A high intake of flavonoid-rich foods, primarily fruits and vegetables, was linked to significant reductions in incident diabetes risk, a large-scale observational study published in the Journal of Nutrition concluded.
 
Flavonoids, a wide-ranging class of polyphenols, have been linked to a host of health benefits tied to metabolism, including cardiovascular disease, obesity, hypertension, and more, with some meta-analyses published showing a significant relationship between habitual flavonoid intakes and reduced diabetes risk. The present study sought to further examine this relationship while also differentiating the flavonoid types across three subclasses – flavonols, flavanols, and anthocyanins, which appear in various concentrations across different food sources.
 
The authors of the study relied upon the health outcomes of 54,787 participants of the Danish Diet, Cancer, and Health study, associating total flavonoid and flavonoid subclass intakes with body fat, incident diabetes, and secondary outcomes, such as the potential mediating effect that body fat content or smoking status could have in order to determine which sub-populations might benefit the most from higher flavonoid intakes. Flavonoid intakes were measured via food frequency questionnaires which aimed to cover a range of flavonoid sources.
 
Throughout the study, 6,700 individuals were diagnosed with diabetes, over a median-follow-up period of 20.8 years. The study found that while overall flavonoid intake was inversely associated with diabetes risk, the beneficial relationship appeared to plateau at moderate flavonoid intake, and was not modified by smoking status, BMI, physical activity level, or sex.
 
However, those who are at a higher risk of diabetes, namely those with obesity, seemed to benefit the most from a higher flavonoid consumption. Out of the six total subclasses of dietary flavonoids, four (flavonols, flavonol monomers, flavanol oligo + polymers, and anthocyanins) were associated with a lower risk of diabetes when consumed with moderate-to-high intakes.
 
The authors concluded, based on the present study and the overall outcomes of cohorts in the original Danish study, that diets “high in fruits and vegetables, whole grains, nuts, and legumes, low in both red and processed meats, sugar-sweetened beverages, and refined grains, and with a moderate alcohol intake” were optimal for the prevention and management of type 2 diabetes.
 
While no mechanisms of action can be established in observational studies, the authors mentioned several areas of activity researchers have proposed could be the reason for this benefit. “A meta-analysis of randomized controlled trials concluded that green tea consumption significantly reduces fasting glucose and hemoglobin A1C concentrations, whereas flavonoid-rich chocolate or cocoa consumption significantly reduces insulin resistance and fasting insulin. However, their exact mechanisms remain to be elucidated.”