Probiotics and colorectal cancer

The fecal flow conveys many carcinogens, and the intestinal flora plays a major role in colon health. Thus it has been suggested that some bacterial species could modulate in a positive way the mechanisms of intestinal carcinogenesis. The present article summarizes the main arguments in favor of a positive role of probiotics on the risk of colorectal tumors. Available arguments are mostly experimental, with the limits of extrapolating experimental data to human carcinogenesis. However, some studies in humans also suggest a potential beneficial effect, as for example an intervention study on adenoma recurrence. Most probably, according to the strain,probiotics exert different effects along the various steps of carcinogenesis. The most studied probiotics are lactic acid bacteriae with special interest for lactobacilli and bifidobacteriae. It has been suggested;that probiotics modulate the activities of the intestinal microflora via at least three diffent mechanisms: competition and shifting of other. constituents of the microflora; production of antibacterial agents thus controlling the growth of other constituents of the microflora; production of lactic acid and other organic acids, thus decreasing the intestinal pH and modulating the enzymatic, activity. On-going studies, especially European studies, should enable us to better determine the potential benefits of probiotics in colorectal cancer prevention in the next few years. (c) 2007 Elsevier Masson SAS.