Long-term use of a high-dose green tea extract may protect against cancer, cardiovascular disease, obesity, and type 2 diabetes, but may also create liver damage in some people.
A new study points to two genetic variants that predict who may be at risk.
“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,” says Hamed Samavat, an assistant professor of nutrition sciences at the Rutgers School of Health Professions and senior author of the study in the Journal of Dietary Supplements.
Using data from the Minnesota Green Tea Trial, a large study of green tea’s effect on breast cancer, the research team 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).
Researchers led by Laura Acosta, then a doctoral student and now a graduate, selected two genetic variations in question because each controls the synthesis of an enzyme that breaks EGCG down.
They selected the Minnesota Green Tea Trial because it was a large, well-designed study of a unique population. The year-long, placebo-controlled trial included more than 1,000 postmenopausal women and collected data at 3, 6, 9, and 12 months.
An analysis 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.
On average, participants with the high-risk UGT1A4 genotype saw the enzyme that indicates liver stress go up nearly 80% after nine months of consuming the green tea supplement, while those with low-risk genotypes saw the same enzyme go up 30%.
“We’re still a long way from being able to predict who can safely take high-dose green tea extract,” says Samavat, who notes the risk of liver toxicity 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.
“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.”
“Still,” Samavat continues, “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.”
Source: Rutgers University