Volume 88, Issue 4, October (2002), pp. 411-421 © The Author 2002
doi:10.1079/BJN2002689

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

Graham C. Burdge and Stephen A. Wootton
Institute of Human Nutrition, University of Southampton, Southampton, UK

 (Received 5 October 2001–Revised 30 May 2002–Accepted 19 June 2002)

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-¹³C]ALNA (700 mg). [¹³C]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 [¹³C]DPA and [¹³C]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 [¹³C]ALNA was recovered as ¹³CO₂ 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.

Abbreviations: ALNA; α-linolenic acid; AUC; area under the curve; CE; cholesteryl ester; DHA; docosahexaenoic acid; DPA; docosapentaenoic acid; EPA; eicosapentaenoic acid; FAME; fatty acid methyl esters; GC–C-IRMS; gas chromatography–combustion-isotope ratio mass spectrometry; LCPUFA; long-chain polyunsaturated fatty acid; NEFA; non-esterified fatty acid; PC; phosphatidylcholine; TAG; triacylglycerol

Keywords:
Women: alpha-Linolenic acid: Stable isotopes: Docosahexaenoic acid: Plasma