Failure of Conjugated Linoleic Acid Supplementation to Enhance Biosynthesis of Docosahexaenoic Acid From Alpha-Linolenic Acid in Healthy Human Volunteers

Prostaglandins Leukot Essent Fatty Acids. 2007 Mar;76(3):121-30. doi: 10.1016/j.plefa.2006.11.002. Epub 2007 Feb 1.


A rate-limiting step in docosahexaenoic acid (DHA) formation from alpha-linolenic acid (ALA) involves peroxisomal oxidation of 24:6n-3 to DHA. The aim of the study was to determine whether conjugated linoleic acid (CLA) would enhance conversion of ALA to DHA in humans on an ALA-supplemented diet. The subjects (n=8 per group) received daily supplementation of ALA (11g) and either CLA (3.2g) or placebo for 8 weeks. At baseline, 4 and 8 weeks, blood was collected for plasma fatty acid analysis and a number of physiological measures were examined. The ALA-supplemented diet increased plasma levels of ALA and eicosapentaenoic acid (EPA). The addition of CLA to the ALA diet resulted in increased plasma levels of CLA, as well as ALA and EPA. Plasma level of DHA was not increased with either the ALA alone or ALA plus CLA supplementation. The results demonstrated that CLA was not effective in enhancing DHA levels in plasma in healthy volunteers.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Analysis of Variance
  • Dietary Supplements*
  • Docosahexaenoic Acids / metabolism*
  • Eicosapentaenoic Acid / blood
  • Eicosapentaenoic Acid / metabolism
  • Fatty Acids, Unsaturated / blood
  • Humans
  • Linoleic Acids, Conjugated / administration & dosage
  • Linoleic Acids, Conjugated / metabolism
  • Linoleic Acids, Conjugated / pharmacology*
  • Lipids / blood
  • Middle Aged
  • Models, Biological
  • Time Factors
  • Treatment Failure
  • alpha-Linolenic Acid / administration & dosage
  • alpha-Linolenic Acid / metabolism
  • alpha-Linolenic Acid / pharmacology*


  • Fatty Acids, Unsaturated
  • Linoleic Acids, Conjugated
  • Lipids
  • alpha-Linolenic Acid
  • Docosahexaenoic Acids
  • Eicosapentaenoic Acid