Linoleic acid is associated with lower long-chain n-6 and n-3 fatty acids in red blood cell lipids of Canadian pregnant women

Background: Arachidonic (ARA), eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids are important in membrane glycerophospholipids. Higher maternal blood ARA, EPA, and DHA concentrations in gestation are associated with higher maternal-to-fetal transfer of ARA, EPA, and DHA, respectively, which emphasizes the importance of maternal fatty acid status in gestation. As in the brain, red blood cell (RBC) ethanolamine phosphoglycerides (EPGs) are high in plasmalogen, ARA, and DHA. Objective: We determined the relation between dietary n-6 (omega 6) and n-3 (omega-3) fatty acid intakes and n-6 and n-3 fatty acids in RBC EPGs and phosphatidylcholine in near-term pregnant women. Design: The subjects were 105 healthy Canadian pregnant (36 wk gestation) women. Fatty acid intakes were estimated by food-frequency questionnaire, and fasting venous blood samples were collected. Results: DHA and EPA intakes were positively associated with RBC EPG and phosphatidylcholine concentrations of DHA (rho = 0.309 and 0.369, respectively; P < 0.001) and EPA (rho = 0.391 and 0.228, respectively; P < 0.001) and inversely associated with RBC EPG 22: 4n-6 and 22: 5-6 (P < 0.001). In RBCs, concentrations of linoleic acid (LA, 18: 2n-6) were inversely associated with DHA, EPA, and ARA, respectively, in EPGs (r = -0.432, P < 0.01; r = -0.201, P < 0.04; and r = -0.303, P < 0.01) and phosphatidylcholine (r = -0.460, -0.490, and -0.604; P < 0.01 for all). Conclusions: Membrane fatty acids are influenced by the amount and balance of fatty acid substrates. Our results suggest the competitive interaction of LA with ARA, EPA, and DHA, with no evidence that higher LA increases ARA. Biochemical indicators to suggest that DHA is limiting are present in our population. This trial was registered at clinicaltrials. gov as NCT00620672. Am J Clin Nutr 2010; 91: 23-31.