Dietary saturated fat promotes omega-3 polyunsaturated fatty acid incorporation into human plasma and erythrocytes

Research in animal models suggests that dietary saturated fat (SFA) enhances omega-3 polyunsaturated fatty acids (n-3PUFA) incorporation in membranes and tissue cells, when compared to dietary omega-6 polyunsaturated fat (n-6PUFA). N-6PUFA are known to compete with n-3PUFA for the same enzymes in their metabolic pathway. Therefore, we investigated blood lipid levels and n-3PUFA incorporation into plasma and erythrocytes following dietary supplementation with n-3PUFA [2.4g eicosapentaenoic acid (EPA): docosahexaenoic acid (DHA) daily], combined with either a high SFA diet or a high n-6PUFA diet. This was a randomized, dietary intervention trial, in parallel design involving 25 healthy adults aged 18 to 65 years. Blood samples were collected after an overnight fast at baseline and after 6 weeks of dietary intervention. A significantly higher increase in n-3PUFA into plasma and erythrocyte lipids was observed after the consumption of the SFA diet when compared with the n-6PUFA diet (P=0.017 and P=0.006, respectively). The SFA diet also caused an increase in total (P=0.021) and low density lipoprotein (LDL) cholesterol (P=0.011). Thus, n-3PUFA supplementation appears to be more effective in increasing tissue n-3PUFA levels when the background diet is rich in SFA rather than n-6PUFA, despite increase in total and LDL cholesterol levels.