Until recently, extra calcium was considered essential for good health. Millions of women popped a calcium pill or two every day. They assumed there were no calcium side effects, though some complained that calcium carbonate was constipating. Now a new study suggests that too much calcium just might do the body harm.

Nutritionists Embraced Calcium Supplements:

Many health professionals are skeptical about the value of supplements. They often advise their patients to eat a well-balanced diet and skip vitamin and mineral pills.

The exception has been calcium, sometimes with vitamin D. For decades, doctors have advised women (and some men) to take calcium supplements to ward off osteoporosis and bone fractures.

It seemed so logical. The National Institutes of Health (NIH) Osteoporosis and Related Bone Diseases National Resource Center states unequivocally:

“Inadequate calcium significantly contributes to the development of osteoporosis. Many published studies show that low calcium intake throughout life is associated with low bone mass and high fracture rates. National nutrition surveys have shown that most people are not getting the calcium they need to grow and maintain healthy bones.”

The experts recommend that women aged 51 to 70 should be taking in 1,200 mg of calcium daily. Men are told that they need 1,000 mg of calcium each day. To achieve such goals many people need calcium supplements.

Calcium Against Colorectal Cancer?

There was even some preliminary data suggesting that extra calcium might reduce the risk of colorectal cancers (Cochrane Database of Systematic Reviews, Jan. 23, 2008).

How Good is Extra Calcium?

After further study, however, the idea that calcium could prevent either osteoporosis or colon cancer has not held up. A recent meta-analysis published in JAMA did not find evidence that calcium supplements reduce the risk of hip fractures (JAMA, Dec. 26, 2017). This was a large review. It involved 33 randomized clinical trials and over 50,000 participants. The heretical conclusion:

“In this meta-analysis of randomized clinical trials, the use of supplements that included calcium, vitamin D, or both compared with placebo or no treatment was not associated with a lower risk of fractures among community-dwelling older adults. These findings do not support the routine use of these supplements in community-dwelling older people.”

Now, the notion that calcium protects against colon polyps has also been upended. A gold-standard, randomized controlled trial of more than 2000 people has just been published (Gut, March 1, 2018).

Unexpected Calcium Side Effects:

This study included more than 2,000 middle-aged Americans at high risk of polyps because they had already had one or more discovered during a colonoscopy. These volunteers were randomly assigned to take 1200 mg of calcium, 1000 IU of vitamin D3, both or neither for at least three years. Then they had another colonoscopy to look for polyps. At that point, the scientists saw no effect.

The investigators also collected data on polyps found after the treatment had stopped. That is when they discovered that the supplements increased the likelihood of precancerous polyps. Calcium alone raised the risk 2.65 times, while calcium with vitamin D made people 3.8 times more likely to develop polyps six to eight years after starting supplementation.

The authors of the study point out that both women and smokers were at higher risk of polyps when they took supplemental calcium. As a result, doctors might want to change their advice.

It no longer seems prudent to urge all women to take extra calcium and vitamin D “just in case.” Those who have already had a polyp and those who smoke may need to be particularly cautious about taking such supplements.

Calcium Side Effects and the Heart

In addition to the colorectal polyp controversy, there has been great uncertainty about whether calcium pills are safe for the heart and arteries. The Nurses’ Health Study, with 74,245 women observed over 24 years did not find any risk (Osteoporosis International, Aug. 2014).

Data from the Women’s Health Initiative, however, indicate a modest cardiovascular risk associated with calcium supplements with or without vitamin D (BMJ, April 19, 2011).

A prior analysis in BMJ (July 29, 2010) of 15 trials and more than 8,000 participants concluded:

“Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction [heart attack]. As calcium supplements are widely used these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population. A reassessment of the role of calcium supplements in the management of osteoporosis is warranted.”

People’s Pharmacy Perspective:

Calcium side effects such as constipation are not considered worrisome. But our readers beg to differ. One shared this story:

“I know the desperation some of your readers feel about constipation because I suffered the same problem for years. Those who haven’t experienced this problem have no idea of its severity.

“I tried increasing fiber and fluids to no avail. I became convinced that the constipation was related to my medication. Over a period of time, by the process of trial and error, I narrowed it down to a calcium supplement I had been taking for years.

“I haven’t taken any calcium since then, and I haven’t had the problem either. I hope this information will help someone else.”

E.N. shared a similar story:

“Had the same problem. I was taking Tums for the calcium for about 2 years. I also took magnesium daily along with cooked greens and apples and bran type cereal daily. Made no difference. The calcium overcame all that and I came very close to having an impacted bowel. I stopped the Tums….have not had the problem since.”

More Serious Calcium Side Effects:

Now that we have data about calcium supplementation and colon polyps and vascular complications, we may want to rethink the reflex recommendation that everyone over 51 should be taking a calcium supplement.

Perhaps calcium supplements are not a great back-up plan to make up for inadequate dietary intake. Instead, people may need to concentrate on getting calcium from their food choices. So far no one has linked constipation, polyps or heart attacks to foods containing calcium.

What Foods are High in Calcium?

While everyone knows that milk is a good source of calcium, many older people don’t drink milk. They might consider yogurt, mozzarella or Cheddar cheese, or they might turn to tofu, turnip greens, collards, kale or bok choy.

Canned salmon or sardines, with the bones, are also good food sources of calcium and provide some vitamin D as well. Soybeans, white beans, sesame seeds and almonds can also help supply dietary calcium.

With careful attention to menu planning, people can be confident they are getting the calcium they need. They won’t have to run even modest risks of colon polyps or calcified plaque from taking calcium pills.

Want to learn more about other ways to prevent osteoporosis and fractures? Our radio show # 752 titled Bone Vitality is free. It features Walter Willett, MD, DrPH, one of the world’s foremost nutrition experts and epidemiologists. He is at Harvard’s School of Public Health. The MP3 download is FREE! Do not be confused by the $9.99 price for the CD. Where it says Choose CD or MP3 Version click on the downward arrow to select the FREE MP3 version. The price turns to $0.00 instantly.

Another freebie that is worth listening to is more recent. Show # 1093 is titled “How to Keep your Bones Strong.” It too is free. You can stream the audio by just clicking on the green arrow at in the black box at the top of the page or select the free MP3 version at the bottom of this page.

Related People's Pharmacy Radio Show

Watch a brief welcome from Joe & Terry

Your browser doesn't support HTML5 video.