Cocoa Flavanols: Emerging Research Is Taking Us Deeper Inside the Cacao Bean

Apr 15, 2016

  • Consumer media have, for the past couple of years, been hailing chocolate (particularly dark chocolate) as offering such health benefits as lowered body-mass index and improved mood. Unfortunately for chocolate lovers everywhere, these claims for chocolate itself have not yet been sufficiently borne out by scientific research. What is coming to light, however, are some of the effects cocoa flavanols, bioactive compounds naturally present in the cacao bean, have on the human body.

    The amount of flavanols in a cocoa-based product depends on various factors, including plant genetics, the method used for harvesting it, how the cocoa itself is processed, and how the final product is prepared. The effects of cocoa flavanols on human health may include improved vascular function and cholesterol levels in the general population, improved blood-vessel function in patients with kidney failure, and improved memory and cognition.

    It is important to keep in mind, however, that the studies to date on these effects of cocoa flavanols have been small, and further evidence is needed to support them, in the form of large-scale randomized trials. To this end, the Cocoa Supplement and Multivitamin Outcomes Study (COSMOS), based at Harvard University-affiliated Brigham and Women’s Hospital and in collaboration with Mars Inc., is enrolling 18,000 participants and is the first large-scale, long-term randomized trial examining cocoa flavanols’ benefits. For this study, women 65 or older and men 60 or older will be randomly assigned to consume either 750 mg of cocoa flavanols per day in capsule form or an identical capsule containing a placebo. The researchers will follow the participants for four years and compare the numbers of heart attacks, strokes, and deaths in each group. Ancillary studies will be centered on potential benefits of cocoa flavanols on brain health, including memory, decision-making skills, mood, and cognitive performance, and on metabolic health.

    JoAnn Manson, MD, chief of the Division of Preventive Medicine at BWH and co-leader of the COSMOS study, stated in press statements about COSMOS that the trial “builds on a decade of scientific evidence indicating that cocoa flavanols improve blood-vessel function, metabolic health, and cognition. The depth and breadth of this innovative trial are unprecedented.”

    The following three slides summarize three of the more promising potential benefits cocoa flavanols may offer.


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  • Cardiovascular Benefits

    Most studies on cocoa flavanols’ effects on cardiovascular health indicate that the flavanols can improve vascular function and blood pressure, and raise HDL (“good”) cholesterol levels. For example, studies published recently in Age and British Journal of Nutrition demonstrated that consuming cocoa flavanols significantly improved vasodilation in both young and older men (Age) and improved blood-cholesterol profile, blood pressure, and vasodilation in healthy men and women (British Journal of Nutrition).

    Results from the COSMOS trial, expected in 2019, will likely shed additional light on cocoa flavanols’ benefits on cardiovascular health.

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  • Improved Blood-Vessel Function in Kidney-Dysfunction Patients

    The American Society of Nephrology reported in December of last year the results of a study investigating the effects of cocoa flavanols on patients with kidney failure. The study, led by Tienush Rassaf, MD, of University Hospital Essen (Germany), found that consuming a beverage containing cocoa flavanols improves blood-vessel function in patients with kidney failure.

    Rassaf’s team randomized 57 dialysis patients to drink either a cocoa-flavanol-rich beverage or a control beverage free of flavanols (but that otherwise matched the nutrient profile of the test beverage) every day for 30 days. After those 30 days, the investigators found that the cocoa flavanols were tolerated well by patients and improved their blood-vessel function and reduced diastolic blood pressure.

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  • Memory and Other Cognitive Improvements

    Cocoa flavanols may improve memory and offer additional cognitive benefits. Results of a study published in the journal Nature Neuroscience just over a year ago suggest that consuming cocoa flavanols reverses age-related memory decline in healthy older adults. A press release issued by Columbia University Medical Center (New York City), where the research originated, stated that this study “provides the first direct evidence that one component of age-related memory decline in humans is caused by changes in a specific region of the brain [the dentate gyrus] and that this form of memory decline can be improved by a dietary intervention.”

    When research subjects’ brains were imaged, the research team found “noticeable improvements in the function of the dentate gyrus in those who consumed the high-cocoa-flavanol drink,” lead author Adam M. Brickman, PhD, is quoted as saying in the press release. This group performed better on memory tests.

    Senior author Scott A. Small added that the team’s findings will need to be replicated in a larger study.

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