While the findings have not been confirmed in humans, they do support previous animal research showing that the polyphenols protected the liver from damage. Continuing research supports green tea's reputation as a disease-fighter and will help companies marketing the extract as a health supplement.
In the US green tea catechins are booming in weight loss products as the removal of ephedra from the market leaves a gap for thermogenic products. "Sales have more than quadrupled in the last two years," Scott Smith, vice president of Taiyo International, told NutraIngredients.com recently.
Pure ECEG (epigallocatechin gallate) extract, the major polyphenol in green tea and used in much of the research, is not yet available in Europe but the beverage is becoming fashionable, boosted by the wealth of research on green tea and the shift in sales in recent years to flavoursome or healthy alternative teas. According to market analysts Datamonitor, green tea consumption in 2002 was more than 20 times the 1997 figure.
In the new study, a team from the University of Hong Kong examined the effect of EGCG on mice treated with carbon tetrachloride, a model of liver injury.
Two different doses of EGCG were tested on measures of free radical production and increases in lipid peroxidation and compared with a control group.
The EGCG administration led to a dose-dependent decrease in all of the variables of liver injury observed in the carbon tetrachloride-treated mice, write the researchers in this month's American Journal of Clinical Nutrition (vol 80, no 3, pp742-751).
"Green tea polyphenols can be a useful supplement in the treatment of liver disease and should be considered for liver conditions in which proinflammatory and oxidant stress responses are dominant," they concluded.
Scientists at the University of North Carolina at Chapel Hill previously found that green tea extract increased the survival of fatty rat livers, damaged by alcohol exposure. They proposed that the extract could be used to help prevent liver transplant damage and failure.
Deaths from liver disease are soaring due to increasing cases of hepatits C. Hepatitis C, a blood-borne viral disease, is estimated to affect about 170 million people worldwide, and about five million in Europe. In about a third of all cases, the disease leads to a chronic infection that can cause fatal liver disease.