From November to March, the UVB intensity is insufficient for the synthesis of vitamin D by the skin. Where fatigue often felt in the heart of winter.
For healthy people, insufficient vitamin D is spoken when the blood concentration falls below 20 nanograms (20 billionths of a gram) per milliliter of blood. “All the experts agree that it’s a decent minimum,” says Professor Jean-Claude Souberbielle, researcher at the Necker Hospital in Paris.
One speaks of deficiency when the concentration falls below 10-12 nanograms per ml. But it is much rarer, affecting mostly the very old people with diseases such as kidney failure.
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A possible link with other diseases!
Vitamin D deficiency also causes muscle weakness, the cause of falls among the elderly. Other conditions associated with it.
In winter, the deficit could be one of the causes of the rise in infectious respiratory diseases.
“Other studies have shown a higher risk of developing dementia, particularly Alzheimer’s disease, in case of failure,” says Dr. Cedric Annweiler, geriatrician.
Vitamin D deficiency has also been linked to the development of cancer (colorectal, breast, pancreas, prostate). It is also associated with an increased risk of hypertension and cardiovascular disease.
But “association” does not mean “causal”. It remains to be confirmed that the lack of vitamin D has a role in the onset of these diseases. It could also be a consequence. And, to date, the studies did not reveal whether supplementation protects against these diseases.
Who should take vitamin D supplements?
After 65 years, supplementation has an interest in preventing falls and non-vertebral fractures, as the femoral neck.
“It is also useful in postmenopausal women with osteoporosis, because treatments work much less well in the event of failure,” said Jean-Claude Souberbielle.
It is also recommended to overweight people with dark skin, those who spend little time outdoors in summer, wearing protective clothes or diet, taking supplements because they often have inadequate or a deficiency, especially in winter.
The vitamin D supplementation is recommended all year round for pregnant women, breastfeeding, young children 2 to 5 years and the elderly living in institutions.
And for the others ? Jean-Claude Souberbielle believes advise the systematic decision without dosage, supplements: “When in doubt, it would be stupid not to correct deficits. Especially as taking vitamin D showed no ill effects. “
Cédric Annweiler, more measured, believes that “it is desirable to supplement systematically populations at very high risk of failure but it is a priori no need to give to those who have no deficiency or deficiencies, since one is not sure of the benefits. “
A not always useful assay for the Health Authority.
The Health Authority considers it, the assay is useful only for a few people: children with suspected rickets, adults with suspected osteomalacia, renal transplant, adults who have had surgery of the obesity and seniors making repeated drops.
For others, it does not recommend the dosage, which is thus no longer paid while it is the only way to know its status in vitamin D.
“We need to save money, says Professor Souberbielle. But we do not know the optimal concentration to reach to help prevent or slow the progression of a disease and it is not known yet whether supplementation provides a benefit, except for musculoskeletal pathologies, of course. Furthermore, without dosing, we come to raise the levels of vitamin D in the margin that is desired, that is to say between 20 and 60 ng / ml. “
Cédric Annweiler nevertheless considers it useful dosage “because the effects of a higher than normal blood levels are still
little known about the long term.”
How to increase vitamin D levels in winter?
If you prefer not to run the risk of lacking vitamin D this winter, three solutions are available to us.
Food: Dairy products fortified with vitamin D, such as yogurt Calin + “By eating two a day is enough to meet the daily intake,” notes Jean-Claude Souberbielle. Oily fish, egg yolk and mushrooms are rich in vitamin D.
Bulbs prescription: GPs can, in turn, prescribe bulbs. Generally, three bulbs 80 000 IU (International Unit) 100 000 IU, with the dosing interval of two to three months.
Finally, dietary supplements containing vitamin D are in free sale in pharmacies.