Type 2 diabetes: Flavonoid-rich diets may help lower risk

The new study involved 113,097 participants from the UK Biobank, a large-scale, population-based cohort study that recruited over 500,000 adults in the UK between 2006 and 2010.

The participants’ flavonoid intake was assessed through two or more 24-hour dietary surveys, which were analysed using the United States Department of Agriculture databases.

Ten flavonoid-rich foods were chosen based on average daily consumption. A Flavodiet Score (FDS) was calculated by summing the servings of these ten foods.

Statistical analyses, accounting for potential confounders, were performed to assess the relationship between dietary flavonoid intake and the development of type 2 diabetes.

The study found that higher consumption of flavonoid-rich foods was more common among female participants, older individuals, those who were physically active and those with higher educational levels.

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

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

When analyzing the association between flavonoid intake and the risk of developing type 2 diabetes, the study adjusted for participants’ demographic and lifestyle characteristics.

It found that a higher Flavodiet Score (FDS) — equivalent to consuming six servings of flavonoid-rich foods per day — was linked to a 28% lower risk of developing type 2 diabetes compared to a lower FDS of one serving per day.

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

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

The findings suggest that a flavonoid-rich diet positively impacts weight management, glucose metabolism, inflammation and kidney and liver functions, contributing to the reduced risk of type 2 diabetes.

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

However, the study’s findings may not be generalisable to non-European populations as the study population consisted of middle-aged British adults.

Two experts, not involved in this research, spoke to Medical News Today about its findings.

Megan Hilbert, RDN, a registered dietitian specialising in gut health nutrition and the gut-brain axis, told MNT that “these findings help to confirm a lot of what we understand about the pathophysiology of type 2 diabetes.”

“This study confirms flavonoids impact on this, due to flavonoids’ ability to help reduce inflammation and even help those with high intakes maintain a healthy weight,” she explained.

“These findings show that flavonoid intake can help lower excess adipose tissue which can be pro-inflammatory, as well as reduce adipose tissue that surrounds smooth muscle tissue, allowing for more blood glucose to be absorbed by said muslce cells,” Hilbert added.

“These changes help allow the body to process blood sugars more effectively, leading to a reduced risk in developing type 2 diabetes,” she said.

“What I really enjoyed about this study is that different flavonoids were compared and the data showed certain flavonoids to have a larger impact on reductions in diabetes, and certain foods in particular seemed to have a more protective effect than others. These specific findings can play a huge role in educating patients on dietary recommendations.”

– Megan Hilbert, RDN

Kelsey Costa, MS, RDN, a registered dietitian nutritionist and founder of Dietitian Insights, agreed, noting that “given flavonoids’ well-documented anti-diabetic effects, the results of the present study are not surprising.

According to Costa, flavonoids’ role in blood sugar control may also explain their link to lower diabetes risk:

“Flavonoids may help prevent and manage diabetes and its complications by regulating glucose metabolism, enhancing insulin signaling and secretion and liver enzyme activity, reducing oxidative stress, and optimizing lipid profiles, which together improve obesity, blood sugar levels, chronic inflammation, and kidney and liver function.”

“However, the large UK Biobank cohort and substantial follow-up add further evidence to support flavonoids’ protective role in preventing type 2 diabetes,” she cautioned.

In addition, she highlighted that the “scientific community continues to uncover the harmful effects of alcohol consumption, including its association with systemic inflammation, weight gain, and disturbances in fat metabolism, which can ultimately contribute to the development of type 2 diabetes.”

“Therefore, I am pleased that this study accounted for the total alcohol intake of participants when examining the relationship between flavonoid consumption and type 2 diabetes risk in their initial assessment and then reassessed the data by excluding red wine from the flavonoid diet score to determine if the results would differ,” Costa told us.

She further noted that “[t]his approach allowed them to isolate the effects of flavonoids without the influence of alcohol and show that the protective association between flavonoid intake and type 2 diabetes risk remained significant without any red wine consumption.”

“We’re finding out that consuming no alcohol is better for your health across the board, with several studies highlighting that even moderate alcohol consumption can lead to detrimental health effects, so it’s essential to account for alcohol intake when assessing the impact of other dietary factors.”

– Kelsey Costa, RDN

“By prioritizing a diet rich in naturally occurring flavonoids from sources such as fruits, vegetables, and teas, individuals can enhance their overall health and lower their risk of chronic conditions without the negative impacts associated with alcohol consumption,” Costa explained.

Patients are advised to increase their intake of flavonoid-rich foods as it has the potential to significantly reduce the risk of type 2 diabetes.

“The study identifies achievable goals, such as consuming six daily servings of a variety of flavonoid-rich foods, including grapes, oranges, grapefruit, sweet peppers, onions, at least 70% dark chocolate, and especially black and green tea, apples, and berries,” said Costa.

“Despite the need for further research, these recommendations offer practical steps for improving health by emphasizing the importance of including flavonoid-rich foods as part of a balanced, health-promoting lifestyle,” she added. “While more targeted studies are needed to pinpoint the most anti-diabetic foods or the specific amounts to consume, incorporating flavonoid-rich foods daily can undoubtedly offer substantial health benefits.”

Costa concluded that “this approach allows individuals to take proactive steps to enhance their well-being even as the science continues to evolve.”