The statement that chocolate is good for health is attributed to the cocoa in chocolate. Cocoa flavanols are natural antioxidants. Some studies have indeed shown that cocoa flavanols can help reduce the risk factors that can lead to cardiovascular disease in the short term, mainly by controlling blood pressure and vasodilation. 

    However, the existing research evidence are mostly relied on small research and the proven effect are all short-term improvement, which can not explain that cocoa flavanol has the long-term effect of improving cardiovascular health.

    In order to further find evidence, researchers from research institutions such as Brigham and Women's Hospital Affiliated to Harvard Medical School conducted a large-scale randomized controlled trial from 2015 to the end of 2020, which tested whether cocoa extract supplement has long-term effect on preventing cardiovascular disease for the first time. Recently, the results of this trial were published in the American Journal of Clinical Nutrition.

    More than 21,000 people over the age of 60 participated in this large trial and were randomly assigned to take cocoa extract supplements, multivitamins, or placebo separately. According to the news of the Research Institute, this is the largest clinical dietary intervention trial to study the effects of cocoa flavanol and multivitamins on cardiovascular health and cancer.

    The researchers pointed out that in the trial they use cocoa extract supplement rich in flavanol instead of chocolate itself is to ensure that people eat a certain level of cocoa flavanol and avoid excessive sugar and fat with chocolate.

    In this trial, the researchers focused on the clinical cardiovascular events of participants, with the total cardiovascular events as the main outcome index. During a median follow-up of 3.6 years, 410 participants taking cocoa extract and 456 participants taking placebo confirmed cardiovascular events, including myocardial infarction, stroke, cardiovascular death, coronary revascularization, carotid artery disease, peripheral artery surgery, unstable angina pectoris, etc.

    This result showed that cocoa flavanol intervention reduced total cardiovascular events by 10% compared with placebo, but the difference was not statistically significant.

    The study also reported key secondary outcome indicators. The results showed that those who received cocoa flavanol supplementation have lower cardiovascular mortality rate by 27% than that in the placebo group.

    Based on all the evidence for the primary and secondary cardiovascular endpoints of the trial, we see promising signals that cocoa flavanol supplements can reduce important cardiovascular events, including cardiovascular death. Dr. Howard Sesso, one of the study leaders, concluded, “These findings deserve further research to better understand the impact of cocoa flavanol on cardiovascular health. "

    In addition, the researchers also pointed out in the analysis that among participants with good compliance, that is, those who keep taking supplements regularly, the effect of cocoa flavanol supplementation is more obvious, reducing total cardiovascular events by 15% and cardiovascular mortality by 39%.

    "Although our study proves that cocoa flavanol shows good signals of cardiovascular protection, any health benefits of taking these supplements need to be verified in future trials," said Dr.JoAnn Manson, another study leader.

    It is worth mentioning that like many similar studies, this trial has its stakeholders. The paper states that Mars provided sponsorship and research for the study, and the cocoa flavanol supplement taken by participants was donated by Mars Edge, a subsidiary of Mars.

    In addition to the prevention of cardiovascular disease, this large-scale trial also tested whether cocoa flavanol supplement can help prevent cancer. However, in view of the relatively short follow-up time and other factors, sufficient data have not been obtained.

    Dr Sesso added: "what we can now tell consumers is to maintain a healthy and balanced diet, eat more natural foods rich in flavanols, and continue to pay attention to the important results of this experiment for health."