According to a new study, healthy adults do not need to take vitamin D supplements.
The study published in The Lancet found the subjects had no beneficial effect on bone density, a sign of osteoporosis.
Experts say many other factors could be at play and people should not stop taking supplements.
University of Auckland researchers analyzed 23 studies involving more than 4,000 healthy people.
The New Zealand research team conducted a meta-analysis of all randomized trials examining the effects of vitamin D supplementation on bone mineral density in healthy adults up to July 2012.
The supplements were taken for an average of two years by the study participants.
Bone mineral density is a measure of bone strength and measures the amount of bone mineral present at different sites in the body. It is often seen as an indicator for the risk of osteoporosis, which can lead to an increased risk of fracture.
The trials took place in a number of different countries including the UK, the US, Australia, Holland, Finland and Norway.
Although the results did not identify any benefits for people who took vitamin D, they did find a small but statistically significant increase in bone density at the neck of the femur near the hip joint.
According to the authors, this effect is unlikely to be clinically significant.
Prof. Ian Reid, lead study author, from the University of Auckland, said the findings showed that healthy adults did not need to take 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.”
Writing about the study in The Lancet, Clifford J. Rosen from the Maine Medical Research Institute agrees that science’s understanding of vitamin D supports the findings for healthy adults, but not for everyone.
“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 remains an effective approach for prevention of hip fractures.”
The Department of Health currently recommends that a daily supplement of vitamin D of 10 micrograms (0.01 mg) should be taken by pregnant and breastfeeding women and people over 65, while babies aged six months to five years should take vitamin drops containing 7 to 8.5 micrograms (0.007-0.0085 mg) per day.