Another major study — this time a meta-analysis involving dozens of different clinical trials — has concluded that taking vitamin D supplements does nothing to protect people from bone fractures or falls. Nor does it have any meaningful effect on bone density.
The authors of the study, which was published last Friday in The Lancet Diabetes & Endocrinology, conclude there “is little justification to use vitamin D supplements to maintain or improve musculoskeletal health.” The exceptions are the rare cases when people have a disease specifically related to a vitamin D deficiency, such as rickets or osteomalacia (softening of the bones), or cases involving institutionalized people who are never exposed to the sun.
The researchers also say that current medical guidelines that recommend vitamin D supplements for bone health should be changed to reflect the reality of the scientific evidence.
And, yes, the study’s findings apply to Minnesotans and others living in northern latitudes. Most people — even in regions of the world where winter days are short or frequently overcast — get plenty of vitamin D from diet and the sun.
That’s because it doesn’t take much exposure to sunlight (just minutes a week) for the body to manufacture enough vitamin D to be healthy.
“Many patients (and doctors) have been persuaded by various studies and social media that vitamin D is a cure-all,” writes Dr. Chris Gallagher, an endocrinologist at Creighton University, in a commentary that accompanies the study.
“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,” he adds.
For the current study, a research team led by Mark Bolland, a clinical epidemiologist at the University of Auckland in New Zealand, gathered data from 81 randomized controlled trials — involving 53,537 people — that had previously investigated whether vitamin D supplements helped prevent fractures or falls or improved bone density.
Some of the studies compared high-dose vitamin D supplements with lower-dose ones. Others compared the supplements with placebos or with no treatment at all.
Most of the participants in the studies were women aged 65 and older. Those who received vitamin D were usually given at least 800 international units (IUs) of vitamin D daily.
More than half of the studies involved people whose blood tests showed they had what has been called “low” vitamin D levels — blood levels below 50 nmd/L.
Bolland and his co-authors pooled the data from the 81 clinical trials and then analyzed it. They found no evidence that vitamin D supplements had an effect on the risk of fracturing a bone anywhere in the body, including the hips. (A broken hip is the most disabling and deadly type of fracture for people aged 65 and older.) Nor did the supplements help reduce the risk of falls.
Furthermore, vitamin D supplements had no meaningful effect on bone mineral density in the spine, neck or hip.
It didn’t matter if people were treated with high or low doses of vitamin D. It didn’t matter if they took the vitamin with or without calcium. Nor did it matter if the supplements raised their vitamin D blood levels above 50 nmd/L (out of the “low” vitamin D levels).
The researchers did acknowledge, however, that few of the studies’ participants had vitamin D levels below 25 nmd/L, so more research may be needed on the effects of supplements on that small subgroup of people.
Future trials would be futile
As Bolland and his colleagues point out, their findings are consistent with other large reviews of the literature (including one published earlier this year). Their findings also support the U.S. Preventive Services Task Force recommendation that most adults should not be using vitamin D supplements to prevent falls and fractures.
Taking vitamin D supplements is not without risk. Excess amounts can cause calcium to build up in the blood, leading to fatigue, nausea, constipation, headaches and other symptoms, and may cause, over time, the development of kidney stones.
The supplement industry and other supporters of vitamin D often explain away the results of research showing vitamin D supplements to be ineffective by saying that such studies were flawed — by using too-low doses of the vitamin, for example, or by using people who already had sufficient levels of vitamin D in their bodies.
But, as Bolland and his colleagues point out, “None of those explanations seems likely to account for our findings,” in part because more recent studies have addressed those issues.
The researchers stress that we now have plenty of good, solid scientific evidence to bring the debate over vitamin D supplements to a close.
“Vitamin D supplementation did not have meaningful effects on fracture, falls, or bone mineral density, and future trials are unlikely to alter these conclusions,” they conclude. “Therefore, there is little justification for the use of vitamin D supplements to maintain or improve musculoskeletal health, and clinical guidelines should reflect these findings.”
FMI: You��ll find an abstract of the study on The Lancet Diabetes & Endocrinology website, but the full study is behind a paywall.