STIMULATORY EFFECTS OF HIGH-FAT DIETS ON COLON CELL-PROLIFERATION DEPEND ON THE TYPE OF DIETARY-FAT AND SITE OF THE COLON

To compare the effects of various types of dietary fat on colon cell p roliferation used as an intermediate biomarker for colon carcinogenesi s, groups of 10 male Sprague-Dawley rats were fed one of four high-fat diets (45% of total calories from corn oil, butter beef tallow, and f ish oil) for three weeks. As a control, a low-fat diet (15% of total c alories from corn oil) was fed to a separate group. Cell proliferation was measured by in vivo incorporation of bromodeoxyuridine into DNA i n the proximal and distal colon. Total lipids in feces were measured b y a gravimetric method There were significant differences in colon cel l proliferation among the diet groups, where the high corn oil diet st imulated cell proliferation in proximal and distal colon compared with the high fish oil diet (p < 0.05). The protective effect of the high fish oil diet on cell proliferation was similar to that of the low cor n oil diet. The effects of high beef tallow and butter diets on colon cell proliferation were highly dependent on sites of the colon, becaus e the hyperproliferative effects by these diets were found only in the distal colon (p < 0.05). Fecal total lipids and fecal lipid concentra tions were significantly affected by the dietary fat sources, in that the groups fed the saturated fats, such as butter and beef tallow, exc reted more lipids into feces than did the groups fed the unsaturated f ats, such as corn oil and fish oil. Fecal lipids were significantly co rrelated to colon cell proliferation in the way that distal colon cell proliferation increases as fecal lipids increase. Therefore, these da ta suggest that high levels of dietary fats may not always promote col on carcinogenesis, and the effects may be dependent on the types of di etary fat and sites of the colon.