jeudi 13 août 2015

Calcium, Vitamin D For Osteoporosis: Are Recommendations Skewed By Conflicts Of Interest?

Calcium, Vitamin D For Osteoporosis: Are Recommendations Skewed By Conflicts Of Interest?

A photo illustration shows over-the-counter calcium supplements. (Bebeto Matthews/AP)

A photo illustration shows over-the-counter calcium supplements. (Bebeto Matthews/AP)

By Marina Renton
CommonHealth Intern

Might commercial influences be driving the widespread recommendation of calcium and vitamin D supplementation for the prevention and treatment of osteoporosis?

That’s the conclusion of an analysis published in the journal BMJ, written by Andrew Grey and Mark Bolland, endocrinologists and associate professors at the University of Auckland.

The analysis — strongly refuted by organizations that advocate for osteoporosis research — further complicates the already contentious issue of whether it’s a good idea to take the supplements and if so, at what dosage.

The Supplement Conundrum

Women over 50 are most likely to develop osteoporosis, a bone disease affecting millions of Americans that results in bone weakness and increased risk of fracture. Calcium and vitamin D supplements are widely recommended to prevent and treat the condition.

“But as we point out, the considerable body of randomized trial evidence doesn’t support that practice,” Grey, the study’s co-author, wrote in an email.  “We wondered why practice hasn’t changed to reflect the evidence.”

To promote bone health, over half of older Americans take calcium and vitamin D supplements, which can be prescribed by a doctor or purchased over the counter, the authors write.

The Institute of Medicine (IOM) recommends adults take in 1,000 mg of calcium per day (1,200 for adults 70+ and women 51-70) and 600 IU (international units) of vitamin D — 800 IU for the 70+ set.

As of 2013, the U.S. Preventive Services Task Force does not recommend daily calcium and vitamin D supplementation for non-institutionalized postmenopausal women to prevent fractures. This, they note, is not necessarily inconsistent with the IOM’s recommendations, which do not specifically discuss fracture prevention.

The supplements have been standard clinical practice in preventing or treating osteoporosis in older adults since the early 2000s. Since then, however, studies have emerged to contest their effectiveness, according to the paper.

The authors point to a number of recent studies and meta-analyses that have shown inconsistent results when looking at the effects of calcium, vitamin D or a combination of the supplements when it comes to fracture prevention, a main goal of osteoporosis treatment.

Plus, researchers have found evidence of negative effects of calcium and vitamin D supplementation. A couple of studies observed an increase in fracture risk, and others have seen increased risk for gastrointestinal problems, kidney stones and cardiovascular events like heart attack and stroke, the authors write.

More evidence has recently emerged questioning the benefits of vitamin D to bone health.

A JAMA Internal Medicine article earlier this month found “high-dose vitamin D supplementation in postmenopausal women was not associated with beneficial effects on bone mineral density, muscle function, muscle mass or falls,” after one year of treatment, according to the release.

“For community-dwelling older adults, increasing calcium intake, taking vitamin D supplements or combining the treatments does not safely reduce the risk of breaking a bone,” Grey wrote.

Other experts disagree.

Michael Holick, professor of medicine, physiology and biophysics at Boston University School of Medicine and a vitamin D advocate, said that assuming calcium and vitamin D are going to increase bone density — and reduce fracture risk as a result — “doesn’t really make sense.”

You build up calcium in your bones until around age 30, when your bone mass peaks, he said. After that, unless you have a certain bone disease, you can’t expect to improve bone density. But, if you’re not getting enough calcium and vitamin D from diet, then “you get it out of your bones,” resulting in a decrease in bone density, he said.

“Having adequate calcium and vitamin D over time will help maintain your bone density and reduce risk for fracture,” he said. So, stable bone density would be the best outcome to hope for.

Commercial Interests

The authors suggest that the supplements have not been proven beneficial for osteoporosis treatment, and their continued recommendation by “organizations that are ostensibly patient-focused…may be biased by the influence of companies that stand to profit from the sales of supplements, dairy products and test kits for vitamin D,” Grey wrote.

According to the analysis, sales of calcium supplements worldwide were about $6 billion in 2013 and vitamin D sales in the U.S. were $748 million in 2012. So, the authors point out, certain industries benefit from their continued popularity.

The authors looked at the sponsors of a number of osteoporosis advocacy organizations, most notably the U.S. National Osteoporosis Foundation and the International Osteoporosis Foundation. They found that over half of the organizations’ commercial sponsors were involved in nutrition-related industry. The NOF and IOF reaffirmed their support for calcium and vitamin D supplementation to prevent fractures in response to the Preventive Services Task Force’s recommendation.

“The authors question the transparency and ethical accountability of global musculoskeletal health organizations for accepting private sector funding to support their missions,” wrote Amy Porter, executive director and CEO of the NOF, in a statement. “Yet, it is exactly because of the transparency of these organizations that the authors are able to list what private sector funding is provided…NOF is committed to maintaining accountability and transparency in its collaborations with the private sector. NOF maintains its independence and objectivity in accordance with the National Health Council’s guiding principles.”

“The reality is that without this diverse funding base, most nonprofit organizations could not carry out their missions,” Porter wrote.

Regarding the NOF’s dietary supplement recommendations, Porter clarified, “[The National Osteoporosis Foundation] always advocates for getting daily recommended levels of calcium from food first and only supplementing for any shortfall in the diet.”

In response to the BMJ analysis, the IOF released a statement highlighting that its recommendations are evidence-based. Like the NOF, the IOF advocates getting calcium and vitamin D through diet when possible.

“IOF does acknowledge that there is debate about how much vitamin D and calcium is adequate and the research is ongoing,” the statements reads. “Currently IOF does not advocate that vitamin D supplements be indiscriminately prescribed for the population at large, but only for the purpose of falls and fracture prevention in adults aged over 60 years and in those at high risk who are unable to meet their vitamin D needs through exposure to sunlight.”

The IOF also disputed the article’s suggestions of bias.

“IOF is committed to maintaining accountability and transparency in its collaborations with the private sector,” the statement reads. “Under no circumstances does corporate support imply IOF’s endorsement of products or services…The sad reality for the vast majority of NGOs is that government funding is simply not available for the important work they do and they would not survive without the funds provided by corporate support.”

The statement also critiqued the evidence against vitamin D and calcium supplementation the authors present in the BMJ analysis, noting that the “evidence comes predominantly from the authors’ own research.”

The analysis concludes with a call to reduce ties between industry, academia and advocacy organizations, or at least increase the transparency of those ties.

“[I hope] that those who are involved with advocacy organizations and specialist societies consider the influence of commercial sponsors on the organizations’ policies and activities and work to eliminate the biases created by those interactions,” Grey wrote.

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