Supplementation with cholecalciferol does not result in weight reduction in overweight and obese subjects.
Investigate whether cholecalciferol supplementation leads to weight loss in overweight and obese adults. Design Randomized double blind clinical trial with 20 000 IU cholecalciferol twice a week, or 20 000 IU once a week plus placebo, or placebo twice a week, for 12 months. All subjects were given 500 mg calcium supplementation.
Conclusion: Significant weight reduction in overweight and obese subjects is unlikely to occur with cholecalciferol supplementation.
http://www.ncbi.nlm.nih.gov/pubmed/19056900
Je ressors une vieille étude qui montre que même lorsqu'on est bien situé et que l'on va beaucoup au soleil, on peut être déficient en vitamine D.
L'étude a été faite à Hawaï sur 93 adultes.
Le temps moyen d'exposition au soleil était de 11,1 heures par semaine.
Résultat: 51% des personnes étaient en déficit.
Low Vitamin D Status Despite Abundant Sun Exposure
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Vitamin D2 or vitamin D3?
http://www.ncbi.nlm.nih.gov/pubmed/18406498
Short and long-term variations in serum calciotropic hormones after a single very large dose of ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) in the elderly.
http://www.ncbi.nlm.nih.gov/pubmed/18492750
The case against ergocalciferol (vitamin D2) as a vitamin supplement.
http://www.ncbi.nlm.nih.gov/pubmed/17023693
Vitamin D2 is much less effective than vitamin D3 in humans.
http://www.ncbi.nlm.nih.gov/pubmed/15531486
"If your levels are below 50 ng/mL you need enough sun, artificial light, oral vitamin D3 supplements, or some combination of the three, to maintain your 25(OH)D levels between 50–80 ng/mL year-round."
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What We Recommend
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Start supplementing with the vitamin D before you have the blood test. Then adjust your dose so your 25(OH)D level is between 50–80 ng/ml, summer and winter. But remember, these are conservative dosage recommendations. Most people who avoid the sun—and virtually all dark-skinned people—will have to increase their dose once they find their blood level is still low, even after two months of the above dosage, especially in the winter. Some people may feel more comfortable ordering the blood test before they start adequate doses of vitamin D. We understand. Test as often as you feel the need to, just remember, no one can get toxic on the doses recommended above and some people will need even more."
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Même lorsqu'on s'expose au soleil, une supplémentation de 10 000IU/j est sans danger:
http://www.ncbi.nlm.nih.gov/pubmed/19364661
Les multivitamines classiques sont incapables de restaurer les taux de vitamine D:
Standard multivitamin supplementation does not improve vitamin D insufficiency after burns.
Supplementation of burned children with a standard multivitamin tablet stated to contain 400 IU of vitamin D(2) failed to correct the vitamin D insufficiency.
http://www.ncbi.nlm.nih.gov/pubmed/19291356
Un déficit en magnésium peut être provoqué par un manque de vitamine D, effet d'autant plus marqué que la personne est en surpoids:
Obesity induced magnesium deficiency can be treated by vitamin D supplementation.
Low serum Magnesium concentration in obese individuals can be modified by vitamin D injection.
http://www.ncbi.nlm.nih.gov/pubmed/19402296
La vitamine D améliore la sensibilité à l'insuline chez les personens en bonne santé présentant une obésité abdominale:
A double-blind, randomized, placebo-controlled trial of the short-term effect of vitamin D3 supplementation on insulin sensitivity in apparently healthy, middle-aged, centrally obese men.
The trial indicates that vitamin D(3) supplementation improves postprandial insulin sensitivity (OGIS) in apparently healthy men likely to have insulin resistance (centrally obese but non-diabetic).
http://www.ncbi.nlm.nih.gov/pubmed/19125756
Encore une nouvelle étude d'intervention randomisée en double aveugle qui montre que la vitamine D augmente la sensibilité à l'insuline mais uniquement si la dose est suffisante:
Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient - a randomised, placebo-controlled trial.
In conclusion, improving vitamin D status in insulin resistant women resulted in improved IR and sensitivity, but no change in insulin secretion. Optimal vitamin D concentrations for reducing IR were shown to be 80-119 nmol/l, providing further evidence for an increase in the recommended adequate levels.
http://www.ncbi.nlm.nih.gov/pubmed/19781131