Before you begin reading further, let me clarify: green tea as a beverage is not the subject here. In fact, drinking green tea every day is a good health habit that provides antioxidants and immunity-boosting benefits.
But you might be surprised to know that health experts caution against taking supplements that contain green tea extracts, pointing out their potential to hurt the liver.
I was surprised to hear that haloed green tea could ever be associated with anything mildly unpleasant, let alone pose a risk to the health of the liver. But the truth is, several weight-loss supplements and energy drinks contain green tea extract, and a number of case studies have established that even minimal use of these unregulated dietary supplements can lead to liver failure, requiring liver transplant.
LiverTox, a joint information library run by the Liver Disease Research Branch of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and the Division of Specialized Information Services of the National Library of Medicine (NLM), National Institutes of Health, has this to say: “Green tea extract and concentrated infusions of green tea have been implicated in many cases of clinically apparent acute liver injury, including instances of acute liver failure and death.”
The source goes on to cite the case of a 37-year-old woman who was taking a weight loss supplement that had green tea extract as its major component. She developed nausea, abdominal pain and jaundice four months after starting the supplement.
In a New York Times article from last year, Anahad O’Connor interviews Dr. Herbert L. Bonkovsky, the director of the liver, digestive and metabolic disorders laboratory at Carolinas HealthCare System. The article explains that green tea extract contains catechins, “a group of potent antioxidants that reputedly increase metabolism. The extracts are often marketed as fat burners, and catechins are often added to weight-loss products and energy boosters. Most green tea pills are highly concentrated, containing many times the amount of catechins found in a single cup of green tea … In high doses, catechins can be toxic to the liver … and a small percentage of people appear to be particularly susceptible.”
Some important notes about this information:
- The Drug-Induced Liver Injury Network estimates that unregulated supplements now account for 20 percent of drug-related liver injuries.
- The catechin component of green tea has been identified as the culprit of hepatotoxicity. Approximately 10% of green tea extract is composed of catechins. Of these, one called EGCG is present in the highest concentration.
- There is great variability in the concentration of green tea extract, EGCG and other components among marketed products, which may explain while some products have been implicated in hepatotoxicity.
- Studies on rats have associated higher doses of green tea extract with higher risk of liver injury.
Should you stop drinking green tea, then? No. Just be cautious of weight-loss energy supplements and energy drinks, especially those with green tea extract.
Professor Peter O’Brian of the Leslie Dan Faculty of Pharmacy offers sound advice for those who might want to exploit the antioxidant and health promoting properties of tea polyphenols. “Don’t consume concentrated doses in pill form as this could create more health problems than it might fix.”