Efficacy of flavan-3-ols on cardiometabolic health: An umbrella review of systematic reviews and meta-analyses of randomized controlled trials and observational studies

Non-communicable diseases (NCDs) remain the leading global health burden; according to the World Health Organization (WHO), seven out of the ten leading causes of death globally in 2021. Today, ischemic heart disease ranks first, and type 2 diabetes mellitus (the most common form of diabetes) is estimated to affect around 4.2 billion people worldwide. The pharmacological treatments for these chronic diseases are on the rise, often presenting clinical side effects and financial burdens on patients, highlighting the need for effective and accessible preventive strategies. A mounting body of evidence suggests flavan-3-ols, a bioactive subclass of flavonoids within the polyphenol family, have potential in reducing the risk of type 2 diabetes, cardiovascular mortality, coronary heart disease, and stroke. Therefore, this umbrella review will systematically assess the credibility and certainty of associations between flavan-3-ols consumption and cardiometabolic health outcomes in adults by synthesizing the evidence from systematic reviews and meta-analyses of randomized controlled trials and observational studies.