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Research published in the journal Nutrition and diabetes Eating more foods rich in flavonoids may help reduce the risk of developing type 2 diabetes.
Type 2 diabetes has become a major public health concern due to a steady increase in prevalence worldwide. Currently, 415 million people worldwide have diabetes, and more than 4 million deaths are related to the disease.
Certain modifiable risk factors, such as obesity and being overweight, are associated with the development of type 2 diabetes, which in turn increases the risk of developing several health complications, including cardiovascular disease, kidney disease, dementia, and certain types of cancer.
A diet high in plant-based foods is known to reduce the risk of type 2 diabetes. Plants are rich sources of a variety of polyphenolic compounds that differ in bioavailability and bioactivity. Flavonoids are a class of polyphenolic compounds that are divided into six major subclasses: flavanones, flavones, flavan-3-ols, flavonols, anthocyanins, and isoflavones.
Evidence from randomized controlled trials (RCTs) shows that higher intakes of flavonoids increase insulin sensitivity, reduce insulin resistance, and improve blood lipid profiles.
In the study, scientists investigated the association between a flavonoid-rich diet and the development of type 2 diabetes in a large UK population.
A total of 113,097 UK Biobank participants were enrolled in the study. The UK Biobank is a large population-based prospective cohort study of over 500,000 adult participants recruited from the UK between 2006 and 2010.
Participants' dietary assessments over 24 hours were analyzed using the USDA database to calculate flavonoid intake. Ten foods rich in flavonoids were selected based on average daily intake (daily intake). The total intake of the 10 selected foods was summed to calculate the Flavodiet Score (FDS).
Appropriate statistical analyses taking into account potential confounding factors were performed to determine the association between dietary exposure and incident type 2 diabetes.
During the average 12-year study follow-up period, 2,628 new cases of type 2 diabetes were identified.
Intake of flavonoid-rich foods was higher in female participants, older participants, physically active participants, or participants with higher education.
The average total flavonoid intake was 805.7 mg per day. Among the various subclasses, polymers such as proanthocyanidins and flavan-3-ols accounted for 67% and 22% of the total flavonoid intake, respectively. Tea intake was the main source of these two subclasses.
The subclass with the lowest contribution to total flavonoids was flavones, mainly derived from bell pepper.
Analyses adjusted for participants' demographic and lifestyle characteristics revealed that high FDS (six servings of flavonoid-rich foods per day) was associated with a 28% lower risk of developing type 2 diabetes compared with low FDS (one serving of flavonoid-rich foods per day).
Dose-response analysis revealed that one additional serving of flavonoid-rich foods per day was associated with a 6% lower risk of developing diabetes.
When it comes to foods rich in specific flavonoids, studies have found that high intakes of black and green tea, berries, and apples are associated with a 21%, 15%, and 12% lower risk of developing type 2 diabetes, respectively.
With regard to specific flavonoid subclasses, higher intakes of anthocyanins, flavan-3-ols, flavonols, flavones, polymers, and proanthocyanidins were found to be associated with a 19%, 26%, 28%, 19%, 26%, and 27% lower risk of developing diabetes, respectively.
In this study, we analyzed several potential biomarkers related to type 2 diabetes and identified the biological mechanisms responsible for the observed associations.
Mediation analysis identified body mass index (BMI), insulin-like growth factor 1 (IGF-1), C-reactive protein, cystatin C, uric acid, gamma glutamyltransferase (GGT), and alanine aminotransferase (ALT) as potential mediators.
Specifically, the findings suggest that the beneficial effects of a flavonoid-rich diet on weight control, glucose metabolism, basal inflammation, and kidney and liver function may partially contribute to the reduced risk of type 2 diabetes observed in the study.
The study found that foods rich in flavonoids could significantly reduce the risk of type 2 diabetes by regulating obesity, glucose metabolism, inflammation, kidney function, and liver function.
Existing literature suggests that flavonoids, especially anthocyanins, flavan-3-ols, and flavonols, may exert antidiabetic effects by improving insulin secretion and signaling, and promoting glucose transport and metabolism.
As the scientists noted, the study included middle-aged British adults, limiting the generalizability of the results to other non-European populations.
Overall, this study supports current recommendations to increase fruit intake, especially berries and apples, to reduce the risk of type 2 diabetes.