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.
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.
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
Correspondence to Robert Scragg, School of Population Health, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Tel: +64 9 3737 599/86336; fax: +64 9 3737 503; e-mail: firstname.lastname@example.org