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Vitamin D status and ill health: a systematic review
Prof Philippe Autier MD a b Corresponding AuthorEmail Address, Prof Mathieu Boniol PhD a b, Cécile Pizot MSc a, Prof Patrick Mullie PhD a c
... We did a systematic search of prospective and intervention studies that assessed the effect of 25(OH)D concentrations on non-skeletal health outcomes in individuals aged 18 years or older....
[M]ost prospective [epidemiological] studies reported moderate to strong inverse associations between 25(OH)D concentrations and cardiovascular diseases, serum lipid concentrations, inflammation, glucose metabolism disorders, weight gain, infectious diseases, multiple sclerosis, mood disorders, declining cognitive function, impaired physical functioning, and all-cause mortality. High 25(OH)D concentrations were not associated with a lower risk of cancer, except colorectal cancer.
Results from *intervention* studies did not show an effect of vitamin D supplementation on disease occurrence, including colorectal cancer.
--> In 34 intervention studies including 2805 individuals with mean 25(OH)D concentration *lower* than 50 nmol/L at baseline supplementation with 50 μg per day [ie, [i]2000 IU] or more did not show better results[/i]. [So the standard, otherwise-reasonable complaint that studies are using and/or studying people using too low a dose (eg. 400 IU) doesn't hold water -MR].
Supplementation in elderly people (mainly women) with 20 μg vitamin D per day seemed to slightly reduce all-cause mortality.
The discrepancy between observational and intervention studies suggests that low 25(OH)D is a marker of ill health. Inflammatory processes involved in disease occurrence and clinical course would reduce 25(OH)D, which would explain why low vitamin D status is reported in a wide range of disorders. [For instance, Type II diabetes is driven in large part by inflammatory cytokines spewed out of visceral fat, and atherosclerosis both leads to and is in part driven by inflammation in the injured vessels. Such inflammation would lower 25(OH)D3 levels, which would then lead to these diseases being associated with low vit D levels in epidemiological studies -MR].
In elderly people, restoration of vitamin D deficits due to ageing and lifestyle changes induced by ill health could explain why low-dose supplementation leads to slight gains in survival.
http://dx.doi.org/10...6/S2213-8587(13)70165-7
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