On the heels of the recent study in JAMA Internal Medicine, which found that high consumption of supplemental calcium was associated with increased threat for cardiovascular disease (CVD) deaths among men (but not women), a new study published on BMJ.com suggests that high calcium intake in women was associated with higher risk of death from all causes—especially cardiovascular disease.
The study titled “Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study,” conducted by researchers from Uppsala University in Sweden, studied 61,443 Swedish women (born between 1914 and 1948) for an average of 19 years. Data were taken from the Swedish Cause of Death Registry and data on diet were taken from the Swedish Mammography Cohort. Total calcium intake analyzed included supplemental calcium, with the mean intake in the lowest quartile at 572 mg/day (the equivalent of five slices of cheese) and the highest at 2,137 mg/day.
Also, information was obtained from the women on their menopausal status, postmenopausal oestrogen therapy, parity information, weight and height, smoking habits, leisure-time physical activity and educational level.
Results found that during 19 years of follow-up, 11,944 women (17%) died: 3,862 of these (32%) died from cardiovascular disease, 1932 (16%) heart disease and 1100 (8%) from stroke. Highest rates of all-cause, cardiovascular and heart disease were observed among those with a dietary calcium intake higher than 1400 mg/day. In addition, researchers observed higher death rates among women with an intake below 600 mg/day.
Women who had a higher dietary intake of calcium exceeding 1400 mg/day and also used supplements had a higher death rate compared to those not taking supplements. Further, women with a high dietary calcium intake (>1400 mg/day) were more than twice as likely to die compared with women with a 600-999 mg/day calcium intake.
The researchers explained their findings by suggesting that diets very low or very high in calcium can override normal homeostatic control, causing changes in blood levels of calcium.
The study concluded that high calcium is associated with “higher all-cause and cardiovascular mortality rates.” Researchers recommended that when advising calcium to elderly individuals looking to prevent bone fractures, emphasis should be placed on those with a low intake of calcium rather than increasing the intake of those already consuming satisfactory amounts.
In response to these findings, The Council for Responsible Nutrition (CRN), Washington, D.C., issued a statement stressing the importance of calcium in protecting bone health, as well as questioning the negative effects of calcium on heart-health as proposed by the study.
Taylor Wallace, PhD, senior director, scientific and regulatory affairs for CRN stressed that “calcium is essential for bone health, especially if you are a postmenopausal woman at risk for osteoporosis. This study doesn’t change that fact and also demonstrates there are potential issues with too little calcium. The Institute of Medicine recommends women over 50 should obtain 1,200 milligrams of calcium daily, but also advises of a Tolerable Upper Intake Level (UL), which is the point at which no adverse effects are known, of 2,000 mg daily—from all sources, including food and supplements. This study does not change those recommendations, nor should it.”
Further, Dr. Wallace questioned the study’s findings linking CVD and calcium consumption, saying this study, nor any other, have proven this to be the case. “It’s important to understand that this study did not demonstrate a cause and effect relationship between calcium and heart health or all-cause mortality, and in fact, we are not aware of a single human study that does. There are some very specific flaws in this study, beginning with the fact that it was not set up to address the question it answered. Further, it did not adjust for the role of hormone replacement therapy (HRT), and since science has gone back and forth as to whether HRT helps or hurts the heart, the jury is out as to how this might influence the findings.”
Without a clear conclusion proving calcium to be harmful to the heart, “Consumers should be aware of how much calcium they are getting, from food and then from supplementation. However, with supplements you can clearly identify how much you are taking, while it is easier with food to forget to keep track, as you may tend to graze, with a piece of cheese here, and a glass of milk there.” Dr. Wallace suggested that consumers, “Pay attention to what you’re eating, and then supplement to fill in the gaps. Despite the way the medical journal has tried to promote this study, the fact is supplementing with calcium is a perfectly safe and reasonable approach to take. Consumers should remember to talk with their doctor or other healthcare practitioner about their individual calcium needs and what’s right for them.”