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Vitamin D supplements really don’t stave off falls or boost bone mineral density

No justification for using them anymore, except for rare conditions, say authors of largest meta-analysis to date

Caroline White

Friday, 05 October 2018

Vitamin D supplementation, irrespective of dose, does not stave off fractures or falls, or improve bone mineral density in adults, concludes the largest meta-analysis* to date of the available evidence, published today in The Lancet Diabetes & Endocrinology.

There is therefore little justification for using these supplements to maintain or boost musculoskeletal health, except for the prevention of rare conditions such as rickets and osteomalacia in high risk groups, conclude the authors.

Clinical guidelines that continue to recommend vitamin D supplementation for bone health should be changed to reflect the best available evidence, they add.

Vitamin D supplements have long been recommended for older people to treat or stave off osteoporosis, with some early evidence suggesting benefits for bone health. But recent large-scale reviews have cast doubt on the role of vitamin D supplementation in this regard.

The authors pooled data from 81 randomised controlled trials, most of which looked at vitamin D alone─ not prescribed in conjunction with calcium supplements─ and lasted one year or less. Most included women aged over the age of 65 (77% of trials) who were living independently and who received daily doses of more than 800 IU daily (68% of trials).

More than half of the trials included those with baseline concentrations of 25-hydroxyvitamin D (25OHD) of less than 50 nmol/l (often considered to indicate low vitamin D levels), but only 6% included people who were vitamin D deficient (a baseline 25OHD of less than 25 nmol/l). Most trials (91%) reported achieving 25OHD levels of 50 nmol/l or more, and about half reported achieving levels of 75 nmol/l or more.

Vitamin D supplementation made no difference to the risk of all fractures, hip fracture, or falls. There was reliable evidence that vitamin D didn’t reduce the risk of fractures, hip fractures, or falls by 15%—a clinically meaningful threshold. Even when lower thresholds were assessed, there was still reliable evidence that vitamin D didn’t reduce falls by 7.5% and total fractures by 5%.

Secondary analyses looking at bone density indicated small differences for lumbar spine, femoral neck, and for total body, but none of these was clinically relevant. The authors carried out more than 60 subgroup analyses to verify their findings.

While the authors rated all trials for risk of bias, there were methodological limitations in some of them. And smaller trials of shorter duration tended to find stronger effects of vitamin D than larger trials of longer duration.

Because of the small number of trials with baseline 25OHD below 25 nmol/l (831 participants), more research might be needed into the effect of vitamin D supplementation at these levels, they suggest.

“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,” comments lead author Dr Mark Bolland, University of Auckland, New Zealand.

“Our meta-analysis finds that vitamin D does not prevent fractures, falls or improve bone mineral density, whether at high or low dose... On the strength of existing evidence, we believe there is little justification for more trials of vitamin D supplements looking at musculoskeletal outcomes.”

In a linked comment**, J Chris Gallagher, of Creighton University Medical Centre, Omaha, USA, says: “The context for this analysis lies in the fact that many patients (and doctors) have been persuaded by various studies and social media that vitamin D is a cure-all. This thinking is reminiscent of the fervour that supported the widespread use of vitamin A, vitamin C, and vitamin E years ago, and all of those vitamin trials later proved to be clinically negative…

“Already I can hear the fervent supporters—what about the extra-skeletal benefits of vitamin D? Within three years, we might have that answer because there are approximately 100 000 participants currently enrolled in randomised, placebo-controlled trials of vitamin D supplementation. I look forward to those studies giving us the last word on vitamin D.”

*Bolland, MJ, Grey A, Avenell A. Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis. The Lancet Diabetes & Endocrinology, October 04, 2018. DOI:10.1016/S2213-8587(18)30265-1
**Gallagher JC. Vitamin D and bone density, fractures, and falls: the end of the story? The Lancet Diabetes & Endocrinology, October 04, 2018. DOI:10.1016/S2213-8587(18)30269-9

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