The Association between Dietary Nitrate Intake and Alanine Transaminase in Adolescent Girls

Introduction: The effects of dietary nitrate on health are controversial. The current study aims to investigate the relationship between dietary intake of nitrate and liver enzymes among Iranian adolescent girls. Materials and Methods: This cross sectional study was conducted on 733 adolescent girls. They were recruited from several schools in different areas in the cities of Mashhad and Sabzevar, northeast region of Iran, by random cluster sampling method. The dietary intake of nitrate was assessed using a validated food-frequency questionnaire (FFQ). Levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) were measured by auto-analyzer. Linear regression was applied to investigate the correlation between nitrate intake and liver enzymes in crude and adjusted models. Results: There was a direct association between dietary intake of nitrate and serum levels of ALT in crude [β = 0.117; 95% CI (0.003-0.016); P 0.01] and adjusted models for energy intake, age, BMI percentile, physical activity, menstruation, father s education, and mother s education [β = 0.128; 95% CI (0.003-0.016); P 0.01]. No significant associations were found between dietary intake of nitrate and levels of ALP, AST, and GGT in crude or adjusted models. Conclusion: There was a direct relationship between dietary intake of nitrate and serum concentration of ALT. Longitudinal studies are required to examine the association between dietary nitrate intake and liver functional tests.