Long-chain conversion of [13C]linoleic acid and alpha-linolenic acid in response to marked changes in their dietary intake in men

J Lipid Res. 2005 Feb;46(2):269-80. doi: 10.1194/jlr.M400225-JLR200. Epub 2004 Dec 1.


We studied the long-chain conversion of [U-13C]alpha-linolenic acid (ALA) and linoleic acid (LA) and responses of erythrocyte phospholipid composition to variation in the dietary ratios of 18:3n-3 (ALA) and 18:2n-6 (LA) for 12 weeks in 38 moderately hyperlipidemic men. Diets were enriched with either flaxseed oil (FXO; 17 g/day ALA, n=21) or sunflower oil (SO; 17 g/day LA, n=17). The FXO diet induced increases in phospholipid ALA (>3-fold), 20:5n-3 [eicosapentaenoic acid (EPA), >2-fold], and 22:5n-3 [docosapentaenoic acid (DPA), 50%] but no change in 22:6n-3 [docosahexanoic acid (DHA)], LA, or 20:4n-6 [arachidonic acid (AA)]. The increases in EPA and DPA but not DHA were similar to those in subjects given the SO diet enriched with 3 g of EPA plus DHA from fish oil (n=19). The SO diet induced a small increase in LA but no change in AA. Long-chain conversion of [U-13C]ALA and [U-13C]LA, calculated from peak plasma 13C concentrations after simple modeling for tracer dilution in subsets from the FXO (n=6) and SO (n=5) diets, was similar but low for the two tracers (i.e., AA, 0.2%; EPA, 0.3%; and DPA, 0.02%) and varied directly with precursor concentrations and inversely with concentrations of fatty acids of the alternative series. [13C]DHA formation was very low (<0.01%) with no dietary influences.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Arachidonic Acid / metabolism
  • Area Under Curve
  • Chromatography, Gas
  • Diet*
  • Docosahexaenoic Acids / metabolism
  • Eicosapentaenoic Acid / metabolism
  • Erythrocytes / metabolism*
  • Fatty Acids / metabolism
  • Fatty Acids, Unsaturated / metabolism
  • Humans
  • Linoleic Acid / chemistry*
  • Male
  • Middle Aged
  • Models, Biological
  • Phospholipids / blood*
  • Phospholipids / metabolism
  • Risk
  • Time Factors
  • alpha-Linolenic Acid / chemistry*


  • Fatty Acids
  • Fatty Acids, Unsaturated
  • Phospholipids
  • alpha-Linolenic Acid
  • Docosahexaenoic Acids
  • Arachidonic Acid
  • Linoleic Acid
  • Eicosapentaenoic Acid
  • docosapentaenoic acid