Studie zur Vorbeugung von
Darmpolypen mit Grüntee-Extrakt

Dose determination

The application of green tea extract standardized to a twice daily dose of 150 mg EGCG was decided upon a review of the existing literature on clinical long-term prevention studies and the rationale that a nutriprevention study should involve doses corresponding to nutritional use of green tea for which there is at least some epidemiological evidence for a cancer-preventive action.

A simple calculation shows that a daily dose of 300 mg EGCG corresponds to a normal intake of green tea: one cup of green tea is brewed with approximately 2 g of tea leaves. Tea leaves have a catechin content of about 10%. If the tea is brewed for 10 min, about 80% of the catechins will have dissolved. The amount of EGCG is about 50% of the catechins. This means that one cup of this green tea would contain about 80 mg EGCG, and the same amount of other dissolved catechins. Thus, 300 mg would correspond to 4 cups of tea brewed with this method. In practice, tea may be brewed with a shorter duration, which would result in a lower concentration of catechins. Thus, the daily dose applied in this study certainly lies within the range of 4-7 cups of tea per day, which is still a physiological dose.

A check with the literature reveals that in all existing long term studies, similar doses have been given (see table table11).

Table 1

summary of long term (≥ 2 weeks) interventional studies with green tea extract

Study

Daily intake of EGCG

Duration of trial

Sample size

Total catechins

EGCG

ECG

EGC

EC

Caffeine

[38]

300 mg

12 months

60

76%

52%

6%

6%

12%

0.1%

[7]

350 mg

2 months

69

84%

Not specified

19%

[31]

800 mg

1 month

8

98%

70%

13%

11%

[9]

150 mg

12 months

71

20%

11%

2%

7%

0.2%

3%

[39]

225 mg

3 months

64

100%

35%

17%

< 1%

< 1%

7%

[40]

800 mg

1 month

26

80%-98%

50-75%

12%

2%

[6]

2000 mg

6 months

5

98%

70%

13%

11%

[2]

300 mg

2 weeks

42

100%

100%

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