Evaluation of cost versus antioxidant determinants in green tea dietary supplements.

OBJECTIVE: To investigate the association between cost and (a) chemical constituents and (b) antioxidant activity as quality determinants of select green tea supplements available in the United States.

DESIGN/SETTING: Laboratory analysis of green tea using HPLC and antioxidant assay methods.

MAIN OUTCOME MEASURES: Correlation between selected quality parameters and daily cost based on the serving size as stated in the label. Quality was defined in terms of (a) catechin levels (validated high-performance liquid chromatography method), (b) total phenolic content (Folin-Ciocalteu method), and (c) antioxidant activity (total antioxidant capacity and diphenylpicryl hydrazyl free-radical scavenging).

RESULTS: A wide range of variation in marker levels and antioxidant activity was observed in the evaluated products. Catechin levels correlated well with the total phenolic content in each product while antioxidant activities were not as consistent when correlated with catechin/polyphenol levels. There was also a low correlation between product cost and quality.

CONCLUSION: Our results indicate that product cost does not always reflect quality, at least within the selected range of products. Thus, for a pharmacist to be able to recommend quality green tea dietary supplements, factors other than cost should be considered.