Low-n-6 and low-n-6 plus high-n-3 diets for use in clinical research

Abstract

Few trials have evaluated the metabolic effects and health outcomes of lowering dietaryn-6 PUFA. The objectives of the present paper were (1) to report the methods employed to lower dietaryn-6 PUFA, while either increasing or maintainingn-3 PUFA intake and (2) to validate our methods with 24 h recalls and erythrocyte fatty acid analyses. A total of sixty-seven subjects were randomised to either (1) an average-n-3 PUFA, low-n-6 PUFA (L6) intervention designed to lower linoleic acid (LA; ≤ 2·5 % of energy (en%)) and arachidonic acid ( ≤ 60 mg/d), while maintaining an average US intake ofn-3 PUFA or (2) a high-n-3 PUFA, low-n-6 PUFA (H3-L6) intervention designed to lowern-6 LA, while increasing then-3 PUFA α-linolenic acid (ALA; ≥ 1·5 en%) and EPA+DHA ( ≥ 1000 mg/d). Pre- and intra-intervention nutrient intakes were estimated with six 24 h dietary recalls per subject. Both groups achieved the targeted reductions in dietary LA to ≤ 2·5 en% (median LA 2·45 (2·1, 3·1);P< 0·001). Intakes ofn-3 PUFA did not change for the L6 group. Target increases inn-3 ALA (median 1·6 en%, (1·3, 2·0),P< 0·001) and EPA+DHA (1482 mg, (374, 2558),P< 0·001) were achieved in the H3-L6 group. Dietary changes were validated by corresponding changes in erythrocyten-6 andn-3 fatty acid composition. Dietary LA can be lowered to ≤ 2·5 en%, with or without concurrent increases in dietaryn-3 PUFA, in an outpatient clinical trial setting using this integrated diet method.