ABSTRACT
Epidemiological evidence clearly links dietary fat intake with colorectal cancer risk. There are two major families of dietary polyunsaturated fatty acids: the n-3 and n-6 families. Western style diets characterized by high intakes of energy, fat, meat, refined grains, and sugar combined with low intakes of fiber, calcium, and fruits and vegetables have been strongly linked to an increased risk of colorectal cancer. Studies in humans and in animal models overwhelmingly indicate a protective effect of n-3 fatty acids and the mechanism is largely thought to be related to a reduction in eicosanoid biosynthesis. The ability of dietary fatty acids to inhibit intestinal tumorigenesis has been explained by their effects on prostaglandin biosynthesis. Dietary fish oils reduce cyclooxygenase (COX)-2 expression in an azoxymethane-induced rat colonic tumor model and immunoreactive COX-1 and -2 protein levels in dimethylbenz(α)anthracene-induced mammary tumors, whereas oils rich in n-6 fatty acids increase COX-2 expression.
