, Volume 35, Issue 2, pp 131–135

Biosynthesis of conjugated linoleic acid in humans



This paper deals with the reanalysis of serum lipids from previous studies in which deuterated fatty acids were administered to a single person. Samples were reanalyzed to determine if the deuterated fatty acids were converted to deuterium-labeled conjugated linoleic acid (CLA, 9c, 11t-18∶2) or other CLA isomers. We found 11-trans-octadecenoate (fed as the triglyceride) was converted (Δ9 desaturase) to CLA, at a CLA enrichment ofca. 30%. The 11-cis-octadecenoate isomer was also converted to 9c, 11c-18∶2, but at <10% the concentration of the 11t-18∶1 isomer. No evidence (within our limits of detection) for conversion of 10-cis-or 10-trans-octadecenoate to the 10,12-CLA isomers (Δ12 desaturase) was found. No evidence for the conversion of 9-cis, 12-cis-octadecadienoate to CLA (via isomerase enzyme) was found. Although these data come from isomerase enzyme) was found. Although these data come from four single human subject studies, data from some 30 similar human studies have convinced us that the existence of a metabolic pathway in one subject may be extrapolated to the normal adult population.



conjugated linoleic acid


11-trans-octadecadienoic acid; 9c 11t-18∶2


ethyl ether


fatty acid(s)


fatty acid methyl ester(s)


gas chromatography


gas chromatography/mass spectrometry


petroleum ether






thin-layer chromatography


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Steinhart, C. (1996) Conjugated Linoleic Acid—The Good News About Animal Fat,J. Chem. Educ. 73, A302-A303.CrossRefGoogle Scholar
  2. 2.
    Ip, C., Briggs, S.P., Haegele, A.D., Thompson, H.J., Storkson, J., and Scimeca, J.A. (1996) The Efficacy of Conjugated Linoleic Acid in Mammary Cancer Prevention Is Independent of the Level or Type of Fat in the Diet,Carcinogenesis 17, 1045–1050.PubMedCrossRefGoogle Scholar
  3. 3.
    Belury, M.A. (1995) Conjugated Dienoic Linoleate: A Polyunsaturated Fatty Acid with Unique Chemoprotective Properties,Nutr. Rev. 53, 83–89.PubMedCrossRefGoogle Scholar
  4. 4.
    Christie, W.W. (1997) The Analysis of Conjugated Fatty Acids,Lipid Technol. (May), 73–75.Google Scholar
  5. 5.
    Kramer, J.K.G., Fellner, V., Dugan, M.E.R., Sauer, S.D., Mossoba, M.M., and Yurawecz, M.P. (1997) Evaluating Acid and Base Catalysts in the Methylation of Milk and Rumen Fatty Acids with Special Emphasis on Conjugated Dienes and Totaltrans Fatty Acids,Lipids 32, 1219–1228.PubMedCrossRefGoogle Scholar
  6. 6.
    Ha, Y.L., Storkson, J., and Pariza, M.W. (1990) Inhibition of Benzo(a)Pyrene-Induced Mouse Forestomach Neoplasia by Conjugated Dienoic Derivatives of Linoleic Acid,Cancer Res. 50, 1097–1101.PubMedGoogle Scholar
  7. 7.
    Sebedio, J.L., Juaneda, P., Dobson, G., Ramilison, J., Martin, J.C., Chardigny, J.M., and Christie, W.W. (1997) Metabolites of Conjugated Isomers of Linoleic Acid (CLA) in the Rat,Biochim. Biophys. Acta 1345, 5–10.PubMedGoogle Scholar
  8. 8.
    Fogerty, A.C., Ford, G.L., and Svoronos, D. (1988) Octadeca-9,11-dienoic Acid in Foodstuffs and in the Lipids of Human Blood and Breast Milk,Nutr. Rep. Int. 38, 937–944.Google Scholar
  9. 9.
    Pollard, M.R., Gunstone, F.D., James, A.T., and Morris, L.J. (1980) Desaturation of Positional and Geometric Isomers of Monoenoic Fatty Acids by Microsomal Preparations from Rat Liver,Lipids 15, 306–314.PubMedCrossRefGoogle Scholar
  10. 10.
    Salminen, M.M., Mutanen, M., Jauhiainen, M., and Aro, A. (1998) Dietarytrans Fatty Acids Increase Conjugated Linoleic Acid Levels in Human Serum,Nutr. Biochem. 9, 93–98.CrossRefGoogle Scholar
  11. 11.
    Aro, A., and Salminen, I. (1998) Difference Between Animal and Vegetabletrans Fatty Acids,Am. J. Clin. Nutr. 68, 918–919.PubMedGoogle Scholar
  12. 12.
    Chin, S.F., Liu, W., Storkson, J.M., Ha, Y.L., and Pariza, M.W. (1992) Dietary Sources of Conjugated Dienoic Isomers of Linoleic Acid, a Newly Recognized Class of Anticarcinagens,J. Food Comp. Anal. 5, 185–197.CrossRefGoogle Scholar
  13. 13.
    Griinari, J.M., and Bauman, D.E. (1999) Biosynthesis of Conjugated Linoleic Acid and Its Incorporation into Meat and Milk in Ruminants, inAdvances in Conjugated Linoleic Acid Research, Vol. 1 (Yurawecz, M.P., Mossoba, M.M., Kramer, J.K.G., Pariza, M.W., and Nelson, G.J., eds.), pp. 180–200, AOCS Press, Champaign.Google Scholar
  14. 14.
    Emken, E.A. (1979) Utilization and Effects of Isomeric Fatty Acids in Humans, inGeometrical and Positional Fatty Acid Isomers (Emken, E.A., and Dutton, H.J., eds.), pp. 99–129, American Oil Chemists' Society, Champaign.Google Scholar
  15. 15.
    Demmelmair, H., Sauerwald, T., Koletzko, B., and Richter, T. (1997) New Insights into Lipid and Fatty Acid Metabolismvia Stable Isotopes,Europ. J. Ped. 156 (suppl. 1), S70-S74.CrossRefGoogle Scholar
  16. 16.
    Descomps, B. (1995) Utilization of Stable Isotopes to Study Lipid Metabolism in Humans, inNew Trends in Lipid and Lipoprotein Analyses (Sebedio, J.L., and Perkins, E.G., eds.), pp. 299–316, AOCS Press, Champaign.Google Scholar
  17. 17.
    Emken, E.A., Rohwedder, W.K., Adlof, R.O., DeJarlais, W.J., and Gulley, R.M. (1986) Absorption and Distribution of Deuterium-Labeledtrans-andcis-11-Octadecenoic Acid in Human Plasma and Lipoprotein Lipids,Lipids 21, 589–595.PubMedCrossRefGoogle Scholar
  18. 18.
    Emken, E.A., Rohwedder, W.K., Adlof, R.O., DeJarlais, W.J., and Gulley, R.M. (1985)In vivo Distribution and Turnover oftrans- andcis-10-Octadecenoic Acid Isomers in Human Plasma Lipids,Biochim. Biophys. Acta 836:233–245.PubMedGoogle Scholar
  19. 19.
    Emken, E.A., Adlof, R.O., Rakoff, H., and Rohwedder, W.K. (1988) Metabolism of Deuterium-Labeled Linolenic, Linoleic, Oleic, Stearic and Palmitic Acid in Human Subjects, inSynthesis and Applications of Isotopically Labelled Compounds (Baillie, T.A., and Jones, J.R. eds.), pp. 713–716, Elsevier Science Publishers, Amsterdam.Google Scholar
  20. 20.
    Emken, E.A., Adlof, R.O., Rakoff, H., Rohwedder, W.K., and Gulley, R.M. (1990) Metabolismin vivo of Deuterium-Labelled Linolenic and Linoleic Acids in Humans,Biochem. Soc. Trans. 18:766–769.PubMedGoogle Scholar
  21. 21.
    Emken, E.A., Adlof, R.O., Rohwedder, W.K., and Gulley, R.M. (1992) Comparison of Linolenic and Linoleic Acid Metabolism in Man: Influence of Dietary Linoleic Acid, inEssential Fatty Acids and Eicosanoids (Sinclair, A., and Gibson, R., eds.) pp. 23–25, American Oil Chemists' Society, Champaign.Google Scholar
  22. 22.
    Christie, W.W. (1973)Lipid Analysis, pp. 85–102, Pergamon Press, New York.Google Scholar
  23. 23.
    Rohwedder, W.K. (1975) Mass Spectrometry of Lipids, inAnalysis of Lipids and Lipoproteins (Perkins, E.G., ed.), pp. 170–182. American Oil Chemists' Society, Champaign.Google Scholar
  24. 24.
    Rohwedder, W.K., Emken, E.A., and Wolf, D.J. (1985) Analysis of Deuterium Labeled Blood Lipids by Chemical Ionization Mass Spectrometry,Lipids 20, 303–310.PubMedCrossRefGoogle Scholar
  25. 25.
    Christie, W.W. (1994) Why I Dislike Boron Trifluoride/Methanol,Lipid Technol. (May/June), 66–68.Google Scholar
  26. 26.
    Zhang, A., and Chen, Z.Y. (1997) Oxidative Stability of Conjugated Linoleic Acids Relative to Other Polyunsaturated Fatty Acids,J. Am. Oil Chem. Soc. 74, 1611–1613.CrossRefGoogle Scholar
  27. 27.
    Ackman, R.G., (1997) Has Evolution and Long-term Coexistence Adapted Us to Cope withtrans Fatty Acids?J. Food Lipids 4:295–318.CrossRefGoogle Scholar
  28. 28.
    Jiang, J., Wolk, A., and Vessby, B. (1998) Relationship Between the Intake of Milk Fat and the Occurrence of Conjugated Linoleic Acid in Human Adipose Tissue, Ph. D. Thesis, Swedish University of Agricultural Sciences, Uppsala, Sweden, III: 1–18.Google Scholar
  29. 29.
    Emken, E.A., Adlof, R.O., and Gulley, R.M. (1994) Dietary Linoleic Acid Influences Desaturation and Acylation of Deuterium-Labeled Linoleic and Linolenic Acids in Young Adult Males,Biochim. Biophys. Acta 1213, 277–288.PubMedGoogle Scholar
  30. 30.
    Bauman, D.E., Corl, B.A., Baumgard, L.H., and Griinari, J.M., (1998)trans Fatty Acids, Conjugated Linoleic Acid and Milk Fat Synthesis,Proceedings of the Cornell Nutrition Conferencefor Feed Manufacturers, Rochester, NY, Oct. 20–22, pp. 95–103, Cornell University Press, Ithaca.Google Scholar

Copyright information

© AOCS Press 2000

Authors and Affiliations

  1. 1.Midwest Research ConsultantsPrinceville
  2. 2.Food Quality and Safety Research, NCAUR, USDA, ARSPeoria

Personalised recommendations