Association Between Dietary Acid Load and Incident Diabetes Risk Among Japanese Adults: Findings From The Japan Collaborative Cohort Study

Dietary acid load (DAL), which reflects diet's overall acid-base balance, has been proposed to influence glucose metabolism; however, epidemiological findings on its relationship with diabetes risk remain inconsistent. While Western studies suggest that higher DAL is associated with higher diabetes risk, particularly among women, findings from East Asian populations have been inconsistent, particularly regarding sex-specific associations. The present prospective study examined the association between DAL and 5-year diabetes incidence among Japanese adults, focusing on sex-specific differences. Data were obtained from 19,040 participants (7,037 men and 12,003 women) in the Japan Collaborative Cohort Study. DAL was estimated based on the potential renal acid load (PRAL) and net endogenous acid production (NEAP) derived from a validated food-frequency questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) for incident diabetes were estimated separately for men and women across PRAL and NEAP quartiles using multivariable logistic regression with multiple imputations for missing covariates. During follow-up, 490 new diabetes cases were identified (245 in each sex). Among women, higher DAL was significantly associated with a higher risk of diabetes; ORs (95% CIs) from multivariable-adjusted model, including sociodemographic, lifestyle, health status, and macronutrient covariates, comparing the highest with the lowest quartiles were 1.61 (1.09-2.37) for PRAL and 1.72 (1.18-2.52) for NEAP. No clear associations were observed among men. The findings provide a foundation for further studies in East Asian populations using more precise dietary assessment methods to clarify the association between DAL and incident diabetes and to inform dietary guidelines and preventive strategies.