Effects of fish oil on fecal bacterial enzymes and steroid excretion in healthy volunteers: implications for colon cancer prevention.

Diet-induced changes in fecal excretion of secondary bile acids, certain neutral sterols, and bacterial enzyme activities are known to play a role in colon cancer development. Dietary fish oil (FO) has been implicated as a protective agent in colon carcinogenesis. In the present study, the effects of FO and corn oil (CO) on these fecal parameters were investigated in 24 healthy volunteers consuming a low- or a high-fat diet (30% or 50% of energy derived from fat). After four weeks of FO or CO supplementation (4.4 g of n-3 fatty acids/day), no significant differences were noted for fecal activities of beta-glucuronidase, beta-glucosidase, and sulfatase, nor was fecal bile acid excretion significantly affected by FO or CO consumption. However, daily excretion of the putative colon carcinogen 4-cholesten-3-one was significantly lower in the FO than in the CO period during low- and high-fat experiments. This may be another biochemical mechanism by which FO exerts its protective effect on colon cancer development.