Calcium supplements that many women take to boost bone health increase their risk for heart disease, a new study by researchers at Johns Hopkins Medicine and other institutions has found.
At the outset of the study, the participants completed in-depth questionnaires about their diet (specifically looking for calcium-rich foods like cereals, dairy products and leafy greens) as well as what supplements and drugs they took daily.
Heart scans were also taken before and after the study period, to examine plaque in the arteries.
After adjusting for other risk factors, the researchers found those with the highest calcium intake (above 1400 milligrams a day) were about 30 per cent less likely to develop heart disease than those with the lowest intake (below 400mg).
But, when they broke down the data amongst the high-intake group and split them based on whether their calcium was consumed in the form of supplements or whole foods, they found the supplement group had a 22 per cent higher likelihood of developing heart disease.
“There is clearly something different in how the body uses and responds to supplements versus intake through diet that makes it riskier,” co-author John Anderson, a professor emeritus of nutrition at the University of North Carolina, said. “It could be that supplements contain calcium salts, or it could be from taking a large dose all at once that the body is unable to process.”
While the researchers stressed their findings do not prove cause and effect, they do add to concern about supplement use.
Kamal Patal, a nutrition researcher and the director of independent supplement analysis site examine.com, is not surprised by the findings.
“This is something I’ve suspected since 2009, when we put out a systematic review on calcium and vitamin D,” Patal says.
“In a nutshell, calcium supplements make it more likely to experience elevated blood calcium levels, compared to food that has calcium in lower doses and different forms.
“In fact, a paper just came out showing for the first time that vitamin D supplements could really increase the risk of hypercalcemia. So imagine all those unsuspecting people taking a combined vitamin D and calcium supplement each day.”
He adds that not all calcium supplementation is “bad”.
“It’s just that other nutrients like vitamin K2 play an important role in getting calcium to places where it’s helpful (like bone) and away from arteries.”