Influence of coffee intake on urinary hippuric acid concentration

Intake of foods and drinks containing benzoic acid influences the urinary hippuric acid (HA) concentration, which is used to monitor toluene exposure in Japan. Therefore, it is necessary to control the intake of benzoic acid before urine collection. Recently, some reports have suggested that components of coffee, such as chlorogenic, caffeic, and quinic acids are metabolized to HA. In this study, we evaluated the influence of coffee intake on the urinary HA concentration in toluene-nonexposed workers who had controlled their benzoic acid intake, and investigated which components of coffee influenced the urinary HA concentration. We collected urine from 15 healthy men who did not handle toluene during working hours, after they had consumed coffee, and we measured their urinary HA concentrations; the benzoic acid intake was controlled in these participants during the study period. The levels of chlorogenic, caffeic, and quinic acids in coffee were analyzed by LC-MS/MS. Urinary HA concentration increased significantly with increasing coffee consumption. Spectrophotometric LC-MS/MS analysis of coffee indicated that it contained chlorogenic and quinic acids at relatively high concentrations but did not contain benzoic acid. Our findings suggest that toluene exposure in coffee-consuming workers may be overestimated.