Abstract
There remain liver-related safety concerns, regarding potential hepatotoxicity in humans, induced by green tea intake, despite being supposedly beneficial. Although many randomized controlled trials (RCTs) of green tea extracts have been reported in the literature, the systematic reviews published to date were only based on subjective assessment of case reports. To more objectively examine the liver-related safety of green tea intake, we conducted a systematic review of published RCTs. A systematic literature search was conducted using three databases (PubMed, EMBASE and Cochrane Central Register of Controlled Trials) in December 2013 to identify RCTs of green tea extracts. Data on liver-related adverse events, including laboratory test abnormalities, were abstracted from the identified articles. Methodological quality of RCTs was assessed. After excluding duplicates, 561 titles and abstracts and 119 full-text articles were screened, and finally 34 trials were identified. Of these, liver-related adverse events were reported in four trials; these adverse events involved seven subjects (eight events) in the green tea intervention group and one subject (one event) in the control group. The summary odds ratio, estimated using a meta-analysis method for sparse event data, for intervention compared with placebo was 2.1 (95% confidence interval: 0.5–9.8). The few events reported in both groups were elevations of liver enzymes. Most were mild, and no serious liver-related adverse events were reported. Results of this review, although not conclusive, suggest that liver-related adverse events after intake of green tea extracts are expected to be rare.
Highlights
Green tea is widely consumed in Asia, especially in Japan and China.[1]
In order to more objectively examine the safety of green tea intake, we conducted a systematic review and collected data on liver-related adverse events reported in randomized controlled trials (RCTs) with a green tea intervention
Articles on RCTs with oral intake of green tea were collected according to the following inclusion criteria: original articles; studies with human subjects; written in English; green tea alone orally administered in the intervention group; studies with concurrent ‘placebo’ or ‘no-treatment’ controls; and reports of adverse events
Summary
Green tea is widely consumed in Asia, especially in Japan and China.[1]. It has been a popular drink for a long time and is consumed by many people on a daily basis. Consecutive cases of liver damage seemingly caused by excessive consumption of green tea supplements have been reported, and this has become a safety concern. In order to investigate the hepatic safety of green tea extracts in humans, Sarma et al.[3] conducted a systematic review of case reports published from 1966 to 2007. In another review of case reports published from 1999 to 2008, including two unpublished reports,[9] a total of 36 cases of liver damage were reported, including 13 cases of duplication with Sarma et al.[3] This review concluded that, a causal relationship to green tea extracts was suggested, the effects of concomitant drugs were not ruled out. There are several case reports that suggested high doses of green tea extracts or catechin as a cause of liver damage, a relationship could not. To the best of our knowledge, the systematic reviews published to date were only based on subjective assessments of case reports.[3,9] In order to more objectively examine the safety of green tea intake, we conducted a systematic review and collected data on liver-related adverse events reported in RCTs with a green tea intervention
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