The Safety of Green Tea Extract Supplementation in Postmenopausal Women at Risk for Breast Cancer: Results of the Minnesota Green Tea Trial

Abstract

The objective of this study was to monitor adverse events (AEs) in healthy postmenopausal women randomized to receive either green tea extract (GTE) containing 840 mg (‐)‐epigallocatechin‐3‐gallate (EGCG)/day (n=538) or placebo (n=537) for one year. Data on AEs was obtained by participant self‐report and hepatic panel assessment. AEs were recorded and graded using the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE), v.4.03. 407 participants in the GTE group reported 1141 AEs; 391 participants in the placebo group reported 1031 AEs. Infections and infestations were the most common AEs (139 GTE vs. 145 placebo participants, p = 0.67) followed by gastrointestinal (GI) disorders (137 GTE vs. 123 placebo participants, p = 0.33). Nausea incidence was higher in GTE participants (55 (10.2%) vs. 26 (4.8%), p < 0.001). Diarrhea incidence was lower in the GTE group (24 (4.5%) vs. 43 (8%) participants, p = 0.02). More participants taking GTE reported dermatologic AEs (18 (3.3%) vs. 8 (1.5%), p = 0.05). Alanine aminotransferase (ALT) elevations were seen in 36 (6.7%) GTE vs. 4 (0.7%) placebo participants (p < 0.001). Twenty‐six serious adverse events (CTCAE grades 3‐5) occurred in 12 GTE vs. 8 placebo participants (p = 0.37). GTE containing 840 mg EGCG/day was associated with mainly mild, transient AEs and was well tolerated by most participants, though an association with GI and hepatic abnormalities was confirmed. This project was supported by the NIH/NCI.