The Portfolio Diet and Incident Type 2 Diabetes: Findings from the Women’s Health Initiative Prospective Cohort Study

Objective: A plant-based dietary pattern, the portfolio diet, has been shown to lower low-density lipoprotein cholesterol and other cardiovascular disease risk factors. However, no study has evaluated the association of this diet with incident type 2 diabetes mellitus. 

Research Design and Methods: This analysis included 145,299 postmenopausal women free of diabetes at baseline in the Women’s Health Initiative (WHI) Clinical Trials and Observational Study from 1993 through to 2021. Adherence to the diet was assessed using a score based on six components (high in plant protein [soy & pulses], nuts, viscous fiber, plant sterols and monounsaturated fat, and low in saturated fat and cholesterol) determined from a validated food frequency questionnaire. We used Cox proportional-hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CI) of the association of the portfolio diet, alongside the Dietary Approaches to Stop Hypertension (DASH) and Mediterranean diets, with incident type 2 diabetes, adjusting for potential confounders. 

Results: Over a mean follow-up of 16.0 years, 13,943 cases of incident type 2 diabetes were identified. Comparing the highest with the lowest quintiles of adherence, the HRs for risk of incident type 2 diabetes were 0.77 (95% CI, 0.72, 0.82) for the portfolio diet, 0.69 (0.64, 0.73) for the DASH diet, and 0.78 (0.74, 0.83) for the Mediterranean diet. These findings were attenuated by 10% after additional adjustment for BMI. 

Conclusions: Higher adherence to the plant predominant portfolio, DASH and Mediterranean diets were prospectively associated with a lower risk of type 2 diabetes in postmenopausal women.