Dietary and erythrocyte fatty acids in experimental colorectal carcinogenesis

The influence of dietary fat on the erythrocyte stearic:oleic acid ratio was investigated in an experimental model of colorectal cancer. One hundred male Wistar rats were divided into four separate dietary groups: A (5% saturated fat), B (20% saturated fat), C (5% n-6 unsaturated fat) or D (20% n-6 unsaturated fat). Colorectal tumours were induced by intraperitoneal injection of azoxymethane (n = 60) and control animals received saline (n = 40). Animals were killed after 26 weeks and erythrocyte fatty acid profiles were determined by gas liquid chromatography. Although there were no differences in the incidence of adenoma formation in the four dietary groups, there was a significantly lower incidence of carcinomas in rats fed a 5% or 20% unsaturated fat diet when compared with either a 5% (P less than 0.05) or a 20% saturated fat diet (P less than 0.01). Multivariate analysis of fatty acid profiles demonstrated that both the type and quantity of dietary fat had a highly significant influence on the fatty acid profile of erythrocytes. The stearic:oleic acid ratio varied considerably between the four dietary groups but was only significantly lower in tumour bearing animals compared with controls in group B (20% saturated fat diet).