Protective role of probiotics and prebiotics in colon cancer123

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ABSTRACT

Ingestion of viable probiotics or prebiotics is associated with anticarcinogenic effects, one mechanism of which is the detoxification of genotoxins in the gut. This mechanism was shown experimentally in animals with use of the rat colon carcinogen 1,2-dimethylhydrazine and by determining endpoints that range from tumorigenesis to induction of DNA damage. Because of the complexity of cancer initiation, cancer progression, and the exposure of cancer in the gut, many types of interactions may be envisaged. Notably, some of our newer studies showed that short-lived metabolite mixtures isolated from milk that was fermented with strains of Lactobacillus bulgaricus and Streptococcus thermophilus are more effective in deactivating etiologic risk factors of colon carcinogenesis than are cellular components of microorganisms. Ingestion of prebiotics results in a different spectrum of fermentation products, including the production of high concentrations of short-chain fatty acids. Gut flora, especially after the ingestion of resistant starch, induces the chemopreventive enzyme glutathione transferase π in the colon of the rat. Together, these factors lead to a reduced load of genotoxic agents in the gut and to an increased production of agents that deactivate toxic components. Butyrate is one such protective agent and is associated with lowering cancer risk. It was recently shown that buytrate may inhibit the genotoxic activity of nitrosamides and hydrogen peroxide in human colon cells. In humans, the ingestion of probiotics leads to the excretion of urine with low concentrations of components that are genotoxic in human colon cells and high concentrations of components that induce oxidized DNA bases.

KEY WORDS

Probiotics
prebiotics
lactic acid bacteria
microflora
colon cancer
protective mechanisms
antigenotoxicity
fermentation
short-chain fatty acids
butyrate

Cited by (0)

1

From the Institute for Nutritional Physiology, Federal Research Centre for Nutrition, Karlsruhe, Germany, and the Department of Molecular Toxicology and Pharmacogenetics, Institute for Nutrition and Environment, Friedrich-Schiller-University Jena, Germany.

2

Presented at the symposium Probiotics and Prebiotics, held in Kiel, Germany, June 11–12, 1998.

3

Address reprint requests to BL Pool-Zobel, Department of Molecular Toxicology and Pharmacogenetics, Institute for Nutrition and Environment, Friedrich-Schiller-University, Jena Dornburgerstrasse 25, D-07743 Jena, Germany. E-mail: [email protected].