Then a randomized, controlled trial of 1,471 healthy women found that the group taking 1 g/day of calcium citrate showed a doubling in risk for MI and a trend toward higher risk of angina, compared with the placebo group (BMJ. 2008;336:262-6). The investigators in that study re-analyzed the WHI data and found a 22% increase in risk for MI in women who at baseline had no personal calcium use (BMJ 2011;19:342:d2040).
There were significant differences in the comparison groups in the re-analysis, including differences in personal history of MI, Dr. Sellmeyer noted. "Whether this truly represents an increased risk or not is unclear," she said.
Another study by some of the same investigators "got a ton of press" even though it was a relatively small meta-analysis, she added. The attempted meta-analysis of 190 trials of calcium supplementation yielded 15 eligible trials, but most of the data came from 5 trials. The meta-analysis reported a 31% increase in risk for MI in calcium supplement users, with possibly a higher risk in those taking more than 1,600 mg/day (BMJ 2010;341:c3691).
"It’s really hard to know at this point" whether the risk of vascular calcification from supplementation is significant, Dr. Sellmeyer said. "I think it does behoove us to be judicious with our calcium and not let people consume more calcium than we think is really beneficial."
Calcium citrate probably is a little better absorbed than calcium carbonate and may be a little less constipating, "but for a lot of people it doesn’t matter," she said.
As always, physicians should be alert for conditions in their patients that might warrant higher intakes of calcium or vitamin D, she said, including malabsorption (as in patients who underwent gastric bypass surgery), healing osteomalacia, fracture healing, anabolic therapy, postoperative hyperparathyroidism, hypoparathyroidism, or adolescence.
Dr. Sellmeyer said she has no relevant conflicts of interest.