One of the biggest flip-flops in modern healthcare disappeared without a trace. For decades, doctors, nutrition experts and registered dietitians have been urging women to take calcium pills to strengthen their bones. It was assumed that extra calcium was totally safe and highly effective. Then studies suggested that too much extra calcium might lead to calcification of soft tissue and actually increase the risk of cardiovascular complications. A reader wants to know about how calcium is affecting her soft tissue.
Q. Since 1995 I have been taking calcium supplements to keep my bones strong. I was shocked and surprised when an ultrasound done on my clavicles for deltoid pain revealed calcium deposits in my soft tissue! Are my calcium supplements responsible?
A. This question should have a simple, straightforward answer. Unfortunately, it does not.
Do Calcium Supplements Calcify Arteries?
In 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].
How Safe Are Calcium Pills:
A study published in JACC Cardiovascular Imaging (Jan. 2021) analyzed data from 9 randomized clinical trials. The authors concluded:
“Oral calcium supplementation may increase calcium deposition in the coronary vasculature independent of changes in atheroma volume.
“…we demonstrate for the first time a statistically significant independent association between oral calcium supplementation and progressive coronary arterial calcification.”
In the same issue of JACC Cardiovascular Imaging (Jan. 2021) there was a fascinating editorial titled:
“Between a Rock and a Hard Place: Calcium Supplements, Calcified Atheroma, and Cardiovascular Disease Risk”
Here is the introduction:
“Adequate calcium intake is advised to optimize bone and overall health. The Food and Nutrition Board at the U.S. Institute of Medicine recommends a daily adult intake of 1,000 mg of calcium, which should be increased to 1,200 mg/day in women age ≥50 years and men age ≥70 years. In persons unable to obtain sufficient calcium supply through foods, oral calcium supplementation might be recommended on top of diet.”
The authors go on to note that:
“Several studies have suggested, however, that there might be a non-negligible risk of cardiovascular disease (CVD) events associated with intake of high doses of exogenous calcium through oral supplements.”
The conclusion is that people should try to get their calcium from food. If that is not possible, calcium pills may be warranted under medical supervision:
“Use of the smallest amount of calcium supplement needed (i.e., <500 mg) to complement dietary intake should be prioritized. On the other hand, over-the-counter and off-label use of supplements without the recommendation by clinician advice should be discouraged, at least until more conclusive evidence is available.”
CACS or Coronary Artery Calcium Scoring:
Many cardiologists now scan for calcium in coronary arteries. Although this test is surprisingly controversial, many cardiologists believe it is a reasonable indicator of heart attack risk (Journal of Personalized Medicine, Aug. 20, 2020).
Here’s is what the University of Maryland Medical Center says about its Cardiac Calcium Scoring (Heart Scan):
“The coronary arteries are the vessels that supply oxygen-rich blood to the heart. Plaque — made of fat, calcium and other substances — can build up and narrow or close the arteries.
“Plaque or calcium build-up in the coronary arteries causes heart disease or can lead to a heart attack. The coronary calcium scan is a better predictor of coronary events than cholesterol screening or other risk factor assessments.”
The Harvard Heart Letter (June 2014) adds this:
“Cardiologists constantly seek better ways to predict who will have a heart attack. Among the many potentially helpful options is a coronary artery calcium scan. This test uses a special x-ray machine called a computed tomography (CT) scanner that takes multiple pictures of the heart in thin sections. Combined, the scans produce a view that can reveal specks of calcium in the walls of the heart’s arteries. These specks, called calcifications, are an early sign of cardiovascular disease.”
Calcium Pills and Blood Calcium Levels:
When people take calcium pills, their blood levels of calcium 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.
One might conclude that calcium pills are problematic for the heart. Recent research contradicts that assumption, though. Here is what an epidemiological study published in Clinical Pharmacology and Therapeutics (Feb. 2020) highlights:
“Calcium supplements alone or combined with vitamin D have been reported to increase the risk of acute myocardial infarction (AMI) [heart attack] and, as a consequence, their use in the prevention of osteoporotic fractures has been put into question.
“Is there an increase in the risk of AMI associated to the use of calcium supplements, either alone or combined with vitamin D?”
The study concludes that:
“The results do not confirm the hypothesis that calcium supplements increase the risk of AMI. Instead, calcium supplements containing high‐dose vitamin D appear to reduce the risk of AMI, particularly in patients at high cardiovascular risk.”
The authors admit, however, that they have found an increased risk of stroke associated with a daily dose of 1,000 mg of calcium or higher.
Confused? We would not blame you. Science is messy! The final word is not in about calcium pills and cardiovascular health. One thing we can say with reasonable confidence: eating foods containing calcium should be safe.
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.
One long-term study found that people who get ample calcium from their diets may be protected from cardiovascular disease (Journal of the American Heart Association, Oct. 11, 2016). People who took supplements, on the other hand, were more likely to develop coronary artery calcification.
A recent review concluded (Clinical Interventions in Aging, Nov. 28, 2018):
“…calcium is a double-edged sword, which may be both potentially crucial and perilous.”
Getting the balance just right may be trickier than most people realize.
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).
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 have written about this topic:
Calcium Supplements Do NOT Prevent Broken Bones
Tens of millions of people swallow a calcium pill daily to build strong bones. Are they wasting their money and possibly putting their health in jeopardy
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 causing calcification of soft tissue. 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:
Are Calcium Supplements Bad for Women’s Brains?
A Swedish study shows that women with a history of stroke or cerebrovascular disease are at greater risk for dementia if they take calcium supplements.
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. At that time he was 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 free.
What do you think about this calcium controversy? We are the first to admit that the calcium story is confusing. We would love to read your thoughts in the comment section below.