Tea (Camellia sinensis) is one of the most consumed beverages in the world and has been suggested to reduce the risk of many chronic diseases.
One of the active ingredients in green tea is EGCG (epigallocatechin-3-gallate) which is found in tea and is found in green tea dietary supplements.
We have written previously about clinical trials with green tea and you can read those here.
A clinical trial was published with green tea in the journal of Cancer, Epidemiology and Biomakers Prevention. 
The purpose of this clinical trial was to determine if high dose green tea will lead to drug interactions.
Here are the details of the study
– 42 human subjects were enrolled in this 4 week study
– Patients were given low dose drugs known to be metabolized by the liver enzymes CYP1A2, CYP2D6, CYP2C9, and CYP3A4 (i.e. cytochrome P450 enzymes). Blood levels were measured on Day 1 and Day 28
– Dose: Each patient was administered a total of 800 mg of EGCG daily. The product was Polyphenon E which contains 80 to 98% total cateechins with EGCG approximatley 50 to 75% in each capsule.
Here are the main results
– Four weeks of green tea catechin intervention did not alter the phenotypic indices of CYP1A2, CYP2D6, and CYP2C9, but resulted in a 20% increase (P = 0.01) in the area under the plasma buspirone concentration-time profile, suggesting a small reduction in CYP3A4 activity.
Here are more results of clinical research with green tea.
Here is what the authors had to say
We conclude that repeated green tea catechin administration had no effects on CYP1A2, CYP2D6, and CYP2C9 activities but seemed to result in a small reduction in CYP3A4 activity.
and
These results suggest that green tea catechin administration is not likely to result in clinically significant effects on the disposition of drugs metabolized by CYP enzymes.
Take away message
Drugs are metabolized by a group of enzymes called cytochrome P450 enzymes that include CYP1A2, CYP2D6, CYP2C9, CYP3A4 and several others.
Drug interactions are a serious concern when it comes to dietary supplements, however, the results of this study suggest that green tea has a low risk of drug interactions.
You should always error on the side of caution and discuss with your doctor or pharmacist to determine if there are concerns for drug interactions with green tea supplements.
Reference
Chow et al. Cancer Epidemiololgy, Biomarkers and Prevention. 2006; Volume 15 (Issue 12): Pages 2473-6.
His research on plant medicine has led to more than 45 publications and abstracts.This research has been presented at international meetings in the USA, France, Turkey, Peru, Israel, Austria, and Italy.
Categories: Antioxidant, Ask the Pharmacist, Clinical Trials, Dietary Supplements