Paper Del Cancer De Colon

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Journal of Nutritional Biochemistry 20 (2009) 743 – 752

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Gastrointestinal microflora, food components and colon cancer prevention
Cindy D. Davis⁎, John A. Milner
Nutritional Science Research Group, National Cancer Institute, Rockville, MD 20892, USA Received 8 January 2009; received in revised form 27 May 2009; accepted 4June 2009

Abstract Evidence that the intestinal microbiota is intrinsically linked with overall health, including cancer risk, is emerging. Moreover, its composition is not fixed but can be influenced by several dietary components. Dietary modifiers, including the consumption of live bacteria (probiotics) and indigestible or limited digestible food constituents such as oligosaccharides(prebiotics) and polyphenols or both (synbiotics), are recognized modifiers of the numbers and types of microbes and have been reported to reduce colon cancer risk experimentally. Microorganisms also have the ability to generate bioactive compounds from food components. Examples include equol from isoflavones, enterodiol and enterolactone from lignans and urolithins from ellagic acid, which have alsobeen demonstrated to retard experimentally induced cancers. The gastrointestinal microbiota can also influence both sides of the energy balance equation, namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Because of the link between obesity and cancer incidence and mortality, this complex complexiondeserves greater attention. Overall, a dynamic interrelationship exists between the intestinal microbiota and colon cancer risk, which can be modified by dietary components and eating behaviors. Published by Elsevier Inc.
Keywords: Prebiotics; Probiotics; Microbiota; Colon cancer

1. Microbes and colon cancer The adult human gut is estimated to contain 100 trillion microbial organisms,collectively referred to as the microbiota [1,2]. The human microbiota is known to be dominated by strict anaerobes including Bacteriodes, Eubacterium, Bifidobacterium, Fusobacterium, Peptostreptococcus and Atopobium [3]. Facultative anaerobes occur in numbers approximately 1000-fold lower and include lactobacilli, enterococci, streptococci and Enterobacteriaceae [4]. More than 500 different bacterialspecies may be present in the normal commensal microbiota, although the exact number and the variability among individuals remain an area of investigation [5]. Advances in defining the quality, quantity and physiologic activity of the intestinal microbiota have occurred as a result of the conversion from culture-based techniques to metagenomics, an emerging field in which the

⁎ Correspondingauthor. Nutritional Science Research Group, Division of Cancer Prevention, National Cancer Institute, Rockville, MD 208927328, USA. Tel: +1 301 594 9692; fax: +1 301 480 3925. E-mail address: davisci@mail.nih.gov (C.D. Davis). 0955-2863/$ – see front matter. Published by Elsevier Inc. doi:10.1016/j.jnutbio.2009.06.001

power of genomic analysis (the analysis of the entire DNA in an organism) isapplied to entire communities of microbes. A benefit of this approach is the elimination of isolating and culturing individual microbial species. One limitation is that stool and mucosal community populations differ [6,7]. Thus, the analysis of the bacteria in the stool probably does not always reflect that in early parts of the gastrointestinal tract. A complex dynamic relationship between the hostand the gastrointestinal bacteria occurs shortly after birth [8]. The microbiota diversifies as a function of age to form an intestinal microbiota that is unique for each individual [8]. Several findings suggest that the microbial cohort remains relatively constant once adulthood is reached; however, the composition of the resident biota may alter as a result of environmental factors such as diet...