Calcium pills may up heart attack risk, study suggests
After years of Canadians hearing that they need to consume more calcium, a new study suggests calcium supplements might increase their risk of having a heart attack or stroke.
While calcium's benefits for bone health are well known, there has also been research that has linked higher calcium intake with a lowered risk of high blood pressure, obesity, and type 2 diabetes -- all of which can raise the risk of heart attack and stroke.
But this study suggests that not only is there no heart benefit from a high calcium intake, those who take calcium pills might actually have a higher risk of a heart attack or stroke.
The researchers say their findings are concerning and urge that calcium pills "be taken with caution."
The study appears in the online issue of the journal Heart, and is based on a large study from Germany involving almost 24,000 people who were tracked for more than 10 years.
All the participants, who were middle-aged at the start of the study, filled out food questionnaires and were quizzed about whether they regularly took vitamin and mineral supplements.
During the next 11 years or so, there were 354 heart attacks and 260 strokes among the group, leading to 267 deaths.
When the researchers looked at the diets of the participants, they found that a little bit of calcium was better than almost none, but that there was no heart benefit from boosting calcium levels.
Those who took in a moderate amount of calcium a day from both food and supplements -- about 820 mg daily -- had a 31 per cent lower risk of having a heart attack than those who had the lowest calcium intake.
But those who had a daily intake of more than 1100 mg daily did not have a significantly lower risk of heart attack or stroke.
When the researchers dug further to focus on vitamin and mineral supplements, they found that those who took vitamin and mineral pills were 86 per cent more likely to have a heart attack than those who didn't use any supplements.
The news was even worse for those who used only calcium supplements: they were more than twice as likely to have a heart attack as those who didn't take any supplements.
One of the authors of the study, Sabine Rohrmann, Division of Cancer Epidemiology and Prevention in the Institute of Social and Preventive Medicine at the University of Zurich, says the findings are concerning, given that so many women take calcium pills in a bid to prevent osteoporosis.
She wonders whether calcium pills deposit too much of the mineral into the body at once.
"When you have a high intake of calcium from foods, you have an intake that is distributed over the day. When you take one supplement, you take about 1,000 milligrams right at one moment," she told CTV News.
"We are not sure what is going to happen to the calcium levels in the blood when you have a very high intake just once a day."
Health Canada currently recommends that most adults aim for a total of 1,000 mg of calcium a day. Adults aged 51 and over are advised to aim for 1,200 mg a day.
This latest study adds to the mounting evidence that the heart risks posed by calcium pills might actually outweigh the benefits they offer in reducing bone fractures.
Amid those studies, Health Canada is currently conducting an ongoing review of the benefits and risks of calcium supplements.
It says previous studies have been inconclusive about the link between calcium supplement use and the risk of heart attacks, but it will be reviewing this latest research as well.
Dr. Aliya Khan, a professor of clinical medicine at McMaster University and a member of Osteoporosis Canada's scientific advisory council, says this study adds to concerns that calcium pills may be linked to an increased risk of heart events, whereas calcium from dietary sources appears to be safe.
"Osteoporosis Canada advises that women meet their calcium needs from dietary sources if possible and if this is not possible, then calcium supplements may be used in order to obtain the daily requirement of 1,200 mg of elemental calcium," she told CTV News in an email.
She added that she hoped further well-designed studies will help to shed more light on this issue.
With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip