Foods and drinks rich in flavonoids reduce the risk of type 2 diabetes by up to 28%

New research published in Nutrition & Diabetes, examined the association between a flavonoid-rich diet and the development of type 2 diabetes in a large UK population.

It is already known that a diet rich in plant foods reduces the risk of type 2 diabetes. However, plants are rich in a variety of polyphenolic compounds that vary in their bioavailability and bioactivity.

Flavonoids, a category of polyphenolic compounds, are divided into six main subclasses: flavanones, flavones, flavan-3-ols, flavonols, anthocyanins, and isoflavones.

There is some evidence that indicates that increased intake of flavonoids may lead to increased insulin sensitivity and improved blood lipid profile.

Study of flavonoid intake and risk of type 2 diabetes

The new study included 113,097 participants from the UK Biobank, a large population-based cohort study that recruited more than 500,000 adults in the UK from 2006 to 2010.

Participants' flavonoid intake was assessed through two or more 24-hour dietary surveys, which were analyzed using US Department of Agriculture databases.

Ten flavonoid-rich foods were selected based on average daily intake. The Flavodietary Index (FDS) was calculated by summing the servings of these ten foods.

Statistical analyzes controlling for potential confounders were performed to evaluate the association between flavonoid intake and the development of type 2 diabetes.

The study found that higher intake of flavonoid-rich foods was more common among women, older adults, those with an active lifestyle, and people with a high level of education.

The average daily intake of flavonoids was 805.7 milligrams. Among the flavonoid subclasses, polymers—including proanthocyanidins—and flavan-3-ols were the main contributors, accounting for 67% and 22% of total intake, respectively.

Tea was the main source for these subclasses. Flavones, mainly derived from peppers, contributed the least to total flavonoid intake.

The study took into account the demographics and lifestyle of participants when analyzing the association between flavonoid intake and the risk of developing type 2 diabetes.

A higher Flavodietary Index (FDS)—equivalent to consuming six servings of flavonoid-rich foods per day—was found to be associated with a 28% lower risk of developing type 2 diabetes compared with a lower FDS equal to one serving per day.

The study found that each additional daily serving of flavonoid-rich foods reduced the risk of diabetes by 6%, 4 servings of black or green tea per day was associated with a 21% lower risk, 1 serving of berries per day was associated with a 15% lower risk. Risk of diabetes, and 1 serving of apples per day is associated with a 12% lower risk.

Flavonoids reduce inflammation and help control blood sugar

Analysis identified body mass index (BMI), insulin-like growth factor 1 (IGF-1), C-reactive protein, cystatin C, urate, gamma-glutamyltransferase (GGT), and alanine aminotransferase (ALT) as potential mediators.

The results suggest that a diet rich in flavonoids has positive effects on weight management, glucose metabolism, inflammation, and kidney and liver function, which may help reduce the risk of type 2 diabetes.

Flavonoids, especially anthocyanins, flavan-3-ols and flavonols, enhance insulin secretion and signaling, and improve glucose transport and metabolism.

However, the study results may not be applicable to non-European populations as the study included middle-aged British adults.