We studied the effect of dietary
fatty acid composition on the
tumorigenesis of
colon cancer induced by methyl nitrosourea (MNU) in rats. Five groups of Sprague-Dawley male rats were fed with semi-synthetic diets that contained different proportions of
beef tallow,
soybean oil, alkana
oil, corn oil, and
fish oil for 180 days. Each group was matched with a control group fed with the same diet. The experimental groups were given MNU in PBS i.p. 6 times at weekly intervals. The control groups were given PBS only. The incidence of
colon cancer, the average volume of the
tumors,
PCNA, cell kinetics,
membrane lipid fluidity, ALP activity, and the content of
PGE2 in colonic mucous and the
fatty acid distribution in the testis pad fat were measured at the end of the experiment. The results showed that the incidence of
colon cancer and the average volume of the
tumors in animals fed with diets that contained mainly
beef tallow,
soybean oil, or alkana oil were significantly higher than that in animals fed with diets that contained mainly
fish oil. The diet containing 13.9% of SFA, 16.4% of MUFA, and 68.8% of PUFA showed the strongest inhibition effect. This may be due to the mechanism of protecting the
membrane lipid fluidity, decreasing the amount of
PCNA in colon cells, the number of
propidium iodine-labeled cells in S phase, the activity of ALP and inhibiting the production of AA and thus decreasing the amount of
PGE2.