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We investigated the relation between coffee drinking and serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations among 7313 Japanese men receiving a health examination, excluding former alcohol drinkers and men with a history of chronic liver disease. Serum AST > 40 and/or ALT > 40 U/L was defined as liver inflammation. Adjustment was made for alcohol use, smoking, body mass index, serum marker for hepatitis virus infection, and other possible confounders. Adjusted odds ratios of liver inflammation were 1.00 (reference), 0.80, 0.69, and 0.61 for men drinking < 1, 1-2, 3-4, and > or = 5 cups of coffee daily, respectively. Among 6898 men without liver inflammation, serum AST and ALT were inversely associated with coffee consumption, and alcohol-related rise in AST was attenuated with coffee drinking. These findings suggest coffee may have an effect of suppressing the rise of serum aminotransferase, partly by inhibiting the alcohol-related elevation. Studies regarding biological mechanism are warranted.

Consumption of caffeine-rich beverages, which have diuretic properties, may decrease serum uric acid concentrations. We examined cross-sectionally the relationship of coffee and green tea consumption to serum uric acid concentrations in 2240 male self-defence officials who received a pre-retirement health examination at four hospitals of the Self-Defence Forces between 1993 and 1994. The mean levels of coffee and green tea consumption were 2.3 and 3.1 cups/d respectively. There was a clear inverse relationship between coffee consumption and serum uric acid concentration. When adjusted for hospital only, those consuming less than one cup of coffee daily had a mean serum uric acid concentration of 60 mg/l, while that of those drinking five or more cups of coffee daily was 56 mg/l (P < 0.0001). No such relationship was observed for green tea, another major dietary source of caffeine in Japan. The relationship between coffee consumption and serum uric acid concentration was independent of age, rank in the Self-Defence Forces, BMI, systolic blood pressure, serum creatinine, serum total cholesterol and serum HDL-cholesterol concentrations, smoking status, alcohol use, beer consumption and intake of dairy products. These findings suggest that coffee drinking may be associated with lower concentrations of serum uric acid, and further studies are needed to confirm the association.

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 7,637 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 1,360 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-GGT relation was most prominent among men drinking > or = 30 ml of ethanol and smoking > or = 15 cigarettes daily; and positive associations of alcohol and smoking with GGT were attenuated by coffee drinking, more clearly among men with BMI > or = 25.00 kg/m2. 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.

The study aims to examine the relationship between habitual coffee consumption and blood pressure. The subjects were 3336 male self-defense officials aged 48-56 years, who received a preretirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and December 1992. Average coffee intake in the past year was ascertained by a self-administered questionnaire. A significant inverse relation between habitual coffee consumption and blood pressure was found with and without adjustment for alcohol use, cigarette smoking, body mass index, glucose tolerance, and green tea intake. Green tea, another major source of caffeine intake in Japanese, was unrelated to blood pressure. The adjusted mean differences per cup of coffee consumed per day were -0.6 mmHg (95% confident interval [CI]: -0.9 to -0.3, p = 0.0001) in systolic blood pressure and -0.4 mmHg (95% CI: -0.5 to -0.2, p = 0.0002) in diastolic blood pressure. Habitual coffee drinkers had lower blood pressure than non-drinkers at any levels of alcohol use, cigarette smoking, obesity, and glucose intolerance. Our findings consolidate the previous observation that habitual coffee consumption was associated with lower blood pressure.

The relation of coffee drinking and other behavioral factors to serum gamma-glutamyltransferase (GGT) was examined in 2,494 male self-defense officials aged 48-56 years, who received a retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and December 1990. Coffee, but not green tea, consumption was inversely related to serum GGT independently of body mass index, alcohol use, and smoking. All of the latter variables were also independently and positively associated with serum GGT. Lower levels of serum GGT associated with coffee drinking were more evident among heavier alcohol drinkers and also among heavier smokers. The findings suggest that coffee may inhibit the inducing effects of alcohol and possibly of smoking upon GGT in the liver.