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-,glutamylt ransferase (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-Defe nse Forces of Japan aged 48-59 years received a preretirement health examin ation. Coffee drinking was ascertained by a self-administered questionnaire , and serum GGT level was measured. After excluding 1360 men with a possibl e pathologic condition influencing liver enzyme levels and 182 former alcoh ol drinkers, effect of coffee drinking on serum GGT was examined by a multi ple 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% C I = -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 associa tions of alcohol and smoking with GGT were attenuated by coffee drinking, m ore clearly among men with BMI greater than or equal to 25.00 kg/m(2),. Adj usted percentages of difference in serum GGT were - 2.6% (P = 0.0003) per c up of brewed coffee, and - 5.1% (p = 0.0001) per cup of instant coffee, ind ependently of each other. CONCLUSIONS: The present study suggests that coffee consumption may weaken GGT-induction by alcohol, and possibly by smoking. These effect modificatio ns by coffee may differ according to the degree of obesity. (C) 1999 Elsevi er Science Inc. All rights reserved.