Erythrocyte cell membrane phospholipid levels compared against reported dietary intakes of polyunsaturated fatty acids in pregnant Mexican women

Objective: To evaluate the validity of a food-frequency questionnaire (FFQ) for assessment of the dietary intakes of polyunsaturated fatty acid (PUFAs) against a biochemical marker of fat intake, erythrocyte cell membrane phospholipid levels, during pregnancy. Design: Cross-sectional analysis. Setting: Developmental Neurobiology Department, National Institute of Perinatology, Mexico City. Subjects: One hundred forty-six healthy pregnant women during the last trimester of pregnancy. Among women enrolled, the first 35 pregnant women (24%) had their erythrocytes analysed for fatty acid status. Methods: We administered an FFQ and compared intakes of PUFAS against their erythrocyte cell membrane concentrations, processed by gas chromatography. Results: Pearson correlation coefficients among alpha-linolenic acid (ALN), docosahexaenoic acid (DHA) and eicosapentaenoic acid in erythrocyte cell membranes against their crude dietary counterparts were 0.32, 0.35 and 0.36 (each P < 0.05). In a simple linear regression, erythrocyte DHA and arachidonic acid (AA) were significantly related to their respective dietary intakes (beta = 0.30, 95% confidence interval (CI): 0.007-0.60, P = 0.045 for DHA; beta = 0.49, 95% CI: 0.010-0.98, P = 0.044 for AA). Erythrocyte cell membrane ALN concentration (%/total) was only marginally related to ALN dietary intake (mg day(-1)) (beta = 0.52, 95% CI: -0.020-1.10, P = 0.061). However, after adjustment for long-chain n-3 PUFA/AA, this association reached significance (beta = 0.44, 95% CI: 0.026-0.825, P = 0.038). Main dietary sources for n-3 PUFAs were canned tuna fish and fresh catfish; for n-6 these were eggs. and cow's milk. The use of this FFQ in these pregnant Mexican women provided estimates of average long-term intakes of PUFAs and correlated reasonably well with their erythrocyte cell membrane phospholipid status. However, we need to consider that, during pregnancy, there is a faster turnover of PUFAs from fat storage that may modify the profile of erythrocyte PUFAs and lower the correlation between dietary intake and erythrocyte PUFAs.