Eating Chocolate May Decrease Risk of Irregular Heartbeat, Study Shows

BIDMC Contact: Emily Barrett Phone: 617-667-7372; Email:

MAY 23, 2017

Link found between chocolate consumption and lower risk of atrial fibrillation

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  • Chocolate consumption, particularly of dark chocolate, has been linked to improvements in various indicators of heart health.
  • This study examined the possible association between chocolate intake and a lower rate of being diagnosed with atrial fibrillation.
  • While this is an observational study, researchers believe these findings warrant further consideration to identify effective prevention strategies for atrial fibrillation.

BOSTON – A new study led by researchers at Beth Israel Deaconess Medical Center (BIDMC), in collaboration with researchers at the Harvard T.H. Chan School of Public Health and the Aalborg University and Institute of Cancer Epidemiology in Denmark, found that consuming moderate amounts of chocolate was associated with significantly lower risk of being diagnosed with atrial fibrillation (AF), a common and potentially life threatening type of irregular heartbeat. The findings were based on data collected and analyzed from a large study of men and women in Denmark. The study published online today in the journal Heart.

Elizabeth Mostofsky

“Our study adds to the accumulating evidence of the health benefits of moderate chocolate intake and highlights the importance of behavioral factors for potentially lowering the risk of arrhythmias,” said lead author Elizabeth Mostofsky, ScD, MPH, a postdoctoral fellow at BIDMC and an instructor in the Department of Epidemiology at Harvard T. H. Chan School of Public Health.

Previous studies suggest that cocoa and cocoa-containing foods – in particular, dark chocolate, which has a higher cocoa content than milk chocolate – confer cardiovascular benefits, perhaps because of their high content of flavanols, which may promote healthy blood vessel function. But there is only limited research on the association between consuming chocolate and the occurrence of AF, which affects 2.7 to 6.1 million Americans and is linked with higher risk of stroke, heart failure, cognitive decline, dementia, and death.

The study included 55,502 men and women participating in the Danish Diet, Cancer and Heath Study. The researchers obtained information on the study participants’ body mass index, blood pressure and cholesterol, which were measured when participants were recruited between 1993 and 1997. They also looked at participants’ health conditions, including high blood pressure, diabetes, or cardiovascular disease as well as data on their diet and lifestyle gathered from questionnaires. Using a validated questionnaire, the researchers collected information about the participants’ daily chocolate intake.

Among the participants recruited, 3,346 cases of AF occurred over a 13.5 year follow-up period based on data collected from the Danish National Patient Register. Compared with participants who ate a one-ounce serving of chocolate less than once per month, participants who ate one to three servings per month had a 10 percent lower rate of AF; those who ate one serving per week had a 17 percent lower rate; and those who ate between two and six servings per week had a 20 percent lower rate. The benefit leveled off slightly with greater chocolate consumption, with those eating one or more servings per day having a 16 percent lower AF rate on average. Results were similar for men and women.

“Despite the fact that most of the chocolate consumed by the study participants likely had relatively low concentrations of potentially protective ingredients, we still 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,” Mostofsky said. “Eating excessive amounts of chocolate is not recommended, however, 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.”

“This study adds to the growing body of evidence that, compared with other snacks or treats, eating small amounts of dark chocolate on a regular basis as part of an overall balanced, heart-healthy diet is a good option that may reduce the risk of cardiovascular disease,” said study author Murray Mittleman, MD, DrPH, a preventive cardiologist at BIDMC and professor of epidemiology at Harvard T.H. Chan School of Public Health.

In addition to Mostofsky and Mittleman, study authors include Kim Overdad, MD, PhD, Aalborg University Hospital and Western University; Martin Berg Johansen, MSc, Aalborg University Hospital; Anne Tjønneland, MD, PhD, DMSc, Institute of Cancer Epidemiology; and Harpreet S. Chahal, BMSc, Western University.

Funding for the study came from grants from the National Heart, Lung, and Blood Institute (HL-115623), the European Research Council (ERC), EU 7th Research Framework Program (281760), a KL2/Catalyst Medical Research Investigator Training award (an appointed KL2 award) from Harvard Catalyst | The Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health Award KL2 TR001100) and the Danish Cancer Society and the Danish Council for Strategic Research (Aalborg AF-Study Group).

About Beth Israel Deaconess Medical Center

Beth Israel Deaconess Medical Center is a patient care, teaching and research affiliate of Harvard Medical School and consistently ranks as a national leader among independent hospitals in National Institutes of Health funding.

BIDMC is in the community with Beth Israel Deaconess Hospital-Milton, Beth Israel Deaconess Hospital-Needham, Beth Israel Deaconess Hospital-Plymouth, Anna Jaques Hospital, Cambridge Health Alliance, Lawrence General Hospital, MetroWest Medical Center, Signature Healthcare, Beth Israel Deaconess HealthCare, Community Care Alliance and Atrius Health. BIDMC is also clinically affiliated with the Joslin Diabetes Center and Hebrew Rehabilitation Center and is a research partner of Dana-Farber/Harvard Cancer Center and the Jackson Laboratory. BIDMC is the official hospital of the Boston Red Sox. For more information, visit