The vitamin D is a lipophilic Vitamine (soluble in greases) synthesized starting from a derivative of the Cholestérol under the action of the radiations UV of the light. It exists in two forms: D2 ( Ergocalciférol ) or D3 ( Cholécalciférol ).
The vitamin D intervenes in the absorption of the Calcium and of the Phosphore by the intestines, like in their reabsorption by the kidneys, under the influence of PTH Its effects are counterbalanced by the Calcitonine.
A sufficient quantity of vitamin D is particularly necessary during early childhood in order to avoid the Rachitisme, the mother's milk while being relatively poor.
Structure of the Vitamin DTo obtain the structure of the D3 vitamin, add a grouping hydroxyl (- OH) on carbons 1 and 25, thus, you will have of the 1,25 alphadihydroxycholécalciférol, alias D3 vitamin or calcitriol.
The D2 vitamin or Ergocalciférol is a product of irradiation of the ergostérol by the rays Ultraviolet S. The D3 vitamin or Cholécalciférol is the natural vitamin: it is concentrated in oils of Foie like the Poisson. All the Lait S are poor. The vitamin D is formed especially when we expose our body to the sun ( Héliothérapie ). The level of the skin, the ultraviolet rays allow the formation of D3 vitamin normally from derived from the Cholestérol present in the organization. This source is thus very variable according to the exposure to the sun (seasons, fog, area, clothing), the thickness and the pigmentation of the Peau. There is, in theory, never overdose in vitamin D during an exposure to the sun, the latter also intervening in the destruction of this one. In certain situations like an impaired renal function, it is necessary to increase artificially the food supplies of vitamin D. This is done starting from the pharmaceutical preparations which allow a precise proportioning of the contributions of vitamins D (1 Mg of vitamin D = 40.000 units, corresponding, following the marks, either with D2 vitamin, or with D3 vitamin). A person in good health having a varied food and a normal exposure to the sun usually does not need supplement in vitamin D.
A regular exposure to the sun guarantees, at the majority of the people, a good reserve in vitamin D; a Carence in vitamin D can however occur in certain situations in which the vitamin D will be used in preventive Usage.
DepriveIt is defined by a rate of 25-hydroxyvitamine D lower than 50 nmol/l (20 ng/ml). With this limit, the deficiency concerns nearly a billion people on ground and more half of the ménopausées women. This correlation was found only at the people of white Race.
- the blood concentration in vitamin D would be conversely correlated with the prevalence of the arterial Hypertension, the Diabète and the Obésité.
Several arguments, indirect, make think that the vitamin D takes part in the prevention of the Cancer S. On the one hand one observes definitely less colo-rectal cancers in the countries of the South than of North (for the Northern hemisphere), and this, on all the continents. In addition, the administration of D3 vitamin, or cholécalciférols modified, inhibits the induced Cancerogenèse at Rongeur S (more than ten brought back experiments). However, the only clinical trial of great width carried out at volunteers (American) did not show protection. Other studies of less width however seem to contradict the preceding one with a reduction of almost 60% to occurred of cancers crusher-run aggregate among ménopausées women.
Deceleration of ageingThe women who have the most vitamin D in the body would have Télomère S longer than those which miss this vitamin what could have beneficial effects on ageing.
The French health authorities estimate that it is enough to 200 UI of vitamin D per day to be in good health, a level considered to be ridiculous by the international specialists.
Content of vitamin D
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