In a new analysis from the National Institutes of Health, men who took calcium tablets were more likely to die of heart disease over more than a decade than those who didn’t get extra calcium in supplement form.
“The effect of supplemental or dietary calcium on heart disease has always been a bit of an unanswered story,” said Howard Sesso, a preventive medicine researcher at Brigham and Women’s Hospital and Harvard Medical School in Boston.
“It could be that when you take supplements, maybe you’re taking doses that far exceed what you need,” he added. But it’s still unclear how that might raise cardiovascular risks.
The new findings are based on a study of close to 400,000 middle-aged Americans initiated in 1995 to 1996.
Study volunteers answered questions about their lifestyle, general health and diet, including use of supplements. Researchers then tracked how many of them died, and from what causes, over the next 12 years.
About half of men and more than two-thirds of women said they took calcium supplements or multivitamins containing calcium at the outset.
During the study period, almost 12,000 people - or about three percent - died of cardiovascular disease.
Qian Xiao from the National Cancer Institute and her colleagues found men who took 1,000 milligrams of calcium per day or more were 20 percent more likely to die of heart-related causes than those who passed on calcium supplements. That was after the researchers took into account men’s age, race and weight, as well as other measures of diet and lifestyle.
However, there was no link between calcium supplements and heart disease deaths in women. And calcium from food and beverages wasn’t tied to heart problems in men or women, the research team wrote Monday in JAMA Internal Medicine.
It’s possible that calcium build-up in the arteries and veins may affect cardiovascular risks in some people, Xiao wrote in an email to Reuters Health.
NO CAUSE-EFFECT LINK
But Sesso, who wasn’t involved in the new study, told Reuters Health he wasn’t sure why, biologically, calcium supplements would be linked to a higher risk of heart problems in men but not women.
The findings don’t prove a cause-and-effect link between the supplements and heart problems. It’s possible there were certain differences between men who did or didn’t take extra calcium that the research team couldn’t measure.
“Although we observed an increased risk of death from heart disease in men who reported taking supplements containing calcium, we cannot say for sure that it was a result of using those supplements,” Xiao said.
According to Sesso, the study won’t change the fact that calcium supplements are typically recommended for reasons not related to heart disease - such as to prevent fracture risk in older adults who don’t get enough calcium through food.
Eating a balanced diet and keeping a healthy weight are as or more important than any supplement when it comes to cardiovascular health, Sesso said.
“If you have a good diet in the first place, a supplement might not be adding all that much,” he said.
SOURCE: JAMA Internal Medicine, online February 4, 2013
Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality
The National Institutes of Health–AARP Diet and Health Study
Main Outcome Measures Dietary and supplemental calcium intake was assessed at baseline (1995-1996). Supplemental calcium intake included calcium from multivitamins and individual calcium supplements. Cardiovascular disease deaths were ascertained using the National Death Index. Multivariate Cox proportional hazards regression models adjusted for demographic, lifestyle, and dietary variables were used to estimate relative risks (RRs) and 95% CIs.
Results During a mean of 12 years of follow-up, 7904 and 3874 CVD deaths in men and women, respectively, were identified. Supplements containing calcium were used by 51% of men and 70% of women. In men, supplemental calcium intake was associated with an elevated risk of CVD death (RR>1000 vs 0 mg/d, 1.20; 95% CI, 1.05-1.36), more specifically with heart disease death (RR, 1.19; 95% CI, 1.03-1.37) but not significantly with cerebrovascular disease death (RR, 1.14; 95% CI, 0.81-1.61). In women, supplemental calcium intake was not associated with CVD death (RR, 1.06; 95% CI, 0.96-1.18), heart disease death (1.05; 0.93-1.18), or cerebrovascular disease death (1.08; 0.87-1.33). Dietary calcium intake was unrelated to CVD death in either men or women.
Conclusions and Relevance Our findings suggest that high intake of supplemental calcium is associated with an excess risk of CVD death in men but not in women. Additional studies are needed to investigate the effect of supplemental calcium use beyond bone health.
In Western countries, great emphasis has been put on calcium intake because of its proposed benefit for bone health. Calcium supplementation has become widely used, especially among the elderly population. A recent study1 reported that more than 50% of older men and almost 70% of older women in the United States use supplemental calcium. However, beyond calcium’s established role in prevention and treatment of osteoporosis, its health effect on nonskeletal outcomes, including cardiovascular health, remains largely unknown and has become increasingly contentious.
Qian Xiao, PhD; Rachel A. Murphy, PhD; Denise K. Houston, PhD; Tamara B. Harris, MD; Wong-Ho Chow, PhD; Yikyung Park, ScD
During 3 549 364 person-years of follow-up, we identified 7904 CVD deaths in men and 3874 CVD deaths in women. Overall, 23% of men and 56% of women took individual calcium supplements, and 56% of men and 58% of women took multivitamins containing calcium. Compared with participants in the lowest quintile of dietary calcium intake or nonusers of calcium supplement, those in the highest quintile or supplement users were more likely to be non-Hispanic white, to have a college education, to have self-rated their health as being excellent, to be physically active, to use multivitamins, and to have higher intakes of fruits and vegetables and whole grains, but they were less likely to smoke or have a history of hypertension and had lower consumption of alcohol, red meat, and total fat. Compared with women who were nonusers, women who used calcium supplement had a lower BMI and were more likely to use menopausal hormone therapy.
In both men and women, dietary calcium intakes were inversely associated with both total CVD and heart disease mortality in age-adjusted models . However, after adjusting for potential CVD risk factors, the associations were substantially attenuated and became null in women. Among factors controlled in the multivariate model, variables related to smoking were the strongest confounders. Restricting analyses to supplemental calcium nonusers did not change the associations between dietary calcium intake and CVD mortality (data not shown).