The Journal of Nutrition Vol. 127 No. 3 March 1997, pp. 449-457
Copyright ©1997 by the American Society for Nutritional Sciences

Diet and Carcinogen Alter the Fecal Microbial Populations of Rats

Manuscript received 16 September 1996. Initial reviews completed 15 October 1996. Revision accepted 14 November 1996.

Kenneth G. Maciorowski^*, Nancy D. Turner, Joanne R. Lupton^{, **}, Robert S. Chapkin^{, **}, Casendra L. Shermer^*, Sang D. Ha^*, , and Steven C. Ricke^{*, **,}

^* Department of Poultry Science,  Department of Animal Science and ^** Graduate Faculty of Nutrition, Texas A&M University, College Station, TX 77843-2472

An analysis of viable bacterial populations enumerated on carbohydrate selective media was used to simulate the colonic environment in vitro and determine if differential media could detect significant microbial shifts due to dietary fiber source, dietary fat source, and carcinogen. Male Sprague-Dawley rats were provided with either pectin or cellulose as a fiber source, either corn or fish oil as a source of fatty acids, and injected with either azoxymethane (AOM), a gastrointestinal carcinogen, or saline in a 2 × 2 × 2 factorial design. At 6 and 10 mo of age, fresh feces were collected, homogenized in anaerobic buffer and anaerobically plated onto differential media. Diets containing pectin supported more anaerobes at 6 mo of age (P < 0.01) than diets containing cellulose. Rats injected with AOM and consuming either pectin or corn oil supported more anaerobes at 10 mo of age (P < 0.05) than rats injected with saline and consuming the same diets. Rats consuming cellulose and receiving AOM but not expressing tumors possessed larger anaerobic populations at 10 mo of age (P < 0.05) than rats consuming cellulose, injected with AOM and expressing tumors. These effects show that gastrointestinal bacterial populations, as measured by carbohydrate specific media, respond to dietary changes such as dietary fiber source, and thus may play a key role in the etiology of colon cancer.

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