Calcium is not effective for the prevention of fractures, either via diet or supplements, according to research published today.
Two studies published in The BMJ lead to this conclusion, and support recent concerns over the safety of calcium supplements.
The first study, by Dr Mark Bolland, of the University of Auckland, New Zealand, and colleagues reviewed two good quality randomised controlled trials and 44 population studies of dietary calcium.
"For dietary calcium, most studies reported no association between calcium intake and fracture," they write, adding: "For milk and dairy intake, most studies also reported no associations."
"Furthermore, in 26 randomised controlled trials, calcium supplements reduced the risk of total fracture and vertebral fracture but not hip or forearm fracture," they write, pointing out that their investigations "suggested bias toward calcium supplements in the published data."
In the second study, the same team looked at whether increasing calcium intake affects bone mineral density. They analysed 59 randomised controlled trials, 15 of dietary interventions and 51 of supplements.
Raising calcium by both methods increased bone mineral density in most skeletal areas, but they conclude that this "produces small non-progressive increases in bone mineral density, which are unlikely to lead to a clinically significant reduction in risk of fracture."
Dr Bolland said last night: "Clinicians, advocacy organisations and health policymakers should not recommend increasing calcium intake for fracture prevention, either by use of calcium supplements or through dietary sources.
"For most patients who are concerned about their bone health, they do not need to worry about their calcium intake."
He said his study found that increased calcium intake led to "small, one-off" increases in bone density of up to 2%.
He said: "These increases do not build up over time and are too small to produce significant reductions in the chance of having a fracture. Secondly, the level of dietary calcium intake is not associated with the risk of having a fracture."
In an editorial, Professor Karl Michaelsson from Uppsala University in Sweden agrees with the need for a rethink. "The weight of evidence against such mass medication of older people is now compelling, and it is surely time to reconsider," he writes.
Bolland, M. J. et al. Calcium intake and risk of fracture: systematic review. BMJ 30 September 2015 doi: 10.1136/bmj.h4580 [abstract]
Tai, V. et al. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ 30 September 2015 doi: 10.1136/bmj.h4183 [abstract]
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