Two new studies published Tuesday in the journal The BMJ add to growing skepticism over whether older adults should increase calcium via supplements in order to prevent osteoporosis and risk for bone fractures.
For older adults, a daily intake of 1,000 to 1,200 mg of calcium has long been recommended. But the two papers, written by the same team of New Zealand researchers, find little evidence to support the recommendations. Recent concerns over calcium intake have emerged, suggesting that "small reductions in total fractures seem outweighed by the moderate risk of minor side effects," the study authors write. Those side effects can include constipation as well as more severe complications, like cardiovascular issues.
"Collectively these results suggest that clinicians, advocacy organizations and health policymakers should not recommend increasing calcium intake for fracture prevention either with calcium supplements or through dietary sources," the authors write.
In one study, the researchers conducted a review of randomized controlled trials looking at how extra calcium intake in women and men over age 50 affected bone mineral density. The researchers found increases in bone mineral density of about 1-2% over up to five years, but the authors say these increases are "unlikely to translate into clinically meaningful reductions in fractures." Post-menopausal women lose an average of about 1% in bone mineral density a year.
"Increasing calcium intake from dietary sources or by taking calcium supplements produces small non-progressive increases in BMD, which are unlikely to lead to a clinically significant reduction in risk of fracture," the study authors conclude.
In their other study, the researchers looked at studies on the link between calcium intake and lower risk of fractures. The studies varied in quality, but the researchers found a lack of evidence to support the relationship. "Dietary calcium intake is not associated with risk of fracture, and there is no clinical trial evidence that increasing calcium intake from dietary sources prevents fractures," the study authors write. "Evidence that calcium supplements prevent fractures is weak and inconsistent."
The researchers only found one study that supported increased calcium intake for lower fracture risk, but noted that the study, published in 1992, was in a frail population with notable vitamin D deficiency (vitamin D is also often recommended to prevent fracture in older adults). The researchers say this one study is often referenced in other research on the topic, and that studies should not rely on it given its unique population.
The new results also fall in line with the guidance provided by the United States Preventative Services Task Force in 2013. The task force reviewed studies on the use of vitamin D and calcium to prevent fractures, and ultimately concluded that, based on the evidence available, post-menopausal women should not take daily supplements.
In a corresponding editorial, Karl Michaëlsson, a professor at Uppsala University in Sweden, writes that given the lack of evidence to support increasing calcium and vitamin D intake for better bone health, the continued emphasis is "puzzling."
"The profitability of the global supplements industry probably plays its part," he argues. "Manufacturers have deep pockets, and there is a tendency for research efforts to follow the money (with accompanying academic prestige), rather than a path defined only by the needs of patients and the public."
Given growing skepticism, it's worth talking with your physician if you're currently loading up on calcium for stronger bones.