Association Between the Planetary Health Diet Index and Serum Uric Acid Levels and Incident Hyperuricemia: Findings From an Iranian Prospective Cohort Study.

The EAT-Lancet planetary health diet aims to jointly promote human health and environmental sustainability, yet its relationship with uric acid metabolism remains largely unexplored. We prospectively examined the association between adherence to this dietary pattern and both incident hyperuricemia and serum uric acid levels, and tested whether insulin resistance mediated any observed link. Among 5773 Iranian adults free of hyperuricemia at baseline and followed for approximately five years, dietary intake was assessed using a validated food frequency questionnaire. Adherence to the EAT-Lancet diet was quantified with the Planetary Health Diet Index (PHDI; range 0-150). Hyperuricemia was defined as serum uric acid exceeding 7.0 mg/dL in men and 6.0 mg/dL in women. Multivariable logistic and linear regression models estimated associations, and bootstrapped causal mediation analysis quantified the indirect effect through HOMA-IR. Incident hyperuricemia occurred in 1113 participants (cumulative incidence 19.3%). In the fully adjusted model, the highest versus lowest PHDI quartile was associated with 25% lower odds of hyperuricemia (OR 0.75; 95% CI 0.62-0.91; p-trend < 0.001). Each SD increment in PHDI corresponded to a 0.053 mg/dL lower follow-up serum uric acid after adjustment for baseline levels (p < 0.001). Mediation analysis suggested that HOMA-IR accounted for a large proportion of the association (point estimate 91.0%; 95% CI 48.2%-232.5%), although the wide confidence interval calls for cautious interpretation; the direct effect was non-significant. Findings were robust across sensitivity analyses, alternative EAT-Lancet scoring systems, and further adjustment for established dietary indices including the Mediterranean diet score, Healthy Eating Index 2015, Diet Quality Index Revised, and Dietary Approaches to Stop Hypertension score. Greater adherence to the planetary health diet was prospectively associated with lower serum uric acid and reduced hyperuricemia odds, a benefit that appeared to be mediated largely through insulin sensitivity.