Dietary acid load and mortality among Japanese men and women: the Japan Public Health Center-based Prospective Study

Background: Diet-induced metabolic acidosis has been linked to cardiometabolic abnormalities including hypertension and type 2 diabetes. However, there are limited data on its association with other chronic diseases and mortality. Objective: The present study aimed to examine the association between dietary acid load and total and cause-specific mortality. Design: This study was a large-scale, population-based, prospective cohort study in Japan involving 42,736 men and 49,742 women, aged 45-75 y, who had no history of cancer, stroke, ischemic heart disease (IHD), or chronic liver disease at baseline. Dietary intake was assessed by using a validated 147-item food-frequency questionnaire. Potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores were derived from nutrient intake. Death and cause of death were identified by using the residential registry and death certificates. Cox proportional hazards regression was used to estimate HRs and 95% CIs for total and cause-specific mortality with adjustment for potential confounding variables. Results: During a median follow-up of 16.9 y, 12,993 total deaths occurred. A higher PRAL score was associated with higher total mortality: the multivariable-adjusted HR for total mortality for the highest compared with the lowest quartiles of PRAL scores was 1.13 (95% CI: 1.07, 1.18; P-trend < 0.001). This score was positively associated with mortality from cardiovascular disease (CVD) and particularly from IHD; the HRs (95% CIs) for the highest compared with the lowest quartile of PRAL score were 1.16 (1.06, 1.28) and 1.16 (1.02, 1.33) for CVD and IHD mortality, respectively. There was no association between PRAL score and cancer mortality. Similar associations were observed between NEAP score and total and cause-specific mortality. Conclusion: A high dietary acid load score was associated with a higher risk of total mortality and mortality from CVD, particularly from IHD, in Japanese adults.