Flavonoid-rich diet may reduce risk for type 2 diabetes
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Key takeaways:
- Eating six servings of flavonoid-rich foods a day was linked to a 26% lower risk for type 2 diabetes.
- Individual flavonoid subclasses were tied to risk reductions ranging from 19% to 28%.
Consuming more flavonoids and flavonoid-rich foods such as tea, berries and apples was associated with a lower risk for type 2 diabetes, researchers found.
According to Alysha S. Thompson, a PhD student at Queen’s University Belfast in Ireland, and colleagues, flavonoids are a class of polyphenolic compounds “that are commonly found in fruits, vegetables, dark chocolate, tea and red wine.”
Emerging evidence suggests that higher intakes of flavonoid subclasses — including flavanones, flavones, flavan-3-ols, proanthocyanidins, flavonols, anthocyanins and isoflavones — through flavonoid-rich food “improves insulin sensitivity, insulin resistance and lipid profiles,” they wrote.
In the study, published in Nutrition and Diabetes, Thompson and colleagues evaluated the effects of a diet high in flavonoid foods on the risk for type 2 diabetes among 113,097 participants (mean age at enrollment, 56 years; 57% women) from the U.K. Biobank cohort.
The researchers identified 2,628 incident cases of type 2 diabetes over a median follow-up period of 12 years.
A higher Flavodiet Score — regarded as six servings of flavonoid-rich foods per day — was associated with a 28% lower risk for type 2 diabetes (HR = 0.72; 95% CI, 0.64-0.81) vs. a lower Flavodiet Score, characterized as one serving of flavonoid-rich foods a day, according to Thompson and colleagues. However, the risk reduction fell to 26% (HR = 0.74; 95% CI, 0.66-0.84) when red wine was removed from the Flavodiet Score.
The researchers identified individual foods and beverages that lowered the risk for type 2 diabetes. For example, four servings of black or green tea a day was associated with a 21% lower risk (HR = 0.79; 95% CI, 0.7-0.9), one serving of berries a day was associated with a 15% lower risk (HR = 0.85; 95% CI, 0.74-0.98) and one serving of apples a day was associated with a 12% lower risk (HR = 0.88; 95% CI, 0.79-0.98). The findings persisted even after the researchers adjusted the analyses for demographic and lifestyle characteristics.
“This indicates that the observed beneficial effects on health may not be solely explained through overall improved diet quality, but rather something specifically present in flavonoid-rich plant foods,” they wrote.
When looking at subclasses, Thompson and colleagues found that higher intakes of flavones, proanthocyanidins, polymers, flavonols, flavan-3-ols and anthocyanins were associated with a 19%, 27%, 26%, 28%, 26% and 19% reduced risk for type 2 diabetes, respectively.
The results could be attributed to the benefits of a flavonoid-rich diet on sugar metabolism, obesity, liver status, kidney function and basal inflammation, according to the researchers.
“Our finding underlines that flavonoid intake may reduce weight gain through numerous mechanisms, including increased satiety and energy metabolism,” they wrote. “Similarly, it has been proposed that flavonoids may enhance kidney function, and our findings suggest that habitual flavonoid intake may indeed protect against early kidney dysfunction before diabetes is diagnosed.”
There were a couple study limitations. For example, Thomson and colleagues said they could not rule out underreporting or recall bias, and residual confounders may have impacted the associations.
They concluded that the study supports current recommendations to increase fruit consumption to help prevent type 2 diabetes “but points to a specific role for berries and apples.”