From her letter to the editor at American Family Physician:
A rigorously scientific analysis of all the green tea research can be best interpreted as telling us there is no good evidence to support its use for conditions such as cancer, weight loss, or cardiovascular disease. The Natural Medicines Comprehensive Database, a resource for evidence-based, clinical information on natural medicines, rates green tea as only “possibly effective.” This rating is below their ratings of “effective” and “probably effective.”3 It raises a number of concerns about safety and interactions with other drugs, laboratory tests, and diseases. Additional concerns are that the dosage from brewed tea is variable, and commercial green tea extracts are classified as “diet supplements” under the Diet Supplement Health and Education Act and are not regulated for safety, purity, and content. Contamination and inconsistency of such products is common. In my opinion, we should not recommend green tea to our patients unless more convincing evidence is found.
Source: More Evidence of Green Tea’s Effectiveness Is Needed – Letters to the Editor – American Family Physician