Coffee drinking and serum gamma-glutamyltransferase: An extended study of self defense officials of Japan

PURPOSE: To examine the effect of coffee drinking on serum,gamma-,glutamyltransferase (GGT) level in relation to alcohol drinking, smoking, and degree of obesity in middle-aged Japanese men. METHODS: From 1986 to 1994, a total of 7637 male officials of the Self-Defense Forces of Japan aged 48-59 years received a preretirement health examination. Coffee drinking was ascertained by a self-administered questionnaire, and serum GGT level was measured. After excluding 1360 men with a possible pathologic condition influencing liver enzyme levels and 182 former alcohol drinkers, effect of coffee drinking on serum GGT was examined by a multiple linear regression model and analysis of variance adjusting for alcohol drinking, smoking, and body mass index (BMI). RESULTS: The adjusted percentage of difference in serum GGT was -4.3 (95% CI = -5.0; -3.5) per cup of coffee. The inverse coffee-GOT relation was most prominent among men drinking greater than or equal to 30 mi of ethanol and smoking greater than or equal to 15 cigarettes daily; and positive associations of alcohol and smoking with GGT were attenuated by coffee drinking, more clearly among men with BMI greater than or equal to 25.00 kg/m(2),. Adjusted percentages of difference in serum GGT were - 2.6% (P = 0.0003) per cup of brewed coffee, and - 5.1% (p = 0.0001) per cup of instant coffee, independently of each other. CONCLUSIONS: The present study suggests that coffee consumption may weaken GGT-induction by alcohol, and possibly by smoking. These effect modifications by coffee may differ according to the degree of obesity. (C) 1999 Elsevier Science Inc. All rights reserved.