Large Review Casts Cloud Over Vitamin-D Health Benefits
Further Insights Will Emerge From Ongoing Trials The researchers note that important further insights should emerge from 5 trials that are currently under way. These trials involve between 2150 and 20,000 patients aged 50 years or older and are investigating the effects of 40 to 80 µg/day of vitamin-D supplementation on the risk of cancer, cardiovascular disease, diabetes, infections, declining
cognitive function, and fractures.
"The first results are not expected before 2017, but these studies have the potential to test our hypotheses," theyobserve.
In an accompanying comment, the editors say the key factors that drive continued research into vitamin D for the prevention of nonskeletal disorders include "the relatively low toxicity of vitamin D, the glimmer of positivity from some trials, and the large body of evidence from prospective observational studies."
Dr. Autier agreed, adding that commercial influences, such as the vitamin-D supplement industry and manufacturers of vitamin-D testing products, have also helped fuel the enthusiasm. "Commercial influences were more than happy about the explosion of observational data on vitamin D and diseases,"
he told Medscape Medical News. "A third main player is the artificial UV tanning industry, which encourages tanning
booths because of the 'vitamin-D sufficiency' issue."
Vitamin-D Supplementation "Ill-Advised"
For proponents of nonskeletal health benefits from vitamin D, there is no shortage of potential explanations for the lack of results in interventional studies, the editors add.
"For those who 'believe,' the lack of benefit found in most trials completed thus far can be attributed to issues including inadequate supplementation, testing of a population not sufficiently vitamin-D deficient at baseline, incorrect formulation, underpowering, or insufficient follow-up," they observe.
Dr. Autier noted that trials conducted prior to about 2000, such as the large Women's Health Initiative, did indeed use low doses or involved too few subjects to reach a sound conclusion, but he added, "More recently published randomized trials have taken care of these aspects, and these arguments are less relevant than, say, 5 years ago." Some supplementation if an individual's vitamin-D concentration falls below a "sufficiency" threshold of 75 nmol/L continues to be recommended — an ill-advised practice, Dr. Autier asserted.
"The wealth of evidence from randomized trials shows that this medical behavior is not grounded and taking vitamin-D supplements will make no difference on health status," he said. "It would be wiser to seek reasons underlying the low vitamin-D level, such as inflammatory processes or undiagnosed cardiovascular diseases, and fix them." The authors have reported no relevant financial relationships.
Lancet Diab Endocrinol. Published online December 6, 2013. Abstract and Editors' Comment
Medscape Medical News © 2013 WebMD, LLC
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Cite this article: Large Review Casts Cloud Over Vitamin-D Health Benefits. Medscape. Dec 06,2013
- Dr. Noble Zachariah M.D.
Specialist- Internal Medicine and Diabetes,
International Clinic, Farwaniya
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