Incorporation of n-3 fatty acids into plasma and liver lipids of rats: importance of background dietary fat.

The health benefits of long-chain n-3 PUFA (20:5n-3 and 22:6n-3) depend on the extent of incorporation of these FA into plasma and tissue lipids. This study aimed to investigate the effect of the background dietary fat (saturated, monounsaturated, or n-6 polyunsaturated) on the quantitative incorporation of dietary 18:3n-3 and its elongated and desaturated products into the plasma and the liver lipids of rats. Female weanling Wistar rats (n = 54) were randomly assigned to six diet groups (n = 9). The fat added to the semipurified diets was tallow (SFA), tallow plus linseed oil (SFA-LNA), sunola oil (MUFA), sunola oil plus linseed oil (MUFA-LNA), sunflower oil (PUFA), or sunflower oil plus linseed oil (PUFA-LNA). At the completion of the 4-wk feeding period, quantitative FA analysis of the liver and plasma was undertaken by GC. The inclusion of linseed oil in the rat diets increased the level of 18:3n-3, 20:5n-3, and, to a smaller degree, 22:6n-3 in plasma and liver lipids regardless of the background dietary fat. The extent of incorporation of 18:3n-3, 20:5n-3, and 22:5n-3 followed the order SFA-LNA > MUFA-LNA > PUFA-LNA. Levels of 22:6n-3 were increased to a similar extent regardless of the type of major fat in the rat diets. This indicates that the background diet affects the incorporation in liver and plasma FA pools of the n-3 PUFA with the exception of 22:6n-3 and therefore the background diet has the potential to influence the already established health benefits of long-chain n-3 fatty acids.