A Healthful Plant-Based Eating Pattern Is Longitudinally Associated with Higher Insulin Sensitivity in Australian Adults

Abstract

Background: A healthful plant-based eating pattern is associated with lower type 2 diabetes risk; however, the association with its preceding state, impaired insulin sensitivity, is less well established, particularly in younger populations with repeated measures of diet over time.

Objective: We aimed to examine the longitudinal relationship between a healthful plant-based eating pattern and insulin sensitivity in young to middle-aged adults.

Methods: We included 667 participants from the Childhood Determinants of Adult Health (CDAH) study, a population-based cohort in Australia. Healthful plant-based diet index (hPDI) scores were derived from food frequency questionnaire data. Plant foods considered "healthful" were scored positively (e.g., whole grains, fruit, vegetables), with all remaining foods scored reversely (e.g., refined grains, soft drinks, meat). Updated homeostatic model assessment (HOMA2) estimated insulin sensitivity from fasting insulin and glucose concentrations. We used linear mixed-effects regression to analyze data from 2 time points: CDAH-1 (2004-2006, 26-36 y of age) and CDAH-3 (2017-2019, 36-49 y of age). hPDI scores were modeled as between- and within-person effects (i.e., a participant's overall mean and their deviation from said mean at each time point, respectively).

Results: The median follow-up duration was 13 y. In our primary analysis, each 10-unit difference in hPDI score was associated with higher log-HOMA2 insulin sensitivity [95% confidence interval], with between-person (β = 0.11 [0.05, 0.17], P < 0.001) and within-person effects (β = 0.10 [0.04, 0.16], P = 0.001). The within-person effect persisted despite accounting for compliance with dietary guidelines. Adjustment for waist circumference attenuated the between-person effect by 70% (P = 0.26) and the within-person effect by 40% (P = 0.04).

Conclusions: In young to middle-aged Australian adults, a healthful plant-based eating pattern (determined using hPDI scores) was longitudinally associated with higher insulin sensitivity, and therefore, potentially lower type 2 diabetes risk later in life.

Keywords: adult; dietary guidelines; insulin sensitivity; longitudinal studies; plant-based diet; type 2 diabetes mellitus.