Evidence Does Not Support Vitamin D Supplements for All

Marlene Busko

November 29, 2016

The issue of whether to recommend vitamin D supplements is once again in the media spotlight following a series of articles recently published in the BMJ.

Although the US Preventive Services Task Force recommends that healthy postmenopausal women should not take calcium and vitamin D supplements to prevent fractures, other guideline groups continue to recommend vitamin D supplements, with or without calcium, to prevent falls or fractures.

For example, the United Kingdom's Scientific Advisory Committee on Nutrition (SACN) recently suggested that adults should consider taking a low-dose vitamin D supplement in autumn and winter.

However, in a new practice article published online November 23 in the BMJ, Mark J Bolland, MBChB, PhD, bone and joint research group, department of medicine, University of Auckland, New Zealand, and colleagues report that they examined the current literature and found that "there is no consistent evidence that vitamin D supplementation or raising 25-hydroxyvitaminD levels improves musculoskeletal outcomes."

They agree that people who are at high risk of vitamin D deficiency — those who are confined indoors, have very limited sunlight exposure, or have severe malabsorption syndromes — should receive counseling about getting exposure to sunlight and having a healthy diet, and then low-dose vitamin D supplements (400–800 IU/day [10–20 µg]) may be considered on an individual basis.

But "otherwise we conclude that current evidence does not support the use of vitamin D supplementation to prevent disease," Dr Bolland and colleagues surmise.

Yet in a related head-to-head article, Louis Levy, RNutr, nutrition advice team manager at Public Health England, London, United Kingdom, argues that healthy people should take vitamin D supplements in winter months, as recommended by the SACN, whereas Tim D Spector, professor of genetic epidemiology, King's College London, United Kingdom, takes the opposite stand.

Healthy People Should Take Vitamin D Pills in Winter

Mr Levy writes that the SACN reviewed the evidence for musculoskeletal health outcomes with vitamin D and "estimated that 10 μg/day is the amount of vitamin D needed for 97.5% of the population to maintain blood concentrations at or above 25 nmol/L [the level that is needed to protect musculoskeletal health] when exposure to sunshine is minimal.

"Getting enough vitamin D is particularly important because poor musculoskeletal health remains in the top 10 causes of disability adjusted life-years," he indicates.

Vitamin D is found in oily fish, red meat, liver, egg yolk, and some fortified breakfast cereals and dairy products, and it is absorbed through the skin when skin is exposed to sunlight, but many people may require a supplement to meet the recommended intake.

The SACN recommends that those who do not get much sun exposure or have darker skin should consider taking a 10 μg/day vitamin D supplement year round, and everyone should consider taking this type of supplement in the fall and winter.

However, people should avoid taking too much vitamin D, since this can result in hypercalcemia, demineralization of bone, soft-tissue calcification, and renal damage, Mr Levy cautioned.

Healthy People Should Not Take Vitamin D Pills in Winter

Dr Spector agrees that "vitamin D treatment still has a role in people with proved deficiency or in high-risk groups such as infirm elderly people or at risk-infants."

However, he is vehement that "the rest of us should avoid being 'treated' for this 'pseudodisease,' " thereby saving scarce NHS resources, and instead the focus should be "on having a healthy lifestyle, sunshine, and a diversity of real food."

According to Dr Spector, "We have unfortunately created another 'pseudodisease' that is encouraged by vitamin companies, patient groups, food manufacturers, and charities.

"Healthy people should get vitamin D from small doses of sunshine every day plus dietary sources and trust that millennia of evolution will have dealt with the fact that in northern climes our vitamin D level naturally drops in winter without us snapping our limbs," he concludes.

Unclear Benefits of Vitamin D Supplements

Meanwhile, in their review of the literature, Dr Bolland and colleagues report that more than 50 meta-analyses find there is no or little benefit from taking vitamin D supplements to prevent falls or fractures, and some trials have even reported increased risk of falls and fractures with intermittent use of high-dose vitamin D.

Combined vitamin D and calcium prevented fractures in two trials of severely vitamin D–deficient frail elderly women in residential care, but not in seven trials of community-dwelling people.

Some meta-analyses have reported positive nonskeletal effects of vitamin D supplements, but the evidence was weak.

Similarly, Dr Spector writes that most meta-analyses and Mendelian randomization studies have not shown that vitamin D prevents cardiovascular disease in humans, and the same is likely true for osteoporosis.

"Sadly," a recent Cochrane review found no overall effect of vitamin D supplementation on fractures, and "more worryingly, the studies in elderly people show no clear benefits on muscle strength or mobility," he adds.

Dr Bolland and colleagues also surmise that at least seven ongoing large randomized trials of vitamin D supplementation for nonskeletal outcomes "are unlikely to alter conclusions from the current systematic reviews," since trials are not recruiting people with severe vitamin D deficiencies.

The practice article was funded by the Health Research Council of New Zealand. All authors on the Bolland article have published randomized controlled trials and systematic reviews in the fields of vitamin D and calcium; additional disclosures are listed in the article. Mr Levy reports no relevant financial relationships; Prof Spector is the author of The Diet Myth.

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BMJ. 2016. Published online November 23, 2016. Bolland article, Levy-Spector article

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