Beef tallow decreases colonic precancerous lesions and the concentration of fecal bile acids in rats

Epidemiological and animal studies suggest that beef protein and tallow may modulate the risk of colon cancer. One proposed mechanism is through changes in bile acid concentrations. High concentrations of bile acids are putative tumor promoters and are associated with a greater incidence of colon cancer. The present study examined the effect of beef protein and tallow on dimethylhydrazine (DMH)-induced preneoplastic lesions (aberrant crypt. AC and foci. ACF) in the colon and fecal bile acid concentrations in rats. Rats were administered DMH (15 mg/kg B.W.) once a week for two weeks by gavage. One week after the last carcinogen treatment, animals were fed either casein or beef protein as the protein source (20%) and soybean oil or tallow as the fat source (15%) in a 2 x 2 factorial design. Rats were fed for 9 weeks and a three day fecal collection performed in the final week. There was a significant effect of fat source on ACF, with beef tallow decreasing ACF relative to soybean oil (p=0.04). Fecal bile acid concentrations were significantly decreased in rats fed tallow compared to soybean oil. No significant effect of protein source or interaction between fat and protein sources were detected on number of ACF and bile acid concentrations. There was a significant positive correlation between the means of number of AC and total fecal bile acid concentration (r²=0.96. p=0.019). Therefore, beef tallow may decrease the risk of colon cancer by reducing bile acid concentrations.