Tuesday July 22, 2014 (foodconsumer.org) -- A case report (1) suggests that taking a high dose of green tea extract, which is commonly used by some patients to fight cancer and promote weight loss, can result in liver injury, which can be naturally reversed by discontinuing the supplementation though.

According to the report, a 63-year old woman took green tea capsules as recommended by a cancer support group.  As a result, she developed acute drug induced hepatitis.  It was not clear whether she used a mega- or high dose of green tea extract and how long she took the supplement while it was certain that she had medical conditions.

The patient discontinued taking green tea capsules and she was able to completely reverse the side effect.  The doctors characterized green tea extract as a probable cause for the acute drug induced hepatitis.

Laboratory tests revealed that the green tea capsules did not seem to contain any contaminants and it mainly contained two typical ingredients found in green tea, (-)-epigallocatechin-3-O-gallate (EGCG, 93.2%) and epicatechin (EC, 6.8%).

The report suggests that green tea extract supplements may pose a risk in some patients who have underlying conditions and are susceptible to the toxicity of green tea extract when taken in high doses.

High doses of green tea extract exhibit oxidant properties, which are needed to fight cancer.  Research conducted at Rutgers University and other organizations shows that EGCG can promote apoptosis and kill cancerous cells.  Like many cancer drugs, it is not surprising that green tea extract may too result in side effects.

The case report suggests that consumers should be aware that supplements, particularly those pure compounds when used in high doses may cause side effects in some users and users should keep an eye on potential side effects or adverse effects and seek medical attention once they experience anything unexpected.

A study (2) recently published in the Canadian Journal of Physiology and Pharmacology suggests that EGCG at a concentration of 10 μmol/L was toxic for hepatocytes in rats that received partial hepatectomy or sham surgery.  

The study was conducted on isolated cells and the results may not be applicable to in vivo cells though.  And humans are expected to tolerate much higher doses.

Another study (3) recently released in British Journal of Nutrition suggests that taking EGCG in a dose of 300 mg per day for 12 weeks did not result in any side effects in obese women.

Overall, the toxicity of green tea extract as a chemo-preventative or alternative treatment is well tolerated when the dose is adequate and the cases of side effects are rarely reported.  (David Liu, PHD)

References:

1, Pillukat MH, Bester C, Hensel A, Lechtenberg M, Petereit F, Beckebaum S, Müller KM, Schmidt HH.  Concentrated green tea extract induces severe acute hepatitis in a 63-year-old woman - A case report with pharmaceutical analysis.  J Ethnopharmacol. 2014 May 24.

2, Mezera V1, Kucera O, Moravcova A, Peterova E, Cervinkova Z.  The effect of epigallocatechin gallate on hepatocytes isolated from normal and partially hepatectomized rats.  Can J Physiol Pharmacol. 2014 Jun;92(6):512-7.  

3, Mielgo-Ayuso J, Barrenechea L, Alcorta P, Larrarte E, Margareto J, Labayen I.  Effects of dietary supplementation with epigallocatechin-3-gallate on weight loss, energy homeostasis, cardiometabolic risk factors and liver function in obese women: randomised, double-blind, placebo-controlled clinical trial.  Br J Nutr. 2014 Apr 14;111(7):1263-71.