Studie zur Vorbeugung von
Darmpolypen mit Grüntee-Extrakt

Discussion

The aim of this large prevention trial is to study the influence of regular nutritional supplementation with green tea extract containing EGCG, one of the active components of green tea, on the incidences of metachronous colorectal adenomas in subjects who have undergone polypectomy. Thus, it is a secondary prevention trial

The limitation of prior large-scale chemoprevention trials, when administering drugs like ASS or COX-2 inhibitors to a large group of healthy individuals for long term treatment, was safety. Even if the trials were successful with respect to their primary endpoint, prevention of metachronous colorectal adenomas, the clinical utility of NSAIDs used for this indication is rather low due to the unwanted side effects of these drugs.

This is the first large-scale controlled prevention trial using nutritional supplement as the active principle. The dose of ECGC in our green tea extract was chosen to mimic high and regular green tea consumption without the influence of caffeine. While we are aware that 300 mg ECGC per day is lower than the dose range in some trials (with multiple dose data of up to 800 mg per day), we chose this dose because it corresponds to a somewhat physiological intake of green tea of about 4-7 cups per day, and because this dose is intended for use over an extended period of time, i.e. three years.

Of course, the mere act of taking a capsule two times a day might discourage some individuals from performing an individual preventive plan, but in principle this would be possible, and could be a recommendation for a broader target audience.

There are some data indicating that the other polyphenols in green tea may also contribute to its beneficial effects. Therefore we chose to use green tea extract containing a defined amount of ECGC but also the other polyphenols that are found in green tea.

We believe that a randomized controlled trial design is the only appropriate method to perform such a preventive trial, and justifies the efforts of such a trial. The limitations of the trial are the relatively short time period for follow-up (three years is short compared to the adenoma carcinoma sequence), the lack of a regular adherence measurement (ECGC does not accumulate and has a short half life, and therefore there is no long term parameter for the intake of EGCG), and the risk of a higher than presumed drop-out rate. However, the beneficial safety profile of green tea extract, and the widespread evidence on its cancer preventive potential, justifies in our view a validation of this compound for the nutriprevention of colorectal adenoma. Good accessibility and low costs might render this neutraceutical a top candidate for a wider use as food supplement in colon cancer prevention.

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