Catechins, compounds derived from green tea, have been shown to reduce plasma cholesterol levels and the rate of cholesterol absorption. We investigated the dose response and the mechanism of action of epigallocatechin gallate (EGCG) on these parameters in rats. Wistar rats were fed a diet high in cholesterol and fat containing either none, 0.25% (0.2 g/day/kg BW), 0.5% (0.4 g/day/kg/BW) or 1.0% (0.7 g/day/kg BW) of EGCG. After 4 weeks of treatment, total cholesterol and low density lipoprotein plasma levels were significantly reduced in the group fed 1% EGCG when compared to the no treatment group. Plasma triglycerides and high-density lipoprotein levels did not change significantly. Following a single oral application of a liquid test-meal, intestinal cholesterol absorption in Wistar rats was 79.3% in the control group. In the group treated with 0.1 g/kg BW EGCG intestinal cholesterol absorption decreased to 73.7% and in the group treated with 0.5 g/kg BW of EGCG intestinal cholesterol absorption fell significantly to 62.7% (P = 0.005). Total fat absorption was very efficient in the control group (99.5% of the applied dose) and decreased significantly but moderately in the group treated with the highest doses of EGCG (0.75, 1 g/kg BW). In an in-vitro biliary micelle model, the addition of 55 microM to 1300 microM EGCG not only decreased cholesterol solubility dose-dependently in these micelles but also altered the size of the mixed lecithin/taurocholate/cholesterol micelles as demonstrated by light scattering. This study provides evidence suggesting that the cholesterol-lowering effect of green tea is mainly elicited by EGCG, one of the most abundant catechins contained in green tea. It is suggested that one of the underlying mechanisms by which EGCG affects lipid metabolism is by interfering with the micellar solubilization of cholesterol in the digestive tract, which then in turn decreased cholesterol absorption.