Women who take calcium supplements to improve bone strength in middle-age could risk a 30 per cent higher risk of heart attacks, warn researchers.
A review of 11 trials suggests extra calcium can do more harm than good, even though broken bones account for thousands of deaths each year. Hundreds of thousands of women take supplements either prescribed by their doctor for osteoporosis or bought over the counter as ‘bone insurance’.
But the latest research involving 12,000 people found those taking supplements had a greater chance of suffering a heart attack. Treatment of 1,000 people with calcium for five years would cause an additional 14 heart attacks, 10 strokes and 13 deaths, and prevent 26 fractures.
In the study, published online in the British Medical Journal, people taking supplements equal to 500mg or more per day were compared with people not taking them. Those eating high-calcium diets were not at extra risk, said researchers from the universities of Aberdeen and Auckland, in New Zealand.
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. The Food Standards Agency recommends adults have 700mg of calcium a day, which should come from dietary sources including milk, cheese and green, leafy vegetables.