The effect of dietary canola oil and sunflower oil on plasma lipids in healthy young men
Corner, Elizabeth J.
A 48-day metabolic study involving 8 normolipidemic men was divided into 4 diet periods: a 6 day pre-experimental, two-18 day experimental and a 6-day post experimental. Approximately 75% of the dietary fat (28% of total energy) was provided by a mixture of fats during the pre- and post-experimental periods and canola oil (CO) or sunflower oil (SO) during the experimental periods. The CO and SO diets were fed in a cross-over design. Saturated fatty acids provided 14, 5 and 7%, monounsaturated fatty acids 15, 20 and 7% and polyunsaturated fatty acids 7, 10 and 22% of total dietary energy in the mixed fat, CO and SO diets, respectively. The ratios of linoleic to linolenic acid were 2.6 to 1 and 73.9 to 1 in the CO and SO diets, respectively. Venous blood samples were taken at the beginning and end of each diet period from subjects who had fasted 12 hours. The CO and SO diets produced similar decreases in serum cholesterol (20 and 14%, respectively) and LDL-cholesterol (25 and 21%, respectively). Neither fat source affected plasma HDL-cholesterol or triglyceride levels. However, dietary fat source did have an effect on plasma phospholipid and cholesterol ester fatty acids: 18:1 n-9, 18:3 n-3 and 20:5 n-3 were significantly higher (p<0.05) and 18:2 n-6 significantly lower in the phosphatidyline (PC) fraction, 18:1 was significantly higher and 20:4 significantly lower in the phosphatidylethanolamine (PE) fraction, 18:1 and 20:5 were significantly higher and 20:4 and 22:6 were significantly lower in the lyso-PE fraction and 18:1, 18:3 and 20:5 were significantly higher and 18:2 significantly lower in cholesterol esters on the CO diet compared to the SO diet. This it would appear that the experimental diets had equal hypocholesterolemic effects and that consumption of the CO diet resulted in a higher n-3 fatty acid and lower n-6 fatty acid content in plasma phospholipids and cholesterol esters compared to the SO diet.