Calcium supplements risk heart health

• More evidence is emerging that women who take calcium supplements to prevent bone deterioration may, in fact, be risking their heart health.
• There is a lack of consensus currently regarding recommendations for the use of calcium supplements, which are often prescribed to older (postmenopausal) women to maintain bone health. 
• Sometimes they are combined with vitamin D, but it's still unclear whether taking calcium supplements, with or without vitamin D, can affect the heart.
• The U.S. government funded Women's Health Initiative (WHI) study - a seven-year trial of over 36,000 women - found no cardiovascular effect of taking combined calcium and vitamin D supplements, but the majority of participants were already taking personal calcium supplements, which may have obscured any adverse effects. 
• So a team of researchers in New Zealand re-analysed the WHI results to provide the best current estimate of the effects of calcium supplements, with or without vitamin D, on the risk of cardiovascular events. The researchers looked at the 16,718 women who had not been taking personal calcium supplements before entering the trial.
• It was found that women who were randomised to take calcium and vitamin D as part of the study protocol had a modest 13 to 22 percent higher risk of cardiovascular problems, particularly heart attacks. Women in the control arm had no change in risk. 
• The case against calcium became stronger when researchers added in data from 13 other, unpublished trials involving almost 30,000 women. Now the higher risk for heart attack was 25 to 30 percent and, for a stroke, 15 to 20 percent.
• The authors suspect that the abrupt change in blood calcium levels after taking a supplement causes the adverse effect, rather than it being related to the total amount of calcium consumed. High blood calcium levels are linked to calcification (hardening) of the arteries, which may also help to explain these results.
• The findings suggest that these data justify a reassessment of the use of calcium supplements in older people but further studies are needed and the debate remains ongoing.