An analysis of data on nearly 24,000 people followed for over a decade suggests taking calcium supplements may increase the risk of having a heart attack. This is the main finding of a study published online this week in the journal Heart that also concludes boosting overall calcium intake through dietary sources brings no significant benefit in terms of reducing risk of heart disease or stroke.
The researchers say calcium supplements, which are often recommended to the elderly and women after the menopause to protect against bone thinning, should be “taken with caution”. Some experts are saying we should wait for further research to corroborate these findings before acting on this advice, and people who take supplements who are concerned should talk to their doctor.
The findings also appear to go against previous studies that have shown a higher calcium intake is linked to a lower risk of a number of conditions that predispose to heart disease and stoke, namely high blood pressure, obesity, and type 2 diabetes.
The study is based on data collected on participants who were aged 35 to 64 years old between 1994 and 1998 when they joined one of the German arms of the EPIC (European Prospective Investigation into Cancer and Nutrition) study in Heidelberg.
At the start of the study the participants filled in questionnaires that assessed their diet for the previous 12 months, and they also answered questions about regular intake of vitamin and mineral supplements.
Their health was followed for an average of 11 years afterwards. During this time, the group experienced 354 heart attacks and 260 strokes, and 267 participants died of related causes.
When they analyzed the results, the researchers ranked them according to levels of calcium intake, and examined them from various points of view, such as calcium intake including supplements, and the effect of supplements alone. They also adjusted them to remove as far as possible effects from other known influencing factors.
They found participants with a moderate intake of calcium from all sources (820mg a day, including supplements) had a 31% lower risk of heart attack than the ones in the bottom 25% of calcium intake.
But those who calcium intake from all sources, including supplements, was higher than 1,100mg a day did not have a significantly lower risk of heart attack than the bottom intake group.