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Sunday, 12 October 2014

What is vitamin D ? How much do we need to be healthy?

Vitamin D

Vitamin D or vitamin antirachitic calciferol or a vitamin is liposoluble ie soluble in fats. Its uniqueness lies in the fact that its main source is made ​​by the body itself.
There are several variations of vitamin D but the forms that interest us the most are:
- vitamin D2 or ergocalciferol , which is of plant origin . It is found in most foods.
- vitamin D3 or cholecalciferol , which is synthesized in the skin by the action of ultraviolet on cholesterol. Vitamin D3 is also present in animal foods such as fish oils.


Background of Vitamin D

- 1865 : physician Armand Trousseau recommends in its manual of clinical medicine the cod liver oil consumption because it has a antirachitic factor. Trousseau is also one of the first, after Russian Sniadecki, observing that exposure to sun protect children rickets.
- 1890 : English physician Palm, after an epidemiological study concluded that the only common denominator to explain the Rickets is a lack of exposure to sunlight.
- 1922 : McCollum discovers that cod liver oil retains its properties even antirachitic after destroying every vitamin A. There is therefore a second soluble factor which he called "vitamin dépositrice calcium. "
- 1924 : Dr. Harry Steenbock and Dr. Hess show that ultraviolet radiation can induce antirachitic factor in food and animals.
- End of the 20s : it is clear that rickets can be prevented and cured by exposure to direct sunlight, ultraviolet radiation, for consumption of irradiated food or cod liver oil.
- 1932 : the crystalline vitamin D2 were isolated pure.
- 1936 : crystals are pure vitamin D3 isolated from liver oil tuna.
- 1952 : Dr. Woodward made ​​the first synhtèse Vitamin D3 which earned him the Nobel Prize in Chemistry in 1965.
- 1964 : Norman detects the existence of three metabolites of vitamin D. In 1971, he established the structure of calcitriol.
- Since 1980 , receptor derivatives of vitamin D were found in the cells of many organs.

The role of vitamin D

Vitamin D plays two key roles. Firstly, it ensures optimal bone mineralization, during growth, but also throughout the life of their renewal.

Moreover, it modulates intestinal calcium absorption contributes to the stability and rate of calcium in the blood and tissues.
But that's not the only benefit of vitamin D for the body. Indeed, this vitamin is the subject of many experiments since the 90s, some researchers have high hopes on it to prevent many diseases.

Cancers 
It seems to be a link between vitamin D levels and the development of cancers. Indeed, some studies point to a greater risk of being hit by one of these diseases when vitamin D levels in the body are too low. In addition, people who already have potentially have a greater chance of survival with higher levels of vitamin D.

Depression
The link between lack of vitamin D and depression is still unclear to researchers but they generally consider this vitamin as a neurosteroid and agree on the likely importance in the brain. Vitamin D may, for example, facilitate the production of noradrenaline, dopamine and serotonin. Deficiency could thus lead to depressive disorders in those affected.

Cognitive disorders
As with depression, vitamin D deficiency may increase the risk of developing Parkinson's disease. Indeed, this vitamin has a protective effect on neurons and prevent that they be destroyed.

Falls and Fractures
The problem is especially common among the elderly. The bones become brittle and fractures are more common. However, vitamin D supplementation could reduce the risk of fractures due to the effect of this vitamin on the binding of calcium. But it is also true for falls because the elderly with vitamin D levels too low, were also more likely to fall. This is due to loss of balance and muscle weakness possibly caused by a lack of vitamin D.

The vitamin D in the body

- Vitamin D from the diet is absorbed with fats in the small intestine. It then joins the general circulation.
- Vitamin D formed by irradiation of the skin pass directly into the bloodstream.
- Vitamin D is mainly stored in the blood, muscle, adipose tissue, liver, kidney .
- It can then be dispatched to the intestines, bones, kidneys, muscles, the parathyroid glands .
- Vitamin D and its derivatives are eliminated by the fecal bile .

Physical and chemical properties

- heat-sensitive
- sensitive to light
- sensitive to O2
- sensitive to acid

Vitamin D needs

The needs are difficult to evaluate because they vary with the degree of sun exposure and the degree of skin pigmentation . They are theoretically zero if the body exposure to sunlight is sufficient.

A vitamin D is necessary in countries where sunlight is weak, especially in children during the first two or three years of life.

Sources

Most of the vitamin D is synthesized in the skin due to exposure to sunlight . One sees that with a minimum of exposure (15 to 30 minutes a day) the bulk of the vitamin D - 50 90% -. Skin is produced by the rest of the vitamin D is provided by the feed , primarily by fish oils, fish, butter, cereals, eggs, livers of animals and also a little milk.

Functions

Vitamin D has a key role in calcium metabolism : - it facilitates the intestinal absorption of calcium and phosphorus - it helps the binding of calcium to the bones ie their growth, but also for their renewal its renal excretion . - it acts as a hormone and hypercalcémiante will enter into relations with other hormones on calcium and phosphate metabolism.


Vitamin D deficiency

- In adults, vitamin D deficiency may result in osteomalacia (demineralization with osteopathy ostéoïdose by hypophosphocalcie)
- In children and adolescents, the rickets (due to defective bone mineralization of growing organism ostéochondrodystrophie fast and usually secondary to vitamin D2)
- Other consequences of vitamin D deficiency: osteoporosis , increased infections

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