People who love to eat chocolate appear to have lower rates of heart problems, a large review has found. But doctors remain puzzled about whether it's really the chocolate itself that's helping the heart.

Chocolate has been linked to heart health in a number of studies already. These findings come from a meta-analysis that focused on seven already published studies. Researchers from the United Kingdom and Colombia reviewed the seven studies, all of which examined the link between eating chocolate and heart disease.

In all, 114,000 participants were involved in the studies and each was asked to record how much chocolate they took in, whether through candy, cookies, hot cocoa or other forms.

Among the seven studies, five showed a link between higher levels of chocolate consumption and a lowered risk of cardiovascular problems. Two did not.

When all the data was examined together, the researchers found that the highest levels of chocolate consumption were associated with a 37 per cent reduction in cardiovascular disease, and a 29 per cent reduction in stroke, compared with the lowest levels.

None of the studies, including the meta-analysis, were funded by chocolate companies or related industries. The research was presented at the European Society of Cardiology Congress and appears in

The review authors note that there were some problems with all the studies they looked at. While the studies did try to control for factors that might raise the risk of heart problems, such as age, body mass index, physical activity, smoking and other aspects of diet, they did not differentiate between those who ate dark and milk chocolate.

One of the components of chocolate often touted for its positive health effects are chocolate's polyphenols, which are found in higher levels in dark chocolate than milk chocolate. Polyphenols are antioxidants that appear to improve "endothelial function," an element of the blood system that affects the risk of stroke and heart attack. Polyphenols might also have a positive effect on blood pressure and insulin resistance.

The researchers say more research is needed to test whether it was the chocolate itself that actually caused the better heart health outcomes or if there was another confounding factor that they didn't account for. Perhaps, for example, the act of eating the treat relaxes the heart and lowers blood pressure.

The authors also noted that while chocolate might offer some heart benefits, it also brings with it a lot of fat and calories that could outweigh any of its benefits.

"The high sugar and fat content of commercially available chocolate should be considered, and initiatives to reduce it might permit an improved exposure to the beneficial effect of chocolate," the research team wrote.