Green Tea Extract: Landmark Study on Pros and Cons

A Rutgers School of Health Professions study has claimed that long-term use of high-dose green tea extract may create liver damage in a small minority, notwithstanding the evidence of protection it offers against cancer, cardiovascular disease, obesity and type 2 diabetes. The study used data from the Minnesota Green Tea Trial to find whether people with certain genetic variations were more likely to show signs of liver stress after a year of ingesting 843 milligrams per day of the predominant antioxidant in green tea, a catechin called epigallocatechin gallate (EGCG). 

The authors contend that early signs of liver damage from high-dose green tea extract were somewhat more common than normal in women with one variation in the catechol-O-methyltransferase (COMT) genotype and strongly predicted by a variation in the uridine 5'-diphospho-glucuronosyltransferase 1A4 (UGT1A4) genotype. 

The risk of liver toxicity, the study authors highlight, is only associated with high levels of green tea supplements and not with drinking green tea or even taking lower doses of green tea extract. This pioneering study has indeed paved the way for deeper research towards identifying which patient groups can safely derive various health benefits of high-dose green tea extract devoid of the risk of liver damage.

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