In a collaboration that includes researchers from Aalborg University Hospital in Denmark, the findings highlight the higher flavanol content of dark chocolate, which has shown efficacy in healthy blood vessel function.
In addition, moderate intake was stressed, with overconsumption not recommended in lowering the risk of atrial fibrillation (AF).
“We observed a significant association between eating chocolate and a lower risk of AF--suggesting that even small amounts of cocoa consumption can have a positive health impact," said Elizabeth Mostofsky, instructor in the Department of Epidemiology at Harvard Chan School and lead author of the study.
"Eating excessive amounts of chocolate is not recommended because many chocolate products are high in calories from sugar and fat and could lead to weight gain and other metabolic problems. But moderate intake of chocolate with high cocoa content may be a healthy choice."
Much research has been carried out showing that moderate consumption of chocolate improves markers of cardiovascular health.
Its consumption is linked to a lower rate of heart failure and heart attacks although limited research is available on chocolate’s effect on AF, a common condition affecting 8.8 million in the European Union that is linked to a higher risk of stroke, heart failure, cognitive decline, dementia and mortality.
Heart flutter findings
The present study used data obtained from the Danish Diet, Cancer, and Health Study that enrolled 55 502 participants (26 400 men and 29 102 women) aged 50–64 years.
These subjects provided information on diet and lifestyle via self-administered food frequency questionnaires (FFQ).
Average intake of food items such as chocolate during the last 12 months was reported in 10 categories from ‘never’ to ‘Four to five per day’.
The questionnaire did not differentiate between milk and dark chocolate, but most chocolate consumed in Denmark has a minimum of 30% cocoa solids.
Over a 13.5-year follow-up period, there were 3,346 cases of AF recorded among the study participants.
Men and women who ate one to three servings per month had a 10% lower rate of AF compared to those who ate a one-ounce serving of chocolate less than once per month
Those who ate one serving per week had a 17% lower rate; and those who ate two to six servings per week had a 20% lower rate.
The benefit evened out slightly with greater amounts of chocolate consumption, with those eating one or more servings per day having a 16% lower AF rate. Results were similar for men and women.
“Participants with higher levels of chocolate intake had a lower rate of clinically apparent incident AF or flutter,” the study said
“Future research is necessary to confirm this finding and to determine whether high levels of chocolate intake are associated with higher AF risk.”
Along with the antioxidant, anti-inflammatory and antiplatelet properties of cocoa, the researchers also pointed towards the hypotensive and antiarrhythmic effects of magnesium contained in a typical 100 calorie serving of dark chocolate.
Expert reaction were critical of the study and of its findings. Dr Gavin Sandercock, reader in Clinical Physiology (Cardiology) and Director of Research in Sport & Exercise Science at the University of Essex, commented that AF was not a particularly serious problem.
“AF is often benign so it’s strange to focus just on chocolate and its ‘benefits’ to AF, especially in a study designed to look at cancer risk, like this one.”
“In short, the study shows that people who eat chocolate 1-6 times per week – which is nearly everyone in the study – do have a slightly lower chance of atrial fibrillation, but only if you compare them with a small group of rather unhealthy individuals who don’t (or can’t) eat chocolate more regularly.
Dr Tim Chico, Reader in Cardiovascular Medicine & consultant cardiologist, University of Sheffield, added that when a health story seems too good to be true, it sadly usually is.
“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.”
Published online ahead of print: doi.org/10.1136/heartjnl-2016-310357
“Chocolate intake and risk of clinically apparent atrial fibrillation: the Danish Diet, Cancer, and Health Study.”
Authors: Elizabeth Mostofsky, Martin Berg Johansen, Anne Tjønneland, Harpreet S Chahal, Murray A Mittleman, Kim Overvad