DHA Cycling Halves the DHA Supplementation Needed to Maintain Blood and Tissue Concentrations via Higher Synthesis from ALA in Long–Evans Rats

Abstract

ABSTRACT Background Eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) recommendations are frequently stated at 500 mg/d; however, adherence to these recommendations would result in a large global commercial EPA/DHA production deficit. Previously, our laboratory demonstrated that acute DHA intake in rats can increase the capacity for synthesis-secretion of n–3 (ω-3) polyunsaturated fatty acids (PUFAs). Objective We aimed to investigate the utility of a dietary DHA cycling strategy that employs 2 wk of repeated DHA feeding for a total of 3 cycles over 12 wk. Methods Male Long–Evans rats were fed a 10% fat diet by weight comprised of either 1) a 2-wk, 2% α-linolenic acid (ALA, DHA-ALA group 18:3n–3) diet followed by a 2-wk, 2% DHA + 2% ALA diet over 3 consecutive 4-wk periods (“DHA cycling,” DHA-ALA group); 2) a 2% DHA + 2% ALA diet (DHA group) for 12 wk; or 3) a 2% ALA-only diet (ALA group) for 12 wk. At 15 wk old, blood and tissue fatty acid concentrations and liver mRNA expression and 13C-DHA natural abundances were determined. Results DHA concentrations in plasma, erythrocytes, and whole blood between the DHA-ALA group and the DHA groups were not different (P ≥ 0.05), but were 72–110% higher (P < 0.05) than in the ALA group. Similarly, DHA concentrations in liver, heart, adipose, and brain were not different (P ≥ 0.05) between the DHA-fed groups, but were at least 62%, 72%, 320%, and 68% higher (P < 0.05) than in the ALA group in liver, heart, adipose, and skeletal muscle, respectively. Compound-specific isotope analysis indicated that 310% more liver DHA in the DHA-ALA group compared with the DHA group is derived from dietary ALA, and this was accompanied by a 123% and 93% higher expression of elongation of very long-chain (Elovl)2 and Elovl5, respectively, in the DHA-ALA group compared with the ALA group. Conclusions DHA cycling requires half the dietary DHA while achieving equal blood and tissue DHA concentrations in rats. Implementation of such dietary strategies in humans could reduce the gap between global dietary n–3 PUFA recommendations and commercial production.