Calcium supplements increased the risk of cardiovascular events, especially heart attacks, in older women. A re-analysis of data from the Women’s Health Initiative Calcium/Vitamin D Supplementation Study found that among the almost 16,718 women not taking personal supplements at the time of randomization, being randomized to new supplement use (1g calcium and 400 IU vitamin D daily) was associated with a statistically significant increase in risk of cardiovascular events (heart attack, stroke) ranging from 13%-22%. Among women already taking supplements at the start of the study, no such increase in events was seen. A meta-analysis of 3 placebo-controlled trials found that compared to placebo, calcium and vitamin D increased the risk of heart attack by 21%, stroke by 20%, and heart attack or stroke by 16%. (85)
