Research shows, calcium supplements taken by many older people could be increasing their risk of a heart attack. The study, published in the British Medical Journal, said people who took supplements were 30 per cent more likely to have a heart attack. In all 12,000 people aged over 40 took part in the trials of calcium supplements of 500mg or more a day. The risk of heart attack was seen across men and women, was independent of age and the type of supplement given. The reason for the increased risk of heart attack is not clear but it is thought the extra calcium circulating in the blood could lead to a hardening of the arteries.The researchers said those who had a diet naturally high in calcium were at no increased danger. The study was done in the University of Aberdeen by Dr Alison Avenell with colleagues in New Zealand and the US.