There has been a long history of promoting green tea as a health drink that aids weight loss, millions of people drink green tea every day to lose belly fat, but it still has its share of side effects.

According to Laura Acosta, in high doses, epigallocatechin gallate (EGCG) ‘s predominant catechin in green tea may be hepatotoxic. 

As one of the most vital metabolic organs in the body, the liver synthesizes and degrades a wide variety of critical biological molecules, including carbohydrates, proteins, and lipids. There has also been a growing disease burden from liver diseases in recent decades, including hepatotoxicity, fatty liver, and cirrhosis. 

Among the three leading causes of cancer-related deaths worldwide are primary hepatic malignancies, of which HCC is the most prevalent, accounting for the most significant number of deaths.

History of Green Tea Effects 

Green tea supplements have been recalled for the dangers of higher dose pills after a man was rushed for a liver transplant. A BBC report (October 25th, 2018) reported that Jim McCants took green tea capsules for just a few months before he suffered severe liver damage and was rushed to the hospital for an urgent liver transplant. After four years, he still suffers chronic abdominal pain.

Dr. Laura Wyness, a nutritionist, responded to the report by saying that green tea supplements contain high levels of antioxidants that are harmful to our health.

” Green tea is less processed than black tea and therefore contains more flavonoids such as catechins and epigallocatechin gallate ( EGCG ) which are strong antioxidants. “

Dr. Laura Wyness

After reports of liver damage, the Norwegian food safety authority Mattilsynet warned against green tea extract supplements in 2016. As a result of the high levels of the active compound EGCG (epigallocatechin – 3 – gallate) in the products, the authority noted a higher level of EGCG than what could be obtained from simply drinking green tea.

It was concluded earlier in 2018 by the European Food Safety Authority ( EFSA) that, while green tea catechin intake is generally safe from infusions of green tea, supplementation with doses greater than 800 mg of EGCG per day can result in liver damage.

What Did The Study Reveal?

In high doses, epigallocatechin gallate (EGCG), the predominant catechin in green tea, may be hepatotoxic. Therefore, the study aimed to find out if the genotypes of catechol-O-methyltransferase (COMT) and uridine 5′-diphospho-glucuronosyltransferase 1A4 (UGT1A4) affected liver injury biomarkers following long-term, high-dose green tea extract (GTE) supplementation in postmenopausal women. 

In a secondary analysis, participants in the Minnesota Green Tea Trial (N = 1,075) were randomized to consume high-dose green tea extract (843 mg/day EGCG) or placebo capsules for 12 months. 

The study examined changes in aspartate aminotransferase (AST), alanine aminotransferase (ALT), AST: ALT ratio, and alkaline phosphatase over time, adjusting for potential confounders across the COMT and UGT1A4 genotypes.

Among the GTE group (n = 400), the mean age and BMI were 59.8 years and 25.1 kg/m2, respectively, and 98% of the subjects were white. From baseline to month 3, the mean AST: ALT ratio changed by 1.0% in the COMT (rs4680) A/G genotype versus 4.8% in the A/A genotype (p = 0.03). 

Mean ALT changes were +78.1% and +82.1% from baseline to months 6 and 9 for A/C genotypes of UGT1A4 (rs6755571), respectively, versus +28.0% and +30.1% for C/C genotypes (p = 0.001 and p = 0.004).

Results of the Study

After 6-9 months of high-dose GTE supplementation among postmenopausal women, the UGT1A4 A/C genotype may be associated with clinically significant serum transaminase elevations. A genetically-informed paradigm for the therapeutic use of GTE may be possible if we understand the genetic underpinnings of GTE-related hepatotoxicity.  

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