Tea Polyphenols - Antioxidants or Prebiotics?

[Guest guest]

Blank

Tea Polyphenols - Antioxidants or Prebiotics?

by ls*

ImmuneSupport.com

01-03-2007

The 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 antioxidant 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 [normal] bacteria, including probiotics, and

could therefore be considered as prebiotics.” [Probiotics are bacteria

beneficial for healthy intestinal function, and prebiotics promote the growth of

probiotics.]

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.

n Green tea contains between 30 and 40 percent water-extractable polyphenols,

n While black tea (green tea that has been oxidized by fermentation) contains

between 3 and 10 percent,

n And Oolong tea is semi-fermented tea, and is somewhere between green and black

tea.

The four primary polyphenols found in fresh tea leaves are epigallocatechin

gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.

The new study, published in the [November 2006 issue of] the 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:

n Strains of the aerobic pathogens E. coli, Salmonella, and Listeria,

n Probiotic Lactobacillus strains,

n Strains of the anaerobic pathogens Bacteroides and Clostridium,

n And probiotic Bifidobacterium strains.

Cells were cultured in the presence of 0.1 percent 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 pathogenic 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. And, “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.

______

* This article is reproduced with permission of DecisionNewsMedia

www.decisionnewsmedia.com, which published it online December 20, 2006.

Copyright 2006 DecisionNewsMedia.

** “Effect of tea phenolics and their aromatic fecal bacterial metabolites on

intestinal microbiota,” by H.C. Lee, A.M. Jenner, C.S. Low, and Y. K. Lee.

Published in the November 2006 issue of the journal Research in Microbiology,

volume 157, issue 9, pages 876-884. The researchers are affiliated with the

Departments of Microbiology and Biochemistry, National University of Singapore,

Republic of Singapore.

http://www.immunesupport.com/library/print.cfm?ID=7619 & t=CFIDS_FM