Journal Name:
Reprod. Nutr. Dev.
Article Title:
Conversion of α-linolenic acid to longer-chain polyunsaturated fatty acids in human adults
Date Written:
2005
Volume:
45
Number:
0
Page:
581
Author(s):
Burdge, G.C.; Calder, P.
Article:
The principal biological role of α-linolenic acid (ALA; 18:3n-3) appears to be as a precursor for the synthesis of longer chain n-3 polyunsaturated fatty acids (PUFA). Increasing ALA intake for a period of weeks to months results in an increase in the proportion of eicosapentaenoic acid (EPA; 20:5n-3) in plasma lipids, in erythrocytes, leukocytes, platelets and in breast milk but there is no increase in docosahexaenoic acid (DHA; 22:6n-3), which may even decline in some pools at high ALA intakes. Stable isotope tracer studies indicate that conversion of ALA to EPA occurs but is limited in men and that further transformation to DHA is very low. There are important differences between men and women in capacity for synthesis of EPA and DHA from ALA and this may be affected by physiological state (e.g., pregnancy). The fractional conversion of ALA to the longer chain n-3 PUFA is greater in women which may be due to a regulatory effect of estrogen. A lower proportion of ALA is used for β-oxidation in women compared with men. Further, if demands for EPA and DHA are modest and primarily serve to support membrane turnover and renewal in adults, then it is possible that in healthy individuals consuming a balanced diet limited capacity for synthesis of EPA and DHA may be sufficient to maintain tissue function. However, in situations where demand for long chain n-3 PUFA, especially DHA, is increased (e.g., during pregnancy and lactation), then synthesis from ALA may be insufficient to meet the demand, although there may be physiological mechanisms by which ALA conversion is up-regulated.
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