Study leader Ian Reid of the University of Auckland Bone Research Group and colleagues conducted a systematic review and meta-data analysis of studies, and reported in The Lancet that taking vitamin D supplements did not improve bone mineral density in healthy adults with a normal vitamin D level.
"Most healthy adults do not need vitamin D supplements. Our data suggest that the targeting of low-dose vitamin D supplements only to individuals who are likely to be deficient could free up substantial resources that could be better used elsewhere in healthcare," Reid said in a statement. "This systematic review provides very little evidence of an overall benefit of vitamin D supplementation on bone density. Continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems inappropriate."
Analysis of the data from the 23 studies did not identify any effects for people who took vitamin D for an average period of two years, apart from a small but statistically significant increase in bone density -- 0.8 percent -- at the femoral neck.
Such a localized effect is unlikely to be clinically significant, Reid said.
"In North America and Europe particularly, more than half the adult population have their vitamin D level assessed and take vitamin D supplements. Some advocates have suggested that the indicator level for needing vitamin D supplements has been quite high," Reid said. "We believe that vitamin D supplements are only indicated for people with very low levels, such as those who are frail, are confined rest-home residents, or women who are veiled, and some dark skinned people."