There is good evidence from in vitro studies that
green tea catechins have a role in protection against degenerative diseases. However, the concentrations used in vitro are often higher than those found in animal or human plasma, and so in vivo evidence is required to demonstrate any protective effect of catechins. This article summarizes the most interesting in vivo animal studies on the protective effects of
green tea catechins against
biomarkers for
cancer,
cardiovascular disease, and other degenerative diseases. Generally, most studies using animal models show that consumption of
green tea (catechins) provides some protection, although most studies have not examined dose response.
Tea catechins could act as antitumorigenic agents and as immune modulators in immunodysfunction caused by transplanted
tumors or by
carcinogen treatment.
Green tea has antiproliferative activity in
hepatoma cells and hypolipidemic activity in
hepatoma-treated rats, and some studies report that it prevents hepatoxicity. It could act as a preventive agent against
mammary cancer postinitiation. Nevertheless, the implications of
green tea catechins in preventing
metastasis have not been clearly established. Long-term feeding of
tea catechins could be beneficial for the suppression of high-fat diet-induced
obesity by modulating lipid metabolism, could have a beneficial effect against
lipid and
glucose metabolism disorders implicated in
type 2 diabetes, and could also reduce the risk of
coronary disease. Further investigations on mechanisms, the nature of the active compounds, and appropriate dose levels are needed.