One of the amazing effects of tea polyphenols is their ability to destroy pathogenic (disease-causing) bacteria like E. coli, Salmonella, Staphylococcus aureus and Clostridium inside the body, particularly in the digestive tract. But if tea polyphenols are strong enough to kill major pathogens, do they also kill the “friendly” bacteria in your intestinal tract – the ones you need to digest and absorb your food properly?
To find out, scientists from the National University of Singapore looked at the effects of different tea polyphenols extracted from Yunnan Chinese tea on the growth of 28 kinds of bacteria, both “friendly” and pathogenic, found in the intestines.
As expected, the polyphenols inhibited the growth of pathogenic bacteria, especially Clostridium perfringens (a common cause of food poisoning), Clostridium difficile (linked to colitis), and Bacteroides (a cause of abscesses if the bacteria manage to escape from the intestines). However the gut’s “friendly” bacteria, including Bifidobacterium and Lactobacillus, were relatively unaffected by the tea polyphenols.
In short, tea was able to increase the "friendly" bacteria while decreasing the "unfriendly" bacteria, thus changing the balance of bacteria in the gut for the better.
(Lee HC, Jenner AM, Low CS, Lee YK. Effect of tea phenolics and their aromatic fecal bacterial metabolites on intestinal microbiota. Research in Microbiology 2006;157(9):876-84.