Two recent studies say calcium and bone density don't necessarily go hand-in-hand — seemingly turning everything we know about the mineral on its head. "In the last 15 years there have been many clinical studies published, and most of them show no effect of calcium intake on fracture risk," says Mark Bolland, a senior author in both studies.
In one paper, Bolland and colleagues reviewed 59 studies on the effect of either supplements or dietary calcium (like milk or dairy) on individuals over 50. They concluded that the increased changes in bone mineral density (what's used as an indicator for your osteoporosis or fracture risk) in people who took supplements or ate calcium-rich diets were so low, it hardly made a difference in reducing the risk of fracture. The other study seemed to confirm this: Bolland's team concluded that — after analyzing 44 randomized controlled trials — the evidence for dietary calcium's protective effect in old age was "weak and inconsistent."
Bolland's two papers only looked at people over 50, but the conflicting advice on calcium isn't new: In 2013, the U.S. Preventative Services Task Force (USPSTF) changed their recommendations to advise men not to take calcium and vitamin D supplements, because the current evidence for their benefits vs. its risks was "insufficient." The supplements got an "I" rating from the USPSTF, meaning the data is too conflicting and weak.
And furthermore, Bolland says the moderate risk of bad side effects from calcium supplements outweighs its benefits; he cites gastrointestinal symptoms, constipation, kidney stones, heart attacks, and strokes. At Sweden's Uppsala University, Dr. Karl Michaëlsson echoed the sentiment, with an editorial urging clinicians to "revisit recommendations to increased intake beyond a normal balanced diet" because of the high risk of cardiovascular problems and the other side effects, and low evidence for excess calcium's actual benefit.
So when it comes to protecting your bones, Bolland says we should focus on alternative preventive measures. "Most middle-aged men are unlikely to break a bone in the short-medium term so do not need to do anything specific for their bone health, other than the usual recommendations for health of stopping smoking, maintaining a healthy body weight, having a healthy diet, and exercising regularly," says Bolland. But for men who are at a higher risk of fracture or very low bone density, he says, they can consult their doctor for effective osteoporosis medications (bisphosphonates, denosumab) that can increase bone density and prevent fractures.