The ability of green tea to positively modulate key markers of gastrointestinal function in rats.

The beneficial effects of selenium-containing green tea (Se-GTE, 1.44 mg selenium/kg dry leaves) and China green tea (CH-GTE, 0.13 mg selenium/kg leaves) on the population size of lactobacilli and bifidobacteria and the activity of two microbial enzymes in the caeca of rats have been investigated. Oral gavage of rats with Se-GTE extract for 6 days resulted in a significant increase in caecal counts of lactobacilli and bifidobacteria (p < 0.05) while significantly reducing the caecal counts of bacteroides and clostridial bacteria. In contrast, gavaging the rats with CH-GTE extract for 6 days resulted in a slight but not significant increase in the numbers of caecal lactobacilli and bifidobacteria but decreased significantly the numbers of bacteroides (p < 0.05) and clostridia (p < 0.05). In addition, rats gavaged with CH-GTE and Se-GTE showed a 17.2% and 21.3% reduction in the activity of the bacterial enzyme β-glucuronidase, respectively, when compared with the rats gavaged with water only. β-glucuronidase is considered to be one of the enzymes that increases the risk for colorectal cancer. Moreover, gavaging rats with these teas resulted in 19% and 25.5% increments in the activity of β-glucosidase, respectively. In conclusion, Se-GTE showed both bifidogenic and lactogenic effects and the high level of selenium may be behind the superiority of this tea over CH-GTE.