Green tea extract may harm the liver in people with certain genetic variations

Despite offering protection against several diseases, it may cause liver damage.


The predominant catechin in green tea, epigallocatechin gallate (EGCG), may be hepatotoxic in high doses. A new study by Rutgers University investigated whether people with certain genetic variations were more likely than others 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).

Scientists found that green tea extract may harm the liver in people with certain genetic variations.

Hamed Samavat, a senior author of the study and an assistant professor of nutrition sciences at the Rutgers School of Health Professions, said, “Learning to predict who will suffer liver damage is potentially important because there’s growing evidence that high-dose green tea extract may have significant health benefits for those who can safely take it.”

For this study, scientists used data from the Minnesota Green Tea Trial, extensive research on green tea’s effect on breast cancer. They selected two genetic variations because each controls the synthesis of an enzyme that breaks EGCG down.

The Minnesota Green Tea Trial was chosen because it was a large, methodical research of an unique population. More than 1,000 postmenopausal women participated in the 12-month, placebo-controlled experiment, which gathered information at 3, 6, and 9 months.

Scientists showed that early signs of liver damage 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.

After nine months of taking the green tea supplement, participants’ levels of the enzyme that signals liver stress increased, on average, by nearly 80% in those with the high-risk UGT1A4 genotype and by 30% in those with low-risk genotypes.

Samavat said“We’re still a long way from being able to predict who can safely take high-dose green tea extract. The risk of liver toxicity is only associated with high levels of green tea supplements and not with drinking or even taking lower doses of green tea extract. Variations in this one genotype don’t completely explain the variations in liver enzyme changes among study participants. The full explanation probably includes several different genetic variations and a number of non-genetic factors.”

“Still, we do think we have identified an important piece of the puzzle and taken a step toward predicting who can safely enjoy any health benefits that high-dose green tea extract provides.”

Journal Reference:

  1. Laura Acosta, Laura Byham-Gray, Mindy Kurzer, Hamed Samavat. Hepatotoxicity with High-Dose Green Tea Extract: Effect of Catechol-O-Methyltransferase and Uridine 5’-Diphospho-glucuronosyltransferase 1A4 Genotypes. Journal of Dietary Supplements, 2022; 1 DOI: 10.1080/19390211.2022.2128501
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