Prospective Study of Plant-Based Dietary Patterns and Diabetes in Puerto Rican Adults

Background: Vegetarian-type dietary patterns have been associated with reducing the risk of developing diabetes and may function as an effective strategy for diabetes management. Objectives: We aimed to examine the associations between adherence to plant-based diet indices and the risk of developing diabetes in the Boston Puerto Rican Health Study. Methods: Puerto Rican adults (n = 646), aged 45-75 y and free of diabetes at baseline, were included. Dietary intake was assessed via a validated FFQ. Three plant-based dietary indices were calculated: an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). Incident diabetes was defined as fasting plasma glucose ≥ 126 mg/dL (7.0 mmol/L), glycated hemoglobin ≥ 6.5% (48 mmol/mol), or use of hypoglycemic agents during follow-up. Cox proportional hazards were used to evaluate associations between the dietary patterns and incidence of diabetes, adjusting for potential confounders, such as age, sex, socioeconomic status, lifestyle factors, obesity, total energy intake, depressive symptomatology, and plasma concentrations of lipids. Results: During a mean of 4.2 y of follow-up, we identified 134 diabetes cases. After adjustment for covariates, higher hPDI was associated with lower risk of developing diabetes (adjusted HR for the highest compared with the lowest tertile: 0.54; 95% CI: 0.31, 0.94; P-trend = 0.03). In contrast, the PDI and uPDI were not significantly associated with the risk of diabetes (P-trend > 0.3 for both). Conclusions: The healthful plant-based dietary index, but not the total plant-based dietary index, was inversely associated with diabetes risk. These findings suggest that the quality of plant-based diets must be considered when recommending plant-based diets for the prevention of diabetes. This trial was registered at clinicaltrials.gov as NCT01231958.