Camellia sinensis (green tea) was shown to inhibit low-density lipoprotein (LDL) oxidation, platelet aggregation and matrix metalloproteinases (MMPs) activities in vitro. Japanese researchers tried to elucidate whether or not C. sinensis consumption may have these effects in vivo, and therefore may be protective against atherosclerotic disease. They measured serum malondialdehyde-modified LDL (MDA-LDL) concentrations and urine 8-epi-prostaglandin (PG) F(2alpha) in 22 healthy male non-smokers who drank 7 cups/day of water for 2 weeks then drank 7 cups/day of green tea for the next 2 weeks. Regarding platelet aggregation, plasma thromboxane B(2) [TXB(2)] and 6-keto-PGF(1alpha) concentrations and ex vivo platelet aggregation were evaluated. Plasma MMP-2 and -9 concentrations were also measured. Of the 22 subjects, 20 had been in the habit of drinking green tea before the study. Plasma catechin concentrations significantly decreased at the end of the water period and then increased at the end of the green tea period. Although no change in plasma LDL-cholesterol concentrations was found, MDA-LDL concentrations and the ratio of MDA-LDL/LDL-cholesterol significantly decreased at the end of the green tea period. However, no significant changes were observed in urine 8-epi-PGF(2alpha) concentrations, platelet aggregation or plasma TXB(2), 6-keto-PGF(1alpha) or MMP concentrations.