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

  • Beth A. MacIntosh (a1), Christopher E. Ramsden (a2), Keturah R. Faurot (a3) (a4), Daisy Zamora (a4), Margaret Mangan (a5), Joseph R. Hibbeln (a6) and J. Douglas Mann (a7)...


Few trials have evaluated the metabolic effects and health outcomes of lowering dietary n-6 PUFA. The objectives of the present paper were (1) to report the methods employed to lower dietary n-6 PUFA, while either increasing or maintaining n-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 of n-3 PUFA or (2) a high-n-3 PUFA, low-n-6 PUFA (H3-L6) intervention designed to lower n-6 LA, while increasing the n-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 of n-3 PUFA did not change for the L6 group. Target increases in n-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 erythrocyte n-6 and n-3 fatty acid composition. Dietary LA can be lowered to ≤ 2·5 en%, with or without concurrent increases in dietary n-3 PUFA, in an outpatient clinical trial setting using this integrated diet method.

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Corresponding author

*Corresponding author: B. A. MacIntosh, fax +1 919 966 0576, email


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