New research has cast doubt on whether people should take calcium supplements to ward off the degenerative bone disease osteoporosis.

It is standard medical advice for people to take calcium supplements if they are not getting the recommended intake of calcium in their diet every day.

But a new review of studies published in the British Medical Journal has suggested it could lead to an increased risk of heart attacks.

A recent New Zealand study suggested a link between calcium and heart attacks, so researchers from the University of Auckland reviewed 11 studies of people taking calcium, without taking vitamin D.

All up there were almost 12,000 people in the studies.

Professor Ian Reid from the Department of Medicine at the University of Auckland says differences in study design and quality were taken into account to minimise bias.

His review found calcium supplements were associated with about a 30 per cent increased risk of heart attack and smaller, non-significant increases in the risk of stroke and mortality.

The findings were consistent across trials and were independent of age, sex and type of supplement.

Professor Reid says although the increase was modest, it could translate into large numbers across the population.

Review in doubt

But experts from Osteoporosis Australia have cast doubt on the findings.

In a statement on their website, it says the weight of evidence to date indicates no increased risk of heart attacks from taking calcium supplements.

They say a number of long-term studies have found that calcium can actually protect the heart, such as the Nurses Study of 85,000 women.

Osteoporosis Australia says calcium supplements are an effective way of reducing fracture risk and bone loss in older men and women who have a diet low in calcium.

Professor Reid says ultimately, any potential risks of calcium need to be weighed against the benefits of the supplements to prevent osteoporosis.

"Given the modest benefits of calcium supplements on bone density and fracture prevention, a reassessment of the role of calcium supplements in osteoporosis management is warranted, they conclude," he said.

An accompanying editorial by Professor John Cleland of the University of Hull in the UK and colleagues suggests that there are doubts about the efficacy of calcium supplements in reducing fractures.

He says that on the basis of the limited evidence available, patients with osteoporosis should generally not be treated with calcium supplements, either alone or combined with vitamin D, unless they are also receiving an effective treatment for osteoporosis for a recognised indication.

Osteoporosis Australia recommends women under 50 get 1,000 milligrams a day of calcium, rising to 1,300 in women over 50.

Men aged 19 to 70 should get 1,000mg a day, rising to 1,300 for men over 70.