Intake of vitamin D supplements may not prevent fractures or falls, or improve bone mineral density in adults, a large-scale study claims.
The meta-analysis of 81 randomised trials, published in The Lancet Diabetes & Endocrinology journal, also found no differences in the effects of higher versus lower doses of vitamin D.
Researchers from the University of Auckland in New Zealand conclude that there is little justification to use vitamin D supplements to maintain or improve musculoskeletal health.
The exception is for the prevention of rare conditions such as rickets and osteomalacia in high risk groups, which can occur due to vitamin D deficiency after a prolonged lack of exposure to sunshine, they said.
Vitamin D supplements have long been recommended for older people to treat or prevent osteoporosis, with some early evidence suggesting benefits for bone health.
However, recent large-scale reviews have reported no effect of vitamin D supplementation on bone mineral density, falls or fractures.
The researchers say that clinical guidelines that continue to recommend vitamin D supplementation for bone health should be changed to reflect the best available evidence.
"Since the last major review of evidence in 2014, more than 30 randomised controlled trials on vitamin D and bone health have been published, nearly doubling the evidence base available," said Mark J Bolland from the University of Auckland.
"Our meta-analysis finds that vitamin D does not prevent fractures, falls or improve bone mineral density, whether at high or low dose.
"Clinical guidelines should be changed to reflect these findings. On the strength of existing evidence, we believe there is little justification for more trials of vitamin D supplements looking at musculoskeletal outcomes," said Bolland.
In the study, the researchers pooled data from 81 randomised controlled trials.
The majority of the trials studied vitamin D alone (ie, not prescribed in conjunction with calcium supplements) and were of one year or less.
Most included women aged over 65 (77 per cent of trials) who lived in the community and who received daily doses of more than 800 IU per day (68 per cent of trials).
There was no clinically meaningful effect of vitamin D supplementation on total fracture, hip fracture, or falls, researchers said.
There was reliable evidence that vitamin D does not reduce total fractures, hip fractures, or falls by 15 per cent -- a clinically meaningful threshold, they said.
Even when lower thresholds were assessed, there was still reliable evidence that vitamin D does not reduce falls by 7.5 per cent and total fractures by 5 per cent, according to the researchers.
In secondary analyses looking at bone density, there were small differences for lumbar spine, femoral neck, and for total body, but none of these were clinically relevant, they said.