The latest flip-flop in health has to do with calcium. For decades, doctors, nutrition experts and registered dietitians have been urging women to take calcium supplements to strengthen their bones. A new study shows that advice was likely misguided.
Do Calcium Supplements Calcify Arteries?
In this trial, the Multi-Ethnic Study of Atherosclerosis (MESA), 5,448 adults who did not have heart disease were followed up for 10 years (Journal of the American Heart Association, October 11, 2016). Researchers had them fill out questionnaires about their diet and supplements. They also underwent scans of their coronary arteries to see how much calcification they had. This is a measure of heart attack risk.
The authors found that “calcium supplement use was associated with a 22% increase in risk in incident CAC” [coronary artery calcification]. When people take calcium pills, their blood levels rise rapidly. This can lead to what doctors call “calcium loading” or excessive calcium throughout the blood stream. This in turn appears to contribute to atherosclerosis.
Plaque in the coronary arteries contains much more calcium than cholesterol. That’s why scans for coronary artery calcification can help predict the risk of heart disease and future heart attacks. The authors speculate that calcium from supplements may also affect insulin metabolism, inflammation, cholesterol and triglycerides.
Calcium from Food Is Protective:
Not all calcium is dangerous. In fact, the results of the MESA study show that people who got the highest amounts of calcium from their diet were least likely to have calcified coronary arteries. They had a 27% reduced risk for hardened arteries.
What this means is that mom was right when she encouraged you to drink your milk, eat your yogurt and consume lots of green leafy vegetables. These dietary sources of calcium appear to be good for the circulatory system.
Are Calcium Pills Bad for Bones?
The assumption that calcium pills would strengthen bones and prevent osteoporosis appears to have been built on a house of cards. Because bones have a lot of calcium, people thought that taking supplements would make bones stronger. But excessive calcium disrupts a crucial hormone that regulates calcium flow in and out of bone tissue. Calcium loading seems to interfere with the normal activity of this parathyroid hormone. One possibility is that high calcium levels suppress natural bone remodeling, which is how bones stay strong (Nutrients, Oct, 2013).
Last year a meta-analysis involving 50 controlled trials and more than 12,000 study subjects concluded that calcium supplements “are unlikely to translate into clinically meaningful reductions in fractures” (BMJ, Sept. 29, 2015). In the same issue of the BMJ, a separate analysis found that “Evidence that calcium supplements prevent fractures is weak and inconsistent” (BMJ, Sept. 29, 2015).
The Handwriting on the Wall:
For decades thoughtful scientists have been warning that taking high-dose calcium pills is not a good way to build strong bones and prevent fractures. Here is what we wrote about this topic last year. https://www.peoplespharmacy.com/2015/10/01/calcium-supplements-do-not-prevent-broken-bones/
It must be especially frustrating for people who have been conscientiously trying to protect their bones to learn that instead they have may have been putting their hearts at risk. Calcium pills have other downsides as well. Research has been building that excess calcium may increase the risk for kidney stones (New England Journal of Medicine, Feb. 16, 2006) and severe constipation (Journal of Bone Mineral Research, March, 2012) in addition to a greater risk of heart attacks (BMJ, July 29, 2010) and dementia (Neurology, online Aug. 17, 2016). Read more about this most recent concern:
What Are We to Make of the Calcium Flip-Flop?
By now, it should be apparent that the calcium advice of the last 30 years leaves a lot to be desired. Not only is the benefit of supplements questionable, there is reason to be concerned about risks.
In 2010 we interviewed Walter Willett, MD, DrPH, Chairman of the Department of Nutrition and Frederick John Stare Professor of Epidemiology and Nutrition at Harvard University’s T. H. Chan School of Public Health. He and Michael Castleman suggested that a diet rich in vegetables would be a better approach to keeping bones healthy than calcium supplements. People don’t need pills to have strong bones. Here is a link to the one-hour Show 752: Bone Vitality. The MP3 download is $2.99.
What do you think about this calcium controversy? We would love to read your thoughts in the comment section below.