Planetary health diet, other plant-based diets and risk of type 2 diabetes: a prospective study from the UK Biobank.

Background: Type 2 diabetes remains a major global health concern, and plant-based diets (PBD) offer substantial preventive value. The Planetary Health Diet Index (PHDI) captures adherence to an environmentally sustainable PBD with potential metabolic benefits. However, evidence on its association with type 2 diabetes risk remains limited, notably in comparison with other preexisting PBD. The objective of this study was to evaluate the association between adherence to the PHDI and type 2 diabetes risk in a large British adult cohort and compare it to other well-known PBDs.

Methods: This analysis included 112,032 participants aged 40-69 years from the UK Biobank who were free of type 2 diabetes and cardiovascular disease at baseline (2009-2012) and were followed until 2021. Dietary intake was assessed using at least two 24-h dietary recalls, and PHDI scores (range: 0-130) were computed based on adherence to 14 food groups recommendations. The other PBDs (alternate Mediterranean Diet score (aMED), healthful plant-based index (hPBD), Dietary Approach to Stop Hypertension (DASH), and Alternate Healthy Eating Index (AHEI-2010)), were estimated using established methodologies. Incident type 2 diabetes was ascertained through clinical records, hospital admissions, and self-reporting. Cox proportional-hazards regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CIs), adjusting for key confounders.

Results: During a median 9.4-year follow-up, 2666 cases of type 2 diabetes were identified. When comparing participants in the highest versus the lowest quartile of PHDI adherence, the multivariable-adjusted HR (95% CI) for type 2 diabetes was 0.57 (0.50, 0.64), which was more pronounced than that observed for the aMED: 0.70 (0.62, 0.78) and hPDI: 0.64 (0.57, 0.72) and similar to DASH: 0.58 (0.51, 0.65); AHEI-2010: 0.59 (0.53, 0.67). Further adjustment for BMI led to a 13-19% attenuation of the association. High consumption of vegetables and fish, and limited intake of red/processed meats and added sugars were associated with reduced type 2 diabetes risk.

Conclusions: In this large cohort of British adults, higher adherence to the PHDI was associated with a substantially lower risk of type 2 diabetes, with effect sizes comparable to or greater than those observed for other well-known PBDs. These findings support the promotion of the PHDI and PBDs as an environmentally sustainable choice with potential to reduce type 2 diabetes risk.