High Dietary Sodium Intake Assessed by Estimated 24-h Urinary Sodium Excretion Is Associated with NAFLD and Hepatic Fibrosis

BACKGROUND Although high sodium intake is associated with obesity and hypertension, few studies have investigated the relationship between sodium intake and non-alcoholic fatty liver disease (NAFLD). We evaluated the association between sodium intake assessed by estimated 24-h urinary sodium excretion and NAFLD in healthy Koreans. METHODS We analyzed data from 27,433 participants in the Korea National Health and Nutrition Examination Surveys (2008-2010). The total amount of sodium excretion in 24-h urine was estimated using Tanaka's equations from spot urine specimens. Subjects were defined as having NAFLD when they had high scores in previously validated NAFLD prediction models such as the hepatic steatosis index (HSI) and fatty liver index (FLI). BARD scores and FIB-4 were used to define advanced fibrosis in subjects with NAFLD. RESULTS The participants were classified into three groups according to estimated 24-h urinary excretion tertiles. The prevalence of NAFLD as assessed by both FLI and HSI was significantly higher in the highest estimated 24-h urinary sodium excretion tertile group. Even after adjustment for confounding factors including body fat and hypertension, the association between higher estimated 24-h urinary sodium excretion and NAFLD remained significant (Odds ratios (OR) 1.39, 95% confidence interval (CI) 1.26-1.55, in HSI; OR 1.75, CI 1.39-2.20, in FLI, both P < 0.001). Further, subjects with hepatic fibrosis as assessed by BARD score and FIB-4 in NAFLD patients had higher estimated 24-h urinary sodium values. CONCLUSIONS High sodium intake was independently associated with an increased risk of NAFLD and advanced liver fibrosis.