Polyphenols in tea may preferentially suppress the growth of pathogenic
bacteria in the gut, but not the growth of 'friendly' bacteria, says a
new study from Singapore.

“It is generally believed that possible beneficial health effects of
tea polyphenols are due to their anti-oxidant activity,” wrote lead
author Hui Cheng Lee from the National University of Singapore.
“Evidence from our study indicates that phenolics are likely to
benefit the host by inhibiting pathogen growth and regulating commensal
bacteria, including probiotics, and could therefore be considers as
prebiotics.”

The health benefits of tea ranging from a lower risk of certain cancers
to weight loss, and protection against Alzheimer's, have been linked to
the polyphenol content of the tea. Green tea contains between 30 and 40
per cent of water-extractable polyphenols, while black tea (green tea
that has been oxidized by fermentation) contains between 3 and 10 per
cent. Oolong tea is semi-fermented tea and is somewhere between green
and black tea.

The four primary polyphenols found in fresh tealeaves are
epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate,
and epicatechin.

The new study, published in the Elsevier journal Research in
Microbiology, looked at the effects of 31 different phenolics extracted
from Yunnan Chinese tea on the growth of 28 different bacteria,
including pathogenic, commensal (normal), and probiotics found in the
intestine. These included strains of the aerobic pathogens E. coli,
Salmonella, and Listeria, and probiotic Lactobacillus strains, and
strains of the anaerobic pathogens Bacteroides and Clostridium, and
probiotic Bifidobacterium strains.

Cells were cultured in the presence of 0.1 per cent polyphenols at 37
degrees Celsius for 24 hours.

“Our data demonstrate that phenolic compounds have general inhibitory
effects on intestinal bacteria. The level of inhibition varies
depending on the bacterial species and chemical structure of the
compound,” wrote Lee.

Indeed, growth of the pathogenic E. coli and Salmonella typhimurium
were most strongly inhibited by the tea polyphenols and their
metabolites, as were strains belonging to the Bacteroides and
Clostridium genera.

However, the researchers report that the growth of the probiotic
Bifidobacterium and Lactobacillus strains were less affected by the tea
compounds.

“Since probiotic growth was relatively unaffected by most of the
aromatic compounds tested, probiotic colonization in the intestine
should continue in the presence of phenolics so as to improve the
intestinal microbial balance and inhibit pathogen growth,” said the
researchers.

“Although not fully comprehensive, this in vitro study indicates a
substantial number of complex interactions between intestinal bacteria,
phenolics and their metabolism,” they said.

They called for more research to further investigate the influence of
the tea polyphenols on gut microflora, and the overall maintenance of
human health and disease prevention, and said that the research
suggests that the antioxidants may also be prebiotic.

Prebiotic ingredients, or those that boost the growth of beneficial
probiotic bacteria in the gut, are worth about €90 million in the
European marketplace but are forecast to reach €179.7 million by
2010, according to Frost & Sullivan.

The market has been largely created by three inulin producers, all
based in Europe, but other ingredient manufacturers are increasingly
looking to promote the prebiotic effect of their products as evidence
suggests that prebiotics could be even more useful than the probiotic
bacteria that they feed.

Source: Research in Microbiology
2006, Volume 157, Pages 876-884
“Effect of tea phenolics and their aromatic fecal bacterial
metabolites on intestinal microbiota”
Authors: H.C. Lee, A.M. Jenner, C.S. Low, Y. K. Lee

The original story may be found at:

http://www.nutraingredients-usa.com/news/ng.asp?n=72941-tea-polyphenols-prebiotics