Calcium Not as Great for Bones as Once Thought

A woman pours calcium supplement pills into her hand — (Image credit: Africa Studio/Shutterstock.com)

Calcium has long been touted as a bone-boosting mineral, but the latest evidence confims that consuming more of it may not have the effects experts once thought, according to two new reports from New Zealand.

The reports, both published today (Sept. 29) in the journal BMJ, looked at the effects of calcium intake on bone density and risk of fracture in adults over age 50.

In the first report, researchers analyzed the results of 59 previous randomized controlled trials of calcium involving more than 12,000 people. The investigators found that increasing calcium intake — either through diet or by taking supplements — increased people's bone-mineral density by up to 2 percent. However, the researchers concluded that this increase was not enough to meaningfully reduce a person's risk of fracture. [9 Healthy Habits You Can Do in 1 Minute (Or Less)]

In the second analysis, researchers looked at more than 40 studies of people's diets, and found no link between the amount of calcium people consumed and their risk of fracture. Consuming more calcium appeared to neither increase nor decrease fracture risk. The researchers also looked at 26 randomized controlled trials of calcium supplements, and although the scientists observed a slight reduction in people's fracture risk with calcium supplements, the researchers cautioned that the evidence was "weak and inconsistent."

These are not the first studies to suggest that consuming extra calcium may not improve bone health.

A 2013 report from the U.S. Preventive Services Task Force demonstrated no evidence that taking the mineral along with vitamin D reduced the risk of fracture in healthy, postmenopausal women. (Vitamin D helps your body absorb calcium.)

And getting too much calcium can have adverse effects, including kidney stones.

In addition, in 2011, the Institute of Medicine released a report stating that most Americans get enough calcium in their diets, although the researchers did note that some elderly people do not get enough of the mineral.

Twenty-five years ago, there was a study published "that concluded that calcium supplements to prevent fractures were not justified by the available evidence," Karl Michaëlsson, a professor of medical epidemiology at Uppsala University in Sweden, wrote in an editorial accompanying the two new studies in the journal. That conclusion still holds true, given the findings of these two new studies, he said.

Michaëlsson noted that the previous evidence on dietary calcium had come mostly from observational studies, and these were too different from one another for researchers to put them together in a meta-analysis. However, the new studies also "found little evidence to support the theory that higher intake of dietary calcium could reduce risk of fractures," Michaëlsson wrote.

While future studies could focus on the effects of calcium intake in people with different levels of vitamin D, the currently available evidence "gives us a strong signal that calcium supplements with or without vitamin D do not protect older people in general from fractures," Michaëlsson wrote.

"The weight of evidence against such mass medication of older people is now compelling, and it is surely time to reconsider these controversial recommendations," Michaëlsson wrote.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Sara is a staff writer for Live Science, covering health. She grew up outside of Philadelphia and studied biology at Hamilton College in upstate New York. When she's not writing, she can be found at the library, checking out a big stack of books.