Data from 388,229 men and women aged between 50 and 71 indicated that intakes exceeding 1,000 milligrams per day of calcium from supplements were associated with a 20% increase in the risk of dying from cardiovascular disease.
“Given the extensive use of calcium supplement in the population, it is of great importance to assess the effect of supplemental calcium use beyond bone health,” concluded the researchers, led by Qian Xiao, PhD, of the National Cancer Institute, Bethesda.
The study, a reanalysis of data from the National Institutes of Health-AARP Diet and Health Study, has been described as “inappropriate” by a leading dietary supplements trade association, because it was initially designed to examine the potential associations between diet and cancer.
Taylor Wallace, PhD, senior director, scientific and regulatory affairs for the Council for Responsible Nutrition (CRN), told us: “They are mining data from this cohort to address a question that it was not designed to answer.”
This is not the first report of calcium supplements taken to reduce the risk of osteoporosis may cause cardiovascular problems. However, a recent report from the Institute of Medicine concluded that “evidence from clinical trials currently does not support an effect of calcium intake on risk of cardiovascular disease”.
In addition, Harvard Medical School researchers reported in November no link between calcium supplements and an increased risk of artery calcification, according to analysis of data from the Framingham Offspring Study published in the American Journal of Clinical Nutrition.
“Benefits far outweigh the suggested detriments”
Commenting on the study’s findings, Dr. Cara Welch, senior vice president of scientific and regulatory, for the Natural Products Association (NPA), said that it is important for all age groups to maintain an adequate level of calcium as part of a healthy lifestyle.
“Dietary supplementation is both safe and effective for anyone who isn’t getting enough calcium from their diet. Calcium is an essential nutrient and the known benefits far outweigh the suggested detriments from this study,” she said.
“While this study includes a large population and a long follow-up time, it also has weaknesses in that it doesn’t capture all the pertinent information regarding duration of calcium supplementation or other nutrients.
“Additionally, the study did not find any increased risk for women taking calcium supplements so there are certainly more questions to answer before coming to a conclusion. We agree with the related commentary to this study that, in their words, ‘More large studies are needed to further assess the potential health risks or benefits of calcium supplement use.’
“The Natural Products Association does not believe that this study should cause anyone to stop taking their calcium supplements. We have long recommended that you should discuss your calcium intake with your health care professional,” added Dr Welch.
Taylor Wallace, PhD, senior director, scientific and regulatory affairs for the Council for Responsible Nutrition (CRN), said: “This is yet another study with mixed findings and inappropriate design. There is a well-established body of literature that confirms the safety of calcium.”
Dr Wallace added that what are really needed are a long-term cohort and/ or a randomized controlled trial that explicitly looks at the effects of calcium on the cardiovascular system.
A re-analysis of data from the Women’s Health Initiative (WHI), a randomized trial involving 36,282 postmenopausal women, found that calcium and vitamin D supplements were linked to a reduction in the risk of hip fracture among postmenopausal women, a no cardiovascular issues were reported, added Dr Wallace (Osteoporosis International, Feb 2013).
Dr Xiao and her co-workers analyzed data from the NIH-AARP Diet and Health Study, and identified 7,904 CVD deaths in men and 3,874 CVD deaths in women during an average 12 years of follow-up.
The data also showed that calcium supplement use was 51% in men and 70% in women.
Crunching the numbers indicated that, compared with non-supplement users, men with high intakes of supplemental calcium had significantly increased risk of CVD death, but not significantly with cerebrovascular disease death. There was no link in women.
“Whether there is a sex difference in the cardiovascular effect of calcium supplement warrants further investigation. Given the extensive use of calcium supplement in the population, it is of great importance to assess the effect of supplemental calcium use beyond bone health,” they concluded.
‘More is not always better’
In a related commentary, Susanna Larsson, PhD, from the Karolinska Institutet in Sweden wrote: “The findings from the NIH-AARP Diet and Health Study add to the mounting evidence indicating that calcium supplements may be harmful to CVD. The results are consistent with some but not all previous prospective studies on calcium supplement use in relation to CVD morbidity or mortality.
“Available data are suggestive of adverse cardiovascular effects with an excessive intake of supplemental calcium. More large studies are needed to further assess the potential health risks or benefits of calcium supplement use on CVD morbidity and mortality.
“The paradigm ‘the more the better’ is invalid for calcium supplementation.”
Sources: JAMA Internal Medicine
“Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality: The National Institutes of Health–AARP Diet and Health Study”
Authors: Q. Xiao, R.A. Murphy, D.K. Houston, T.B. Harris, W-H. Chow, Y. Park
Editorial: JAMA Internal Medicine
Are Calcium Supplements Harmful to Cardiovascular Disease?: Comment on “ Dietary and Supplemental Calcium Intake and Cardiovascular Diseases Mortality: The National Institutes of Health–AARP Diet and Health Study”
Author: S.C. Larsson
February 2013, Volume 24, Issue 2, Pages 567-580
“Health risks and benefits from calcium and vitamin D supplementation: Women's Health Initiative clinical trial and cohort study”
Authors: R. L. Prentice, M. B. Pettinger, R. D. Jackson, et al.