Evaluation of reference intervals for biomarkers sensitive to alcohol consumption, excess body weight and oxidative stress

Background. Unexplained liver enzyme activities are often found in health screening programs and constitute an increasingly common cause for referral to specialized clinics. Recent studies have indicated that both excess body weight and alcohol consumption may lead to metabolic aberrations which are readily reflected in the activities of liver enzymes in circulation. Materials and methods. We compared various laboratory markers and their upper normal limits in relation to information on alcohol consumption and BMI in a large population of apparently healthy individuals collected from Nordic countries. Results. Based on the data obtained from normal weight abstainers (BMI 19-25 kg/m<SU2</SU) the upper normal limits in men should be 50 U/L for ALT, and 45 U/L (< 40 years) and 70 U/L (>= 40 years) for GGT, while the current recommendations are 70 U/L, 80 U/L, and 115 U/L, respectively. Already in comparisons between normal weight abstainers and corresponding moderate drinkers notable impacts (+14% - +74%) on upper limits for these analytes were seen, which further grew when adiposity occurred together with alcohol drinking (+75% - +186%, BMI >= 27 kg/m<SU2</SU). In addition to liver enzymes, similar changes were also found for uric acid. Conclusions. Alcohol consumption and excess body weight even in apparently healthy individuals have a significant influence on liver enzyme activities, which may be due to a cumulative oxidative stress burden. The metabolic changes induced by adiposity or ethanol intake should be considered in the definition of normal ranges for all laboratory parameters sensitive to oxidative stress.