Taking vitamin D supplements does not improve bone mineral density, a study involving more than 4,000 healthy adults published in The Lancet has found.
With almost half of adults aged 50 and older in the US using vitamin D supplements, the authors conclude that continuing widespread use of these supplements to prevent osteoporosis in healthy adults is needless.
Professor Ian Reid from the University of Auckland in New Zealand and study leader explains:
"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."
Prof. Reid and colleagues from the University of Auckland conducted a systematic review and meta-analysis of all randomized trials examining the effects of vitamin D supplementation on bone mineral density in healthy adults up to July 2012.
Measuring bone density
Vitamin D supplements are sometimes recommended to those wishing to prevent or treat osteoporosis.
According to the American Academy of Orthapedic Surgeons, osteoporosis affects 10 million people in the US, with a further 18 million at risk of the disease.
Bone mineral density is a measure of bone strength and measures the amount of bone mineral present at different sites.
This measurement was taken at one of five sites - lumbar spine, femoral neck (neck of the femur or thigh bone), total hip, trochanter (part of the femur), total body or forearm. Because the trochanter is a major component of the total hip, the findings for this area were included with the hip.
Analysis of data from 23 studies involving 4,082 healthy adults (with an average age of 59) did not identify any effects for people who took vitamin D for an average period of 2 years, apart from a small but statistically significant increase in bone density (0.8%) at the femoral neck.
According to the authors, such a localized effect is unlikely to be clinically significant.
The authors conclude:
"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 to be inappropriate."
Writing in a linked comment in The Lancet, Clifford J. Rosen from the Maine Medical Research Institute discusses how our recent understanding of vitamin D lends support to these findings.
He points out that for people with normal bones and an adequate calcium intake, there is little or no need for vitamin D supplementation.
"Supplementation to prevent osteoporosis in healthy adults is not warranted. However, maintenance of vitamin D stores in the elderly combined with sufficient dietary calcium intake (800-1200 mg per day) remains an effective approach for prevention of hip fractures."