Probiotics and the Prevention of Colon Cancer

The evidence that our intestinal bacteria or microflora is important to our overall health continues to mount. I would like to present some information about the benefits of probiotics and prebiotics in preventing colon cancer.

Before going further, I would like define a couple of terms.

You are already familiar with probiotics, but the term prebiotics may be less well known. Prebiotics are non-digestible starches found in certain fruits, vegetables and cereals. They are beneficial because they stimulate the growth of bifidobacteria and lactobacillus, both good bacteria. These two bacteria are able to digest or ferment prebiotic starches to produce short chain fatty acids (SCFAs). In experimental studies, the SCFAs enhance the function of the colon lining cells and have been helpful in the prevention of colon cancer.

When a probiotic is combined with a prebiotic, for example in a capsule, it is known as a synbiotic.

During the last 10 years, there has been a considerable amount of interest in how intestinal bacteria and diet can possibly alter the risk of colon cancer (2). Evidence from a wide range of sources supports the view that an individual's colonic microflora and diet are both involved in the development of colon cancer. Western diets high in animal products including fat, cholesterol and protein have demonstrated carcinogenic properties in experimental animal studies (3). In the 1970s, it was noted that colon cancer risk increased among descendents of persons in low-risk populations after moving to developed countries and converting to a Western diet (3).

The composition of an individual's diet influences the predominant type of intestinal bacteria. The breakdown products of meat and fat that enter the colon can stimulate harmful intestinal bacteria to produce chemicals that pose a risk to the development of cancer (3).

A study published in 1997 indicated how important the intestinal bacteria and diet are in the development of colon cancer. When germ-free animals were exposed to known colon carcinogens, only 20% developed chemically induced colon cancer. But when the same animals with normal intestinal bacteria were exposed to the carcinogen, 93% developed colon tumors (5).

The mechanisms by which probiotics may inhibit colon cancer are beginning to be understood. In an experimental animal study:

Bifidobacteria inhibited the harmful bacteria from making enzymes that produced carcinogens derived from bile acids and residue of ingested meat (4).

Probiotics altered the pH or acid level in the colon, which reduces the growth potential of harmful bacteria.

Probiotics stimulated the intestinal immune system to destroy abnormal colon cells with altered DNA or chromosomes (4).

Prebiotic studies have discovered that by increasing the amount of prebiotics called fructooligosaccharides (FOS) in the diet increased intestinal levels of bifidobacteria. In turn, this produced more of the SCFA, called butyrate. Experimental studies have found that butyrate reduces chemically induced colon cancer in animal studies.

Published research indicates the following about butyrate:

Has anti-carcinogenic properties, inhibiting the growth and proliferation of tumor cell lines

Induces differentiation of tumor cells, producing a cell type similar to that of the normal mature cell

Induces apoptosis or programmed cell death of human colorectal cancer cells (5)

The combination of a pro- and a prebiotic has a synergistic effect, greater than that of either the pro- or prebiotic administered individually. Several studies of synbiotics have shown that the combination of a bifidobacteria strain and the prebiotic FOS was more successful at decreasing carcinogen induced cell damage (2,7).

The advances in the research into how intestinal bacteria and diet influence the risk for colon cancer are amazing. At this point there are no human clinical studies that have shown that probiotics and prebiotics prevent colon cancer, but the studies should encourage us all to eat a healthy diet containing fresh fruits, vegetables and high-fiber cereals. This diet enhances the healthy intestinal bacteria and lessens the production of potential colon carcinogens.

Synbiotics like EndoMune may be beneficial in lessening the production of intestinal carcinogens. Stay tuned for further research news.

1) Cancer Screening in the Primary Care Setting.William F. Miser, MD, MA. Primary Care: Clinics in Office Practice - Volume 34, Issue 1 (March 2007)
2) Role of probiotics, prebiotics and synbiotics in chemoprevention for colorectal cancer.
Fotiadis CI, Stoidis CN, Spyropoulos BG, Zografos ED.World J Gastroenterol. 2008 Nov 14;14(42):6453-7.
3)Diet, anaerobic bacterial metabolism, and colon cancer: a review of the literature.
McGarr SE, Ridlon JM, Hylemon PB.J Clin Gastroenterol. 2005 Feb;39(2):98-109. Review
4) Role of Probiotics and Prebiotics in Colon Cancer Prevention: Postulated Mechanisms and In-vivo Evidence. Liong M. Int J Mol Sci. 2008, 9, 854-863
5)Possible mechanisms by which pro- and prebiotics influence colon carcinogenesis and tumor growth.Reddy BS.J Nutr. 1999 Jul;129(7 Suppl):1478S-82S. Review.
6) Butyrate is only one of several growth inhibitors produced during gut flora-mediated fermentation of dietary fibre sources.Beyer-Sehlmeyer G, Glei M, Hartmann E, Hughes R, Persin C, Böhm V, Rowland I, Schubert R, Jahreis G, Pool-Zobel BL.Br J Nutr. 2003 Dec;90(6):1057-
7) A synbiotic combination of resistant starch and Bifidobacterium lactis facilitates apoptotic deletion of carcinogen-damaged cells in rat colon.Le Leu RK, Brown IL, Hu Y, Bird AR, Jackson M, Esterman A, Young GP.J Nutr. 2005 May;135(5):996-1001.