Mixed
Commercial green tea dietary supplements (GTDS) exhibit significant discrepancies between label claims and actual phytochemical content (caffeine, EGCG, total polyphenols), with actual levels frequently deviating by 43-182% from stated values.
Do not rely on the label of a green tea supplement to know exactly how much caffeine or EGCG you are consuming. This study found that actual content can be significantly higher or lower than what is printed on the bottle. If you are sensitive to caffeine or relying on specific polyphenol doses for health benefits, verify the product's quality through third-party testing or choose brands with transparent, verified manufacturing practices.
Actual caffeine levels varied from 43 to 182% of the label claims... The label claims of EGCG content in three of the GTDS corresponded to the actual amount... Six of the GTDS contained less than the claimed amount... Five of the 19 GTDS studied made claims about the amount of total tea polyphenols, which ranged from 14 to 36% of their label claims.
Why this rating
Direct chemical analysis (HPLC) of 19 commercial products provides robust, objective data, though the sample size is limited to specific brands.
Source
Catechin and Caffeine Content of Green Tea Dietary Supplements and Correlation with Antioxidant Capacity
Navindra P. Seeram et al. · Journal of Agricultural and Food Chemistry · 2006
DOI 10.1021/jf052857r
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