Over the past few years there have been several studies suggesting calcium supplements increase the risk of cardiovascular disease events, however the majority of these observational studies depend entirely on recall of supplement use, and do not distinguish between different forms of calcium.
This makes the evidence from these studies low on the scale of reliability, however it is reassuring to have a study with more positive results.
A Canadian study published online May 23rd in the Journal of Clinical Endocrinology and Metabolism found in those women who were taking calcium supplements up to 1000 mg per day, as opposed to no supplements, there appeared to be a reduction in mortality. And there was a similar trend in individuals who were getting calcium from dietary sources rather than from supplements
The findings are reassuring, said Dr. Goltzman, because some prior research "has suggested that cardiovascular events — heart attacks and strokes — could be increased by calcium supplements." And the new results are consistent with other findings from the Women's Health Initiative*, which also found a slight reduction in all-cause mortality with calcium, as did the Iowa Women's Health Study, he noted. These findings were only found in women.
However, the current research did not produce any conclusive evidence about vitamin D, Dr. Goltzman said. "We couldn't say there was any adverse or beneficial effect of vitamin D on all-cause mortality."
* The Women's Health Initiative (WHI) double-blind, placebo-controlled clinical trial randomly assigned 36,282 postmenopausal women in the U.S. to 1,000 mg elemental calcium carbonate plus 400 IU of vitamin D(3) daily or placebo showed
"Among women not taking personal calcium or vitamin D supplements at baseline, the hazard ratio [HR] for hip fracture occurrence in the CT following 5 or more years of calcium and vitamin D supplementation versus placebo was 0.62 (95 % confidence interval (CI), 0.38-1.00). In combined analyses of CT and OS data, the corresponding HR was 0.65 (95 % CI, 0.44-0.98). Supplementation effects were not apparent on the risks of myocardial infarction, coronary heart disease, total heart disease, stroke, overall cardiovascular disease, colorectal cancer, or total mortality, while evidence for a reduction in breast cancer risk and total invasive cancer risk among calcium plus vitamin D users was only suggestive."
Another recently published study, entitled Calcium intake and serum concentration in relation to risk of cardiovascular death in NHANES III, included serum calcium levels to estimated intake and found
"There was increased risk of overall CVD death for those in the bottom 5% of serum calcium compared to those in the mid 90% (HR: 1.51 (95% CI: 1.03-2.22)). For women there was a statistically significant increased risk of IHD death for those with serum calcium levels in the top 5% compared to those in the mid 90% (HR: 1.72 (95%CI: 1.13-2.61)), whereas in men, low serum calcium was related to increased IHD mortality (HR: 2.32 (95% CI 1.14-3.01), Pinteraction: 0.306). No clear association with CVD death was observed for dietary or supplemental calcium intake."
The conclusion from this study was
"Calcium as assessed by serum concentrations is involved in cardiovascular health, though differential effects by sex may exist. No clear evidence was found for an association between dietary or supplementary intake of calcium and cardiovascular death."
