Cholesterol dynamics in rats fed diets containing either canola oil or sunflower oil

The hypothesis, that canola oil, rich in monounsaturated and n-3 fatty acids lowers total body cholesterol unlike sunflower oil rich in n-6 fatty acids which appears to redistribute the exchangeable body cholesterol pools was tested. Male weanling Sprague-Dawley rats were fed nutritionally adequate diets containing either canola oil (CO diet) or sunflower oil (SFO diet). A third diet, (CONTROL diet), containing primarily beef tallow but sufficient amount of linoleic acid to prevent essential fatty acid deficiency was also employed. The effect of these diets on serum cholesterol, HDL-cholesterol, serum triglyceride and liver cholesterol was examined. To study the exchangeable body cholesterol pools, the rats were gauvaged with [4-14C]-cholesterol and radioactivity incorporated into serum, liver, heart, testes, spleen, faeces and kidney at various time intervals was determined. There was a significant reduction in the HDL-cholesterol concentration following the feeding of SFO diet whereas CO feeding had no effect. The cholesterol content in the hepatic tissue was increased by SFO diet while the CO had no significant effect as compared to the BT diet. Triacylglycerol concentration in the serum was lowered by both the SFO and CO diets to the same extent when compared to the BT diet. The level of triacylglycerol in the liver was not significantly altered by any of the diet treatments. Feeding sunflower oil containing diet to the rats resulted in higher incorporation of 14C-cholesterol in various pools examined in comparison to the group fed the canola oil. Excretion of 14C-cholesterol and its metabolites in the faeces was highest in the animals fed the canola oil containing diets. These data suggest that the liver accumulation of cholesterol following the feeding of a diet rich in sunflower oil containing high levels of n-6 fatty acids may be due to rapid absorption of cholesterol from the gut into the blood followed by rapid uptake by liver and other tissues as well as reduced excretion of cholesterol and its metabolites in the faeces.