Purpose of review: The 2011 report by the US Institute of Medicine (IOM) on dietary reference intakes for calcium and vitamin D is based on meta-analyses of randomized controlled trials (RCTs), which concluded that vitamin D supplements need to be taken with calcium supplements to prevent falls, fractures, and all-cause mortality. This study reviews recent meta-analyses of RCTs of vitamin D supplementation to determine whether their conclusions are consistent with the meta-analyses underpinning the IOM report.
Recent findings: Since 2007 when the first IOM meta-analysis was published, up to May 2012, there have been nine meta-analyses of RCTs of vitamin D supplements on risk of falls, 10 on fractures, and five on all-cause mortality. About half of these reported summary effects for both vitamin D combined with calcium supplements and also vitamin D alone. However, statistical testing of results from recent meta-analyses does not support the conclusions of the IOM meta-analyses.
Summary: The inconsistency in the conclusions from meta-analyses is due to limitations in the design of previous RCTs of vitamin D supplementation. Large RCTs, giving higher doses of vitamin D (without calcium), should provide a clear answer within several years as to whether vitamin D supplements are beneficial by themselves.
School of Population Health, University of Auckland, Auckland, New Zealand
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