According to a recent Rutgers research, published in The Journal of Dietary Supplements, green tea extract may cause liver damage in a small percentage of people. The study suggests that there are two genetic variations that predict certain side effects. Hamed Samavat, 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."
To conduct the study of green tea's impact on breast cancer, data from the Minnesota Green Tea Trial was used. The researchers wanted to check if people with specific genetic variations were at a greater risk than others to show early signs of liver damage after consuming 843 milligrammes per day of the primary antioxidant extract of green tea, which is a catechin named epigallocatechin gallate (EGCG).
The researchers conducted an analysis which showed that early warning signs of liver damage were more common in women with a variation in the catechol-O-methyltransferase (COMT) genotype and strongly predicted by a variation in the uridine 5'-diphospho-glucuronosyltransferase 1A4 (UGT1A4) genotype. On an average, people who were at a high-risk UGT1A4 genotype saw the enzyme that is an indication of liver stress spikes by around 80 percent after nine months of having the green tea antioxidant, and the people who had low-risk genotypes saw that the same enzyme can go up by 30 percent.
Samavat further added, "We're still a long way from being able to predict who can safely take high-dose 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 a number of different genetic variations and probably a number of non-genetic factors. 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."