Calcium supplements may increase mortality:
Calcium and high-dose calcium supplementation was associated with greater cardiovascular (CV) mortality and all-cause mortality in women according to a prospective cohort study of 61,433 women born between 1914 and 1948. Compared with dietary calcium intakes of 600 to 1000 mg daily, daily intakes of ≥1400 mg were associated with significantly higher rates of death from all causes (40% increased risk), CV disease (49% increased risk), and ischemic heart disease (2 times higher risk), but not from stroke. Among the 6% of participant women using calcium supplements (500 mg), those who were also consuming >1,400 mg/d in their diet had a 2.5-times higher risk of all-cause death than women with similar total intakes not taking a supplement. (36)
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 stoke by 16%. (37)
An analysis of 388,229 individuals aged 50 to 71 years found that high calcium intake was associated with an increased risk of cardiovascular disease (CVD) mortality in men, but not women. At study enrollment, 51% of men and 72% of women were taking some form of calcium. The study found that compared to men not taking calcium, men with calcium intake of 1000 mg/day had an elevated risk of total CVD death (20% increased risk) and heart disease death (19% increased risk) but not cerebrovascular disease. In women, there was no association between calcium supplementation and death from cardiovascular disease or cerebrovascular disease. (38)