To examine whether positive associations between alcohol and liver enzymes were modified by coffee consumption, smoking, or weight status in a female population.
Regular consumption of beer, wine, and spirits was assessed in a representative cohort of 1462 Swedish women aged 38-60 in 1968, and re-assessed in 1974. In 1980, gamma-glutamyltransferase (GGT) and aspartase transaminase (AST) were measured in 1130 women. Exposures were averaged over values obtained in 1968 and 1974. Multivariable linear regression linked total ethanol intake to log-transformed enzyme values, including interactions by coffee, smoking, and overweight in mutually adjusted models.
Coffee consumption significantly modified the association between ethanol intake and liver enzymes. One g/day higher ethanol intake was associated with 5.5 (3.5, 7.5)% higher values of GGT, and 1.2 (0.4, 2.1)% higher values of AST in women consuming 0-1 cups of coffee per day, while smaller or no effects were observed in women consuming ≥2 cups/day. Synergistic interactions were observed for ethanol and smoking, and for ethanol and overweight. Average alcohol-related effects on GGT in smokers and non-smokers were given by 3.8 (2.7, 4.9)% and 2.1 (0.9, 3.2)% per g ethanol/day, and by 0.9 (0.4, 1.4)% and 0.2 (-0.3, 0.7)% for AST. Similarly, in overweight women, 1 g/day higher ethanol intake was associated with 4.3 (3.0, 5.6)% higher GGT compared to 1.6 (0.7, 2.5)% in non-overweight women.
The results suggest that coffee consumption reduces the enzyme-raising effect of ethanol in the presence of synergistic interactions with smoking and overweight, specifically in women.