Green Tea Extract: Clinical Uses and Evidence-Based Recommendations

Introduction to Green Tea Extract

The American College of Chest Physicians notes that green tea extract is currently under evaluation in phase 2 randomized controlled trials for lung cancer chemoprevention, but remains investigational and should not be used outside clinical trials 1, 2.
Animal studies show green tea extract inhibits lung tumor development in mice treated with tobacco-specific carcinogens, and epigallocatechin-3-gallate (EGCG) inhibits lung cancer in murine xenografts 1, 2.

The Mayo Clinic Proceedings recommends that green tea extract may be continued until surgery, unlike black tea extract which should be held for 2 weeks, due to the beneficial effects of catechins on diastolic cardiac function outweighing theoretical bleeding risk 3.

The American Academy of Ophthalmology notes that green tea extract cannot be recommended for computer vision syndrome, as studies comparing green tea extracts to placebo showed no difference in visual fatigue scores, critical flicker-fusion frequency, or amplitude of accommodation 4.

The American Heart Association states that water remains the preferred rehydration option, as green tea offers no clinical advantage, and very low-quality evidence from one RCT showed green tea-based 4.2% carbohydrate-electrolyte solution was associated with slightly increased mean glucose at 2 hours compared to water, with no other benefits 5, 6, 7.

The American Cancer Society recommends that green tea extract should not be recommended during active cancer treatment, as a clinical trial in prostate cancer survivors showed not only lack of benefit but increased nausea and diarrhea 8.