Studies question calcium supplements and drug benefits
Conventional wisdom about osteoporosis treatment has been shaken by results from three studies, revealed this month. Calcium isn’t as effective or safe as previously thought, and millions of people may be taking unnecessary preventative treatments.
Calcium supplements have long been prescribed to elderly women to prevent bone loss. They are thought to reduce bone ’turnover’, where calcium is reabsorbed into the body. But a five year study from the University of Western Australia, led by Richard Prince, has now concluded that while the supplements alone are initially successful, after three to five years the reduction in bone turnover was no better than in placebo trials.
’But there is good news,’ says Prince. ’Our five-year study has shown that a combination of calcium and vitamin D prevented bone loss for the duration of the study.’ The study showed that taking vitamin D along with calcium kept bone mineral density constant for the five year period - equating to a drastic reduction in bone turnover. The researchers think vitamin D helps reduce reabsorption of calcium into the body, and also suppresses parathyroid hormone, which regulates calcium levels in the body by transferring bone calcium into the blood.
That study will be published in the Journal of Clinical Endocrinology & Metabolism in March.
But the use of calcium itself is called into question by a study from New Zealand which links calcium supplements to an increased risk of heart attack.
The study, led by Ian Reid at the University of Auckland, New Zealand, investigated over five years the occurrence of heart attacks and other cardiovascular problems in healthy postmenopausal women taking calcium supplements. They saw a relatively higher proportion of events in the sample taking the supplements - 45 in 31 women as opposed to 19 events in 14 women not taking calcium.
’These adverse trends have been present in a number of other recent studies,’ Reid told Chemistry World. ’This is a well established problem associated with calcium use in dialysis patients. These observations suggest that our findings are correct, not just a chance finding.’
While these studies test the efficacy of treatments, a third study, published in the British Medical Journal (BMJ) this month, suggests that pharmaceutical firms have greatly exaggerated the benefits of drugs to combat pre-osteoporosis, also called osteopenia.
The work examines studies of osteopenia drugs funded by pharmaceutical firms, and concludes that they give potentially misleading information regarding the effectiveness. One study of popular drug raloxifene cites a 75 per cent reduction in ’relative risk’. But that is only a 0.9 per cent reduction in absolute risk, the authors say - meaning treating 270 women with the drug would prevent just a single vertebral fracture.
’The problem is that the definitions of osteoporosis and osteopenia are really just arbitrary - a line was drawn on a graph in the early 90s by a committee working with a drug company,’ Ray Moynihan, conjoint lecturer at the University of Newcastle, Australia, and co-author of the paper, told Chemistry World. ’One of the key reforms needed is disentanglement of doctors and drug companies - the closeness between so-called osteoporosis experts and the companies making osteoporosis drugs makes it very hard to find the truth.’
The ’line on a graph’ Moynihan refers to separates healthy people, those with osteopenia and those with osteoporosis by bone mass density (BMD), a measure of bone strength. The National Osteoporosis Society (NOS) maintains that BMD is an important factor in diagnosing the diseases, along with family histories, lower levels of oestrogen or testosterone and long term use of corticosteroids.
’In the UK, almost one in two women and one in five men over the age of 50 will break a bone because of osteoporosis,’ said Claire Severgnini, chief executive of NOS. ’The NOS believes it is crucial to treat those at the risk of osteoporosis before they break that first bone.’
1 Zhu et al, J Clin. Endocrin. Metab. 2 Bolland et al, BMJ 3 Alonso-Coello et al, BMJ336
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