Calcium’s effect on heart disease and all-cause mortality

Calcium’s effect on heart disease and all-cause mortality

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A growing number of studies show increased calcium to be dangerous

I just realized that February is American Heart Disease Awareness Month. My wife pointed out that this is also International Typewriter Appreciation Month, whatever that means. When was the last time that you used a typewriter? Therefore, I thought that my last article for the month of February should focus on this most prevalent disease and the dangers of calcium in increasing the risk of heart attacks and all-cause mortality.

I wrote about a very similar topic on April 26, 2011. First, let me summarize what we knew then. At that time, a study called the Women’s Health Initiative showed that calcium supplements may cause a 20 percent rise in the risk of heart attack (BMJ. 2011 April 19;342:d2040). There were 17,000 women involved in this study with calcium. The participants who saw this modest rise in risk were taking 1000 mg of calcium supplementation. In the same paper, there was also a meta-analysis (group of three studies) that showed increases of 20 percent in both heart attacks and strokes with calcium. It did not matter whether participants were taking vitamin D or not. At the time, I hedged my bets by saying it was only one paper. The results were intriguing, though — the risk of a heart attack surpassed the benefits of reducing fracture.

Recently, several large studies reinforced the negative effects of calcium as related to the heart, and the impact seems to be even greater. Let’s examine these studies and their implications in more detail.

Calcium’s impact on women

In the Swedish Mammography Cohort, published in the same medical journal as the aforementioned study, the results showed an almost 50 percent increased risk of cardiovascular disease deaths in women who consumed more than 1400 mg of calcium from their diet, which included calcium supplements, compared to those who consumed 600 to 1000 mg (BMJ. 2013 Feb. 13;346:f228). Cardiovascular disease risk in this study included heart disease and stroke combined. The participants who consumed less than 600 mg of calcium also had an increase in mortality, but not nearly as significant as the high calcium intake group.

When you break down the percentages, the data are even more interesting. In this study, heart disease deaths increased by 114 percent. However, unlike the previous study, there was no significant increase in stroke deaths.

All-cause mortality, which means from any source, not just cardiovascular, was increased by 40 percent. Also, those women in the high calcium group had a two-and-a-half times greater risk of all-cause death when they were taking calcium supplements, while those in the same group who were not taking supplements had a much less significant (17 percent) increased risk.

Not to worry. As the authors point out, those who consume calcium without supplements are most likely to be in the ideal range. This was a large observational prospective (forward-looking) study involving over 60,000 women. The duration of the study was 19 years. However, a weakness of the study is that the overall event rate was small. The authors’ conclusion was that women should avoid calcium supplementation and get their calcium from dietary sources.

Calcium’s impact on men

Not to be left out, men also seem to be negatively affected by high calcium. The National Institutes of Health-AARP Diet and Health Study, published a week earlier than the women’s study mentioned above, showed that there was a 20 percent increased risk of cardiovascular disease death in those men who took at least 1000 mg of calcium on a daily basis compared to those who did not (JAMA Intern Med. Online Feb. 4). Again, the predominant effect was seen with death from heart disease. This was a prospective study, involving 388,000 men and women who were followed for over 12 years.

To make the data slightly more obtuse, this effect was only seen in men, not in the women involved in the study. The authors cannot explain why there was this difference in gender. However, when the data was analyzed further, and multivitamins were eliminated from the equation as a contributing source of calcium, those men taking calcium supplements of at least 1000 mg were even more likely to suffer heart disease deaths, with a 37 percent increased risk.

In my own practice, having seen several hundred patients in the last few years, it seems none of them have been deficient in calcium. Yet when many patients come for an initial visit, they are taking varying amounts of calcium supplements. One of the first things I usually do is either reduce or discontinue the dose. I then follow up with a laboratory test to make sure they are not deficient after changing their supplements.

I also educate them about foods that are good sources of calcium and explain why. Believe it or not, we absorb calcium best from plant-based sources in our diet, such as kale, almonds, tofu and unhulled sesame seeds. In an article entitled, “Do calcium supplements increase cardiovascular mortality?“ published on Feb. 21, the author, after reviewing much of the pertinent data, suggests that calcium-rich foods are the wisest and safest of choices, rather than supplementation (www.medscape.com).

Finally, in the EPIC trial, there was a decrease in the risk of a heart attack from dietary calcium (Heart. 2012; 98(12):920-925). Unfortunately, there was no effect, beneficial or not, on the number of deaths from all-cause mortality or cardiovascular disease. However, there was a noticeable 139 percent increased risk of heart attacks in calcium supplement users.

Therefore, the best way to avoid this conundrum of making sure your bones are strong and getting enough calcium, while not increasing your risk of mortality is to do several things. Make sure your vitamin D levels are sufficient, for vitamin D helps with the absorption of calcium into the bones. Most people are deficient or insufficient (a milder form) in vitamin D, so if you want to take a supplement, start here. The other is to have a well-balanced diet that includes calcium-rich foods, ensuring you are in the optimal range of daily intake and getting very little or no calcium from supplements. Lastly, don’t begin using calcium supplements before consulting with your physician.

 

Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website www.medicalcompassmd.com and/or consult your personal physician.