Green tea extract may cause damage to the liver in people with certain genetic variants

Long-term use of high-dose green tea extract may have some protective effects against cancer, cardiovascular disease, obesity, and type 2 diabetes, but it may also cause liver damage
to a small percentage of the population.

Who is at risk? A Rutgers study published in the Journal of Dietary Supplements provides the first reliable clue: two genetic variants
that predict some risk.

Hamed Samavat, senior author of the study and assistant professor of nutritional sciences at the Rutgers School of Health Professions, said: "Learning to predict who will suffer liver damage may be important as there is growing evidence that high-dose green tea extract may have significant health benefits
for those who can safely take it.
"

Using data from the Minnesota Green Tea Trial, a large study on the effects of green tea on breast cancer, the team investigated whether people with certain genetic variants were more likely than others to show signs of liver stress after consuming 843 mg of
the main antioxidant in green tea per day, a catechin called epigallocatechin gallate (EGCG).

The researchers, led by Laura Acosta, chose two problematic genetic variants because each controls the synthesis
of an enzyme that breaks down EGCG.
They chose the Minnesota Green Tea Trial because it was a large-scale, well-designed study
of a unique population.
The one-year placebo-controlled trial included more than 1,000 postmenopausal women and collected data
for 3, 6, 9 and 12 months.

An analysis by the researchers showed that signs of early liver damage were more common than normal in women with catechol-o-methyltransferase (COMT) genotype variation, and that uridine 5'-bisphosphoglucuronosyltransferase 1A4 (UGT1A4) genotype variation strongly predicted early signs
of liver damage.

On average, 9 months after ingesting green tea supplements, participants with the high-risk UGT1A4 genotype found an increase of nearly 80 percent in the enzyme indicating liver stress, while those with a low-risk genotype saw a 30 percent
rise in the same enzyme.

"We are still a long way from predicting who can safely take high-dose green tea extract
," Samavat said.
He noted that the risk of liver toxicity was only associated with high-dose green tea supplements, not with drinking green tea or taking low-dose green tea extract
.
"This variation in genotype does not fully explain the variation
in liver enzyme changes in study participants.
The full explanation may include many different genetic variants and may also include many non-genetic factors
.
”

"Nevertheless," Samawaat continued, "we do think we have found an important mystery and taken a step
forward in predicting who can safely enjoy any of the health benefits provided by high-dose green tea extract.
" ”