Calcium supplements do not reduce risk of fractures

Increasing calcium intake beyond a normal balanced diet does not prevent fractures, according to two studies from New Zealand published in The BMJ on 29 September 2015.

The first study^[1]
was a systematic review and meta-analysis of 59 randomised controlled trials of dietary sources of calcium or calcium supplements, with or without vitamin D, in participants aged over 50 years. It showed that increased dietary or supplementary calcium produced only limited improvement in bone density – even when calcium was combined with vitamin D at any dose − and that these small increases were unlikely to lead to any clinically meaningful reductions in fractures.

The second study^[2]
evaluated the evidence for current recommendations to increase calcium intake through diet or calcium supplements to prevent bone fractures. It found no association between dietary calcium and risk of fracture; calcium supplements have meagre, inconsistent benefits on preventing fractures; and increased calcium intake through diet or supplements should not be recommended for fracture prevention.

“These studies confirm what is already known about the role of calcium supplements in bone health,” says Sarah Leyland, senior nurse at the National Osteoporosis Society. “Calcium supplements may increase bone density, but on their own do not reduce the risk of fractures.”

In an editorial^[3]
commenting on the studies, Karl Michaëlsson from Uppsala University, Sweden, states that the “interplay between vitamin D status and calcium intake is probably just as important in the prevention of fractures” and that an overemphasis on high intakes of calcium without firm scientific evidence has probably hindered development in this research area.

Chris Oliver, consultant trauma orthopaedic surgeon at the Royal Infirmary of Edinburgh, agrees that there has been too much emphasis on increased calcium intake without scientific evidence. “This is a common misconception also in my clinical experience treating fragility fractures,” he says. “We treat over 1,000 proximal femoral fractures per year. It would be helpful to know exactly what dose of calcium and vitamin D is most beneficial to my potential patients so that they can be advised accordingly by public health bodies.”

Leyland points out that the current UK government recommendation is that adults need a daily intake of 700mg calcium. And osteoporosis experts suggest that if people are taking an osteoporosis drug treatment, they may benefit from a daily calcium intake of around 1,000mg. “General recommendations for the adult population are to make sure you are eating a well-balanced healthy diet, providing adequate calcium and all the other nutrients needed for bone health,” she says, adding that other lifestyle factors are also important.

However, Michaëlsson highlights that recommendations from the US National Osteoporosis Foundation and the International Osteoporosis Foundation mean that the marketing of calcium and vitamin D supplements now extends to all older people with daily dietary intakes below 1,200mg calcium and 800-1,000 IU vitamin D. “By this definition virtually the whole population aged over 50 years is at risk,” he says.