Dietary substitution with an α-linolenic acid-rich vegetable oil increases eicosapentaenoic acid concentrations in tissues

Thirty healthy male volunteers were randomly allocated into two dietary treatment groups. The flaxseed group (n = 15) maintained a diet high in α- linolenic acid (α-LA; 18:3n-3) and low in linoleic acid (LA; 18:2n-6) by using a flaxseed oil and spread that are high in α-LA. The control group (n = 15) maintained a diet high in LA and low in α-LA, typifying a Western diet. Both groups maintained their diets for 4 wk, followed by another 4-wk period in which they supplemented the diets with fish oil [1.62 g eicosapentaenoic acid (EPA, 20:5n-3) daily and 1.08 g docosahexaenoic acid (DHA, 22:6n-3) daily] in a triglyceride form. The flaxseed oil-containing diet resulted in significant increases in ←a-LA concentrations in the plasma phospholipid, cholesteryl ester, and triglyceride fractions (eightfold increase) and neutrophil phospholipids (50% increase). EPA concentrations increased by 2.5-fold in the plasma lipid fractions and neutrophil phospholipids. After fish-oil supplementation EPA concentrations increased in parallel in both dietary groups, remaining higher in the flaxseed group for both the plasma lipid fractions and neutrophil phospholipids. The results indicate that α-LA-rich vegetable oils can be used in a domestic setting (in conjunction with a background diet low in LA) to elevate EPA in tissues to concentrations comparable with those associated with fish-oil supplementation.