Long-term use of high-dose green tea extract may provide some protection against cancer, cardiovascular disease, obesity, and type 2 diabetes, but it can also result in liver damage in a small minority of the population.
Who is at risk? Rutgers research published in The Journal of Dietary Supplementsprovides the first solid clue: two genetic variants that predict part of the risk.
“Learning to predict who will experience liver damage is potentially important as there is mounting evidence that high-dose green tea extract can have significant health benefits for those who can safely ingest it,” said Hamed Samavat, senior author of the Study and Assistant Professor of Nutrition Science at Rutgers School of Health Professions.
Using data from the Minnesota Green Tea Trial, a large study of green tea’s effect on breast cancer, the research team looked at whether people with certain genetic variations were more likely than others to show signs of liver stress after a year of ingesting 843 milligrams a day the predominant antioxidant in green tea, a catechin called epigallocatechin gallate (EGCG).
Researchers led by Laura Acosta, then a graduate student, now a graduate student, selected two genetic variations in question because each directs the synthesis of an enzyme that breaks down EGCG. They chose the green tea study in Minnesota because it was a large, well-designed study with a unique population. The year-long, placebo-controlled study enrolled more than 1,000 postmenopausal women and collected data at 3, 6, 9 and 12 months.
An analysis by researchers showed that early signs of liver damage occurred slightly more frequently than normal in women with a variation in the catechol-O-methyltransferase (COMT) genotype and were strongly influenced by a variation in uridine-5′-diphospho-glucuronosyltransferase 1A4 (UGT1A4 )-Genotype.
On average, participants with the high-risk UGT1A4 genotype saw the enzyme that indicates liver stress increase by almost 80 percent after nine months of consuming the green tea supplement, while participants with low-risk genotypes saw the same enzyme increase by 30 percent percent increase.
“We’re still a long way from predicting who can safely ingest high-dose green tea extract,” said Samavat, who noted that the risk of liver toxicity is only associated with high amounts of green tea supplements and not green tea drinking is tea or even taking lower doses of green tea extract. “Variations in this one genotype do not fully explain the variations in liver enzyme changes in study participants. The full explanation likely involves a number of different genetic variations and likely a number of non-genetic factors.”
“Nevertheless,” Samavat continued, “we believe we’ve identified an important piece of the puzzle and taken a step toward predicting who can safely enjoy the health benefits of a high-dose green tea extract.”
Materials provided by Rutgers University. Originally written by Andrew Smith. Note: Content can be edited for style and length.