Studies recently released on calcium safety are helping to rebuild consumer confidence that the mineral will not cause cardiovascular disease (CVD). A 2012 study published by the British Medical Journal (BMJ. 2011 April. doi: 10.1136/bmj.d2040) linked calcium supplementation and CVD risk in women, with researchers noting they found the highest rates of death among women with higher calcium intakes. However, a number of more recent studies have debunked the association between calcium and CVD risk by illustrating promising results among large cohorts of women supplementing with the nutrient.
One study assessed 74,245 women in the Nurses’ Health Study with 24 years of follow-up, and every four years, calcium supplement intake was evaluated (Osteoporos Int. 2014 August. doi: 10.1007/s00198-014-2732-3). Women in the study were free of CVD and cancer at baseline, and those who took calcium supplements had higher levels of physical activity, smoked less and had lower trans-fat intake compared to those who did not take calcium supplements. During the 24-year follow-up period, 4,565 cardiovascular events occurred (2,709 coronary heart disease [CHD] and 1,856 strokes). After researchers factored in the women’s ages, body mass indexes, dietary calcium and vitamin D intakes, and other CVD risk factors, the relative risk of CVD for women taking more than 1,000 mg/d of calcium supplements compared to those taking none equaled 0.82 (95 percent confidence interval [CI] 0.74 to 0.92; p for trend <0.001). Also, for women taking more than 1,000 mg/d of calcium supplements compared to those taking none, the multivariable-adjusted relative risk for CHD equaled 0.71 (0.61 to 0.83; p for trend<0.001) and for stroke equaled 1.03 (0.87 to 1.21; p for trend=0.61). Therefore, the researchers found supplement intake did not significantly increase CVD risk in women. Relative risks were also similar in analyses limited to non-smokers, women without hypertension and women who had regular physical exams.
Another study came out in July to further back calcium’s safety for post-menopausal women (Journal of Bone and Mineral Research. 2014 July. doi: 10.1002/jbmr.2311). The researchers assessed 63,563 participants through 18 separate reports from 1966 to 2013, which indicated 3,390 CHD events and 4,157 deaths occurred during the period. Study authors calculated the relative risk of CHD events and all-cause mortality from calcium supplementation (with or without vitamin D) using data from the reports and a random-effects meta-analysis. Through their analysis, the researchers concluded current evidence does not support previous claims that supplementing with calcium could increase CVD risk or all-cause mortality in older women.
Regarding the July report from the Journal of Bone and Mineral Research, Andrea Wong, Ph.D., Council of Responsible Nutrition’s (CRN) VP of scientific & regulatory affairs, said it’s important to note researchers only assessed studies where CHD outcomes were reported and followed up by confirmation through hospital records or clinical review. Older study designs relied on self-reporting only, making them prone to error. When reviewing the BMJ article questioning calcium’s safety, Wong further noted how the study was not actually designed to look at the relationship between calcium supplementation and CVD risk, but rather, the increased risk was a secondary observation. This means researchers did not take other variables into account, and the data holds limited value.
“The (BMJ) study was not intended to look at calcium’s safety at all, so it did not offer strong evidence for what it claimed," Wong said. “So now, it’s important to ensure consumers that they can have confidence in taking their calcium supplements, as these most recent studies really reinforce the safety of calcium supplementation, particularly for women who are at risk for osteoporosis."
Corey Hilmas, senior vice president of scientific and regulatory affairs, Natural Products Association (NPA), also pointed out flaws within the BMJ study. He noted the researchers used a dataset that was not completely available to them; they only had access to what was publically available, which is usually insufficient as sound evidence. In addition, the study failed to demonstrate crucial factors that make up sound research relative to a risk factor (in this case, calcium supplementation), which include dose-dependence, time dependence and plausible mechanism of action.
A meta-analysis such as the one used in the BMJ study may work when looking for a potential signal that calcium could cause CVD, but a good prospective study must follow and look for particular adverse events, Hilmas explained. Unfortunately, consumers can too often jump to conclusions when they see a study questioning their long-trusted products, despite the study’s quality level.
“With all of these studies, your average consumer doesn’t know the difference between good and bad (research), the weaknesses that are inherent in a retrospective study, and how to interpret those results," Hilmas said. “All they see is the bottom line."
As with all research studies, the proof is in the pudding. Calcium safety research articles will continue to roll out in the future, and these most recent studies should help alleviate consumer concerns and show calcium supplementation with or without vitamin D will not cause them harm. Both nutrients are crucial in the diets of post-menopausal women, especially for decreasing the risk of fractures and helping them maintain quality of life into their later years.
For more information and the latest studies backing bone/joint ingredients, visit INSIDER’s Joint Health Content Library.