Alcohol, Liver Enzymes, and Risk for Type 2 Diabetes
Moderate alcohol consumption decreases the risk of type 2 diabetes (DM), but elevated liver enzymes increase the risk. This study examined the association between DM; alcohol consumption; and two liver enzymes, γ-glutamyltransferase (GGT) and alanine aminotransferase (ALT). Researchers followed a cohort of 8576 Japanese men aged 40–55 years enrolled in the Kansai Healthcare Study, an ongoing investigation of risk factors for cardiometabolic disease. Four years following baseline examination, DM was diagnosed in 878 subjects. Results in multivariable models were as follows:
Alcohol intake of 16–43 g per day (1½–3½ drinks) decreased the risk of DM, while higher levels of GGT and ALT increased the risk.
In joint analyses of alcohol and enzymes, moderate drinkers with the lowest tertile of GGT had the lowest risk of DM, while nondrinkers with the highest tertile of GGT or ALT had the highest risk (odds ratio, 3.18 and 2.37, respectively).
At every level of GGT, moderate or heavy alcohol drinkers had a lower risk of DM than nondrinkers.
Although these findings indicate that GGT, ALT, and alcohol consumption are independently associated with DM risk and point to an inverse association between alcohol and DM (30–35% lower risk for moderate drinkers), interpreting the results is problematic in that multivariable analyses were not adjusted for liver enzymes. The raw data suggest a higher risk of DM not only among nondrinkers but also among heavier drinkers. Once liver enzyme data are entered into the analysis, however, even heavier drinkers show a marked decrease in risk. In addition, the highest risk of DM was almost always in nondrinkers with abnormal liver tests, raising the question of whether some subjects who were nondrinkers at baseline were former heavy drinkers. Although prospective epidemiologic studies consistently show a much lower risk of developing DM among moderate drinkers, analytic problems in the present paper make it difficult to conclude that the effect of alcohol on risk of DM is independent of liver function.
Sato KK, Hayashi T, Nakamura Y, et al. Liver enzymes compared with alcohol consumption in predicting the risk of type 2 diabetes: the Kansai Healthcare Study. Diabetes Care. 2008;31(6):1230–1236.