Longitudinal Associations of Total and Class-Specific Polyphenol Intake with Incident Type 2 Diabetes and Changes in Glycemic Markers: Findings from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) Cohort

BACKGROUND: The prevalence of type 2 diabetes (T2D) is rapidly increasing worldwide, particularly in low- and middle-income countries, and can lead to severe health complications. Dietary polyphenols may help prevent T2D and support metabolic health.

OBJECTIVES: This study aimed to investigate the longitudinal associations between dietary polyphenol intake and risk of incident T2D and changes in glycemic markers [fasting glucose, glycated hemoglobin (HbA1c), and homeostasis model assessment of insulin resistance (HOMA-IR)] in participants of the Brazilian Longitudinal StudyIn a longitudinal study, researchers conduct several observations of the same participants over a pe... of Adult Health.

METHODS: A total of 8781 participants (mean age 58.8 y, 61.3% female) free of diabetes at baseline were followed for a median of 7.6 y. Dietary polyphenol intake was assessed via a semiquantitative food frequency questionnaire at 2 time points, with polyphenol content estimated from the Phenol-Explorer database. Cox proportional hazards regression with time-varying exposure was used to assess associations between polyphenol intake tertiles and incident T2D. Linear regression models were used to examine associations with changes in glycemic markers between waves.

RESULTS: During follow-up, 1453 incident T2D cases were identified. In the fully adjusted model, participants in the highest tertile of total polyphenol intake had a 19% lower risk of incident T2D than those in the lowest tertile (hazard ratio: 0.81; 95% confidence interval: 0.70, 0.93). Significant inverse associations were also observed for phenolic acids, hydroxycinnamic acids, total flavonoids, flavan-3-ol monomers, flavan-3-ol dimers to polymers, flavones, anthocyanins, and stilbenes, with risk reductions ranging from 13% to 27%. Participants in the highest tertile of total polyphenols, phenolic acids, and stilbenes showed significantly smaller increases in HOMA-IR over follow-up. No significant associations were observed for fasting glucose or HbA1c.

CONCLUSIONS: Higher dietary polyphenol intake is inversely associated with incident T2D and attenuates insulin resistance progression over time. These findings support polyphenol-rich dietary patterns as a strategy for T2D risk reduction.