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Vitamin D deficiency consequence of poor health, not cause
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Vitamin D deficiency is not the cause but a consequence of poor health, according to findings from a systematic review.
These data raise questions as to what the protective value of vitamin D supplementation is, according to Philippe Autier, MD, MPH, of the International Prevention Research Institute in Lyon, France, and colleagues.
“If the health benefits of high vitamin D concentrations shown by data from observational studies are not reproduced in randomized trials … then the relation between vitamin D status and disorders are probably the result of confounding or physiological events involved in these disorders,” Autier said in a press release.
The researchers used data from 290 prospective observational studies (279 on disease occurrence and 11 on cancer characteristics or survival) and 172 randomized trials to examine the effect of vitamin D on outcomes other than bone-related health up to December 2012, according to data.
Prospective study data indicate increasing 25-hydroxyvitamin D is associated with moderate to strong decreases in cardiovascular disease, serum lipid concentrations, serum markers of inflammation, glucose metabolism disorders, weight gain, infectious diseases, mood disorders, declining cognitive function and impaired physical functioning, researchers wrote.
Although prospective studies did not suggest a protective effect of 25-(OH)D on cancer except for colorectal cancer, the benefits from high vitamin D concentrations were not confirmed in randomized trials.
The meta-analyses and pooled analyses also demonstrated that vitamin D supplementation could significantly reduce the risk for all-cause mortality with RRs ranging from 0.93 to 0.96, according to researchers.
“What this discrepancy suggests is that decreases in vitamin D levels are a marker of deteriorating health. Aging and inflammatory processes involved in disease occurrence and clinical course reduce vitamin D concentrations, which would explain why vitamin D deficiency is reported in a wide range of disorders,” Autier said.
In an accompanying editorial, contributors from TheLancet: Diabetes & Endocrinology wrote that despite the growing body of evidence demonstrating that vitamin D is unlikely to prevent non-skeletal disorders, there also is strong support for its use from various research entities.
“Large clinical trials to assess the effects of vitamin D on non-skeletal health outcomes are therefore justified. It would be a real boon to patients if the results are positive, but unless effect sizes for clinically important outcomes are large, the results will only confirm the neutral effect reported by most clinical trials thus far,” they wrote.
Disclosure: The researchers report no relevant financial disclosures.
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