Conversion of α-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women

TLDR

Women of reproductive age may convert α‑linolenic acid to long‑chain n‑3 fatty acids more efficiently than men, a capacity that could support fetal and neonatal DHA needs and explain observed sex differences in DHA status. The study aimed to quantify how much α‑linolenic acid women convert to eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids in vivo. This was done by giving 700 mg of [U‑13C]α‑linolenic acid and measuring the appearance of labeled fatty acids in plasma over 21 days. The labeled α‑linolenic acid accumulated mainly in cholesteryl esters, while EPA appeared equally in phosphatidylcholine and cholesteryl esters, and DPA and DHA were largely in phosphatidylcholine; net conversion rates were 21 % for EPA, 6 % for DPA, and 9 % for DHA, with 22 % exhaled as 13CO₂, indicating differential lipid‑class partitioning that could target specific tissues.

Abstract

The extent to which women of reproductive age are able to convert the n −3 fatty acid α-linolenic acid (ALNA) to eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) was investigated in vivo by measuring the concentrations of labelled fatty acids in plasma for 21 d following the ingestion of [ U − 13 C]ALNA (700 mg). [ 13 C]ALNA excursion was greatest in cholesteryl ester (CE) (224 (SEM 70) μmol/l over 21 d) compared with triacylglycerol (9-fold), non-esterified fatty acids (37-fold) and phosphatidylcholine (PC, 7-fold). EPA excursion was similar in both PC (42 (SEM 8) μmol/l) and CE (42 (SEM 9) μmol/l) over 21 d. In contrast both [ 13 C]DPA and [ 13 C]DHA were detected predominately in PC (18 (SEM 4) and 27 (SEM 7) μmol/l over 21 d, respectively). Estimated net fractional ALNA inter-conversion was EPA 21 %, DPA 6 % and DHA 9 %. Approximately 22 % of administered [ 13 C]ALNA was recovered as 13 CO 2 on breath over the first 24 h of the study. These results suggest differential partitioning of ALNA, EPA and DHA between plasma lipid classes, which may facilitate targeting of individual n −3 fatty acids to specific tissues. Comparison with previous studies suggests that women may possess a greater capacity for ALNA conversion than men. Such metabolic capacity may be important for meeting the demands of the fetus and neonate for DHA during pregnancy and lactation. Differences in DHA status between women both in the non-pregnant state and in pregnancy may reflect variations in metabolic capacity for DHA synthesis.