February 4/London/Daily Mail -- They are bought by the health-conscious to protect their bones against disease as they get older, but calcium supplements could be harming the men who take them by raising their risk of dying from heart disease, experts have warned.

A study found a 20% higher risk of death in men who take high doses. The link was not found in women.

Hundreds of thousands of adults take the supplements, either prescribed by their doctor against osteoporosis -- a disease in which bones become thinner and increasingly fragile -- or bought over the counter as ‘bone insurance’.

However, the study, involving 388,000 people, found men taking calcium supplements of more than 1,000mg a day had a greater chance of suffering heart disease and dying from it.
 
However, those achieving high-calcium diets solely through food or drink were not at extra risk, said researchers from the U.S. National Cancer Institute. It was the way supplements increase the levels of calcium circulating in the blood which appeared to have an adverse effect on the cardiovascular system.

Experts believe higher blood levels lead to hardening of the arteries, which can cause heart attacks.

Britain’s Food Standards Agency recommends adults have 700mg of calcium a day, which should come from dietary sources including milk, cheese and green, leafy vegetables.

Women had no such extra risk, says a report in JAMA Internal Medicine, although some previous trials have found a link. Researchers followed men and women aged 50-71 over an average of 12 years. They recorded 7,904 deaths in men from cardiovascular disease and 3,874 deaths in women.

Supplements containing calcium were used by 51% of men and 70% of women.

Men taking 1,000mg or more in calcium supplements a day had an almost 20% higher rate of heart disease and death than those who did not take supplements.

The report said, "Whether there is a sex difference in the cardiovascular effect of calcium supplements warrants further investigation.

"Given the extensive use of calcium supplements in the population, it is of great importance to assess its use beyond bone health."

Older women are more at risk of osteoporosis because the rate of  bone loss is accelerated by the menopause. One in two women and one in five men over the age of 50 will break a bone mainly because of the disease.