The objective is to evaluate the efficacy of anthocyanin-rich purple-fleshed sweet potato (PSP) beverage on the serum levels of gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in healthy Caucasians with borderline hepatitis. Forty healthy Caucasians (41-69 years) consumed three bottles of the PSP beverage (177 mg anthocyanins per 125-ml bottle) or placebo (1.3 mg) per day for 8 weeks. Thirty-nine subjects completed the study and two subjects were excluded from statistical analysis. GGT levels in the PSP group on days 15 and 43 were lower (P = 0.077 and 0.038, respectively), AST levels in the PSP group on days 29 and 43 were lower (P = 0.010 and 0.045, respectively) and ALT level in the PSP group on day 43 was lower (P = 0.037) than in the placebo group. The PSP beverage did not induce clinically relevant changes in other blood and clinical chemistry parameters.