Researchers from Brown as well as Brigham and Women’s Hospital found small but significant links between cocoa consumption and cardiovascular health benefits.
The study, led by Xiaochen Lin GS with contributions from Simin Liu, professor of epidemiology, assessed the health benefits of cocoa consumption through a systematic review and meta-analysis of 19 randomized studies.
The researchers focused on the effects of a particular compound in cocoa called flavanol. “There have been quite a few studies implicating cocoa as a beneficial nutritional strategy to improve cardiometabolic health, and we and others have done work indicating that cocoa flavanol may be the active compound responsible for the beneficial effects,” Liu and Lin wrote in an email to The Herald.
“Flavanols are rich in certain food items, such as cocoa, green tea and colored berries,” they wrote. In one 37-gram bar of dark chocolate there can be around 800 milligrams of flavanols. The meta-analysis found beneficial effects from consuming 200 to 600 mg of cocoa flavanols per day.
The meta-analysis looked at data from a combined 1,139 participants, who completed studies of different sizes and durations. “By combining these studies together in this meta-analysis, it enables us to look with a little more clarity at the overall effect by essentially combining all of the data from the trials together,” said Howard Sesso, an associate professor at Harvard Medical School and an associate epidemiologist at Brigham and Women’s Hospital who collaborated on the analysis.
“There were small-to-modest but statistically significant improvements among those who ate flavanol-rich cocoa product (versus) those who did not,” Liu and Lin wrote.
“For biomarkers for lipids, metabolism and insulin we found significant improvements,” Sesso said.
Though these findings were “very significant” in that they were the first to “synthesize the potential mechanisms by which cocoa flavanols may affect cardiometabolic health,” Liu and Lin also noted the limitations of their study. “Through this research, we also identify the additional gaps in the current knowledge and potential target for future investigations,” they wrote.
Whether consuming cocoa flavanols “really translates to hard clinical outcomes” is “still an open question,” Sesso said.
“It really is time to have a large long-term (randomized controlled test)” to more concretely assess the health effects of cocoa flavanols, Liu and Lin wrote. They pointed to the Cocoa Supplement and Multivitamin Outcomes Study, a large clinical trial that will extend over the next four years currently led by Sesso and JoAnn Manson, a Harvard Medical School professor, chief of preventative medicine at Brigham and Women’s hospital and contributor to the cocoa flavanols meta-analysis.
Though researchers from Brown received no outside funding, Manson and Sesso reported receiving funding from Mars Symbioscience, a research arm of the chocolate company Mars, Inc. formed in 2005, for their COSMOS trial. The literature around cocoa flavanols has been “building for about a decade,” Sesso said.
Sesso acknowledged the possible difficulties in separating science from marketing. People often conflate cocoa or cocoa flavanols with chocolate — a “wrong comparison,” Sesso said, because “chocolate has calories — sugars and fat calories.” Nonetheless, this comparison has prompted a glut of recent news articles that used the Brown study as proof that chocolate is healthy. “Rejoice! Chocolate is good for your heart, scientists declare in ‘clearest evidence to date,’” read one Daily Mail headline.
While Sesso and Liu recognized that there is much more work to be done in this field before strong conclusions can be reached, the Mars Symbioscience webpage touts cocoa flavanols as “scientifically proven to promote a healthy heart by supporting healthy blood flow.”
The influence that Mars, Inc. has on cocoa research has subsequently come under fire. “A lot of the science on flavanols has been done by the Mars Center for Cocoa (Health) Science in collaboration with other researchers because commercial interests have a high stake in whether these compounds really do have health benefits,” an article in Business Insider stated.
For the media to point to a potential conflict of interest regarding a chocolate bar company’s involvement in research on the health benefits of cocoa compounds is “a totally fair comment,” Sesso said. “But the scientific part of the paper, of the trial, is completely investigator-initiated — it’s independent of the sponsor.”
While the meta-analysis did find promising evidence for the benefits of cocoa flavanols, “the findings from the current study ought not be simply generalized to different sorts of chocolate candies,” Liu and Lin wrote. Cocoa powder has a more reliable flavanol content than candies, Sesso said.
