In a study from Rutgers University, scientists found long-term use of high-dose green tea extract may provide some protection against cancer, heart disease, obesity, and type 2 diabetes, but it also may create liver damage in a small minority of the population.
Who is at risk?
The study provides the first solid clue: two genetic variants that predict some of the risks.
In the study, the team used data from the Minnesota Green Tea Trial, a large study of green tea’s effect on breast cancer,
They examined 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 selected two genetic variations in question because each controls the synthesis of an enzyme that breaks EGCG down.
The year-long, placebo-controlled trial included more than 1,000 older women and collected data at 3, 6, 9, and 12 months.
They 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.
The team noted 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.
If you care about nutrition, please read studies about how the Mediterranean diet could protect your brain health and the best time to take vitamins to prevent heart disease.
For more information about nutrition, please see recent studies that olive oil may help you live longer, and vitamin D could help lower the risk of autoimmune diseases.
The study was conducted by Hamed Samavat et al and published in The Journal of Dietary Supplements.
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