Regular chocolate consumption may be linked to a lower risk of developing the heart rhythm irregularity atrial fibrillation, shows research* published online in the journal Heart.
The associations seemed to be strongest for one weekly serving for women and between two and six weekly servings for men.
Given that regular chocolate consumption, particularly of dark chocolate, has been linked to improvements in various indicators of heart health, the researchers wanted to see if it might also be associated with a lower rate of atrial fibrillation.
The study involved 55,502 (26,400 men and 29,100 women) participants, aged between 50 and 64, from the population-based Danish Diet, Cancer and Health Study. Participants provided information on their usual weekly chocolate consumption, with one serving classified as 1 ounce (30 g). But they were not asked to specify which type of chocolate they ate. Most chocolate eaten in Denmark, however, is milk chocolate (minimum 30% cocoa solids).
Information on heart disease risk factors, diet, and lifestyle—roughly one in three smoked—was obtained when the participants were recruited to the study. Their health was then tracked using national registry data on episodes of hospital treatment and deaths.
Those at the higher end of chocolate consumption tended to consume more daily calories, with a higher proportion of these coming from chocolate, and to be more highly educated than those at the lower end of the scale.
During the monitoring period, which averaged 13.5 years, 3,346 new cases of atrial fibrillation were diagnosed. After accounting for other factors related to heart disease, the newly diagnosed atrial fibrillation rate was 10% lower for 1-3 servings of chocolate a month than it was for less than one serving a month.
This difference was also apparent at other levels of consumption: 17% lower for one weekly serving; 20% lower for 2-6 weekly servings; and 14% lower for one or more daily servings.
When the data were analysed by sex, the incidence of atrial fibrillation was lower among women than among men irrespective of intake, but the associations between higher chocolate intake and lower risk of heart flutter remained even after accounting for potentially influential factors.
The strongest association for women seemed to be one weekly serving of chocolate (21% lower risk), while for men, it was 2-6 weekly servings (23% lower risk).
The researchers said: “Despite the fact that most of the chocolate consumed in our sample probably contained relatively low concentrations of the potentially protective ingredients, we still observed a robust statistically significant association.”
However, a linked editorial** sounds a note of caution. Doctors from the Duke Center for Atrial Fibrillation in North Carolina, USA, highlight that the chocolate eaters in the study were healthier and more highly educated—factors associated with better general health—which might have influenced the findings. The researchers were also not able to take account of other risk factors for atrial fibrillation, such as kidney disease and sleep apnoea, and the study included only diagnosed cases of atrial fibrillation, making it difficult to determine if chocolate is associated with a lower risk of atrial fibrillation or only with obvious symptoms.
Dr Tim Chico, reader in cardiovascular medicine and consultant cardiologist, University of Sheffield, said: “Some studies have suggested eating chocolate may have benefits for the heart, but when a health story seems too good to be true, it sadly usually is.”
He added: “They show a benefit of eating chocolate once a month or more, compared with people who eat chocolate less often than this, so the benefit is seen with very infrequent chocolate intake, with little or no benefit of eating it more often. In addition, in this study the people eating more chocolate were actually thinner and healthier overall, both of which reduce the risk of atrial fibrillation. I suspect that the reduced risk of atrial fibrillation is more to do with these factors than their chocolate intake directly.”
* Mostofsky E, Berg Johansen M, Tjønneland A, et al Chocolate intake and risk of clinically apparent atrial fibrillation: the Danish Diet, Cancer, and Health Study. Heart, published online first: 23 May 2017. doi: 10.1136/heartjnl-2016-310357
** Pokorney SD, Piccini JP Chocolate and prevention of atrial fibrillation: what is bad for the pancreas might be good for the atria? Heart, published online first: 23 May 2017. doi: 10.1136/heartjnl-2016-311026