Large Review Finds Vitamin D Ineffective in Preventing Fractures, Falls

A large meta-analysis did not find any beneficial effects to vitamin D supplementation for reducing fractures, falls, and bone mineral density, according to a recent study published in The Lancet Diabetes and Endocrinology.

It is the largest such study to date.¹ The researchers also said the study found no differences in the effects of higher versus lower doses of vitamin D. They also said there is little justification for the use of vitamin D supplements to maintain or improve bone health, except for the prevention or treatment of rickets and osteomalacia in high-risk groups. Clinical guidelines should reflect their findings, they said.

The authors searched 3 databases using the search term “vitamin D” and additional keywords on 2 separate days, and assessed randomized controlled trials of adults that compared vitamin D with untreated controls, placebo, or lower-dose vitamin D supplements.

Eligible studies included outcome data for total or hip fractures, falls, or bone mineral density measured at the lumbar spine, total hip, femoral neck, total body, or forearm. The co-primary endpoints were participants with at least 1 fracture, at least 1 hip fracture, or at least 1 fall. The secondary endpoints were the percentage change in bone mineral density from baseline at lumbar spine, total hip, femoral neck, total body, and forearm.

The researchers found 81 trials (n = 53537 participants) that reported fracture (n = 42), falls (n = 37), or bone mineral density (n = 41).

The majority of the trials studied vitamin D alone (ie, not prescribed with calcium supplements) and were of 1 year or less. Most included women aged over the age of 65 (77% of trials) who received daily doses of more than 800 IU per day (68% of trials).

More than half of the trials were done in populations with baseline concentrations of 25-hydroxyvitamin D (25OHD) of less than 50 nmol/L (an indicator of low vitamin D levels), but only 6% were done in populations with vitamin D deficiency.

The majority of trials (91%) reported achieving 25OHD concentrations of 50 nmol/L or more, and about half reported achieving 25OHD concentrations of 75 nmol/L or more.

There was no clinically meaningful effect of vitamin D supplementation on total fracture, hip fracture, or falls. There was reliable evidence that vitamin D does not reduce total fractures, hip fractures, or falls by the threshold of 15%. Even when lower thresholds were assessed, there was still reliable evidence that vitamin D does not reduce falls by 7.5% and total fractures by 5%.

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. In addition, the authors conducted more than 60 subgroup analyses to verify their findings.

The study had some limitations. The data were collected differently for falls in different trials, which might affect the findings. While the authors rated all trials for risk of bias, there were methodological limitations in some of the trials.

In addition, smaller trials of shorter duration tended to find stronger effects of vitamin D compared to larger trials of longer duration.

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

Older adults have long been pushed to take vitamin D supplements, noted an accompanying commentary, which said the final answer on this subject may come in 3 years, when results from a randomized, placebo-controlled trial of 100,000 people taking vitamin D will be released.²

Reference

1. Bolland MJ, Grey A, Avenell A. Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis. [published online October 4, 2018]. Lancet Diabetes Endocrinol. doi: 10.1016/ S2213-8587(18)30265-1.

2. Gallagher JC. Vitamin D and bone density, fractures, and falls: the end of the story? [published online October 4, 2018]. Lancet Diabetes Endocrinol. doi: 10.1016/S2213-8587(18)30269-9.