurs following exposure to sunlight.
Vitamin D is also naturally present in some foods, but the amount of this vitamin that we can get in our diet is limited
3. How Much Vitamin D Matters for Bones
Its role in bone metabolism has long been known. In particular: it promotes bone mineralization by modulating the absorption of calcium and phosphates in the intestine. This is why it is essential for bone growth during childhood and adolescence – but also earlier, that is, during the fetal life – and for the remodeling of the bone, normally subjected to continuous processes of destruction and reconstruction, during adult life.
Vitamin D deficiency
- bone fragility,
Vitamin D deficiencies in children they can lead to bone fragility or, in severe cases, a rickets. Even in adults, the deficiency of this substance leads to bone fragility. Along with that of calcium, an adequate intake of vitamin D is essential to protect against the risk of osteoporosis. But be careful: it is very important that the contribution is adequate from childhood: it is more difficult to run for cover in adulthood, if there were deficiencies as children.
4. What is vitamin D used for, in addition to bones
In recent years, it has emerged that vitamin D performs many other functions besides those related to the skeleton. For example it is very important for muscle activity, is also involved in the modulation of cell growth, in immune functions and in the attenuation of inflammatory mechanisms.
5. How vitamin D is produced
The starting point for the synthesis of vitamin D in the skin is a substance derived from cholesterol, which thanks to the action of type B ultraviolet rays is in fact converted into vitamin D (or rather, vitamin D3) or cholecalciferol. In this form the hormone is not yet fully active: it becomes so after a series of chemical steps that occur in the liver, where the so-called cholecalcifediol is produced. [25 idrossivitamina D o 25(OH)D] and at the kidney level, where the most active form of all is produced, the calcitriol.
For the sake of accuracy, there is also another form of vitamin D, la vitamin D2, of vegetable origin.
6. What happens if exposure to sunlight is low
Since it is UVB rays that stimulate the synthesis of vitamin D, if exposure to sunlight is poor there is a reduced production of hormone, risk of shortage of vitamin D.
Warning: Various factors contribute to modulating the actual level of exposure to sunlight. Between these:
- latitude (trivially, in Sicily the actual hours of sunshine available during the year are higher than in Paris …);
- cloud cover;
- the level of atmospheric pollution;
- skin complexion (dark skin absorbs less UV rays);
- the use of sun filters.
7. What happens if exposure to sunlight is excessive
Taking too much sun does not involve particular problems with respect to the production of vitamin D. Its synthesis, in fact, is subjected to self-regulation mechanisms which, in case of excess UVB rays, lead to the production of inactive molecules.
However, remember that troppo Sole is bad for the skin for other reasons (risk of skin aging and development of skin cancers).
How Much Sun for an Effective Vitamin D Synthesis?
A recent document from the US National Institutes of Health Food Supplements Office points out that some researchers believe they are needed 5 to 30 minutes of sun exposure of the face, arms and legs (or back) at least twice a week to obtain an adequate synthesis of vitamin D. It is better to use the sun in the late morning or early afternoon, however, corresponding to the time slot in which dermatologists advise against taking it to avoid risk of skin damage. Probably for these conflicting needs there are currently no official guidelines on the subject.
8. How much vitamin D is needed
According to the latest indications of the …