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ARS Home » Research » Publications at this Location » Publication #106440
Title: THE BIOSYNTHESIS OF CONJUGATED LINOLEIC ACID IN HUMANS

Author
item Adlof, Richard
item Duval, Sandra
item EMKEN, EDWARD - MIDWEST RES CONSULTANT

Submitted to: Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Conjugated linoleic acid (CLA) is a fat found in milk, dairy products, and the meats of ruminant animals and has been associated with the reduction of chemically induced cancers in mice and rats and the suppression of atherosclerosis in rats. The CLA available commercially as a diet supplement is composed of a mixture of fats closely related in structure. The biosynthesis of CLA from other fats in living things has been documented in animals but not in humans. A specific "trans" fat is converted to CLA in the pig. Does this occur in humans? Our group fed many of these fats to humans. Samples were reanalyzed for CLA or CLA products. The "trans" fat pathway was found; the first time such a biosynthesis has been documented in humans.

Technical Abstract: Conjugated linoleic acid (CLA; 9c,11t-18:2), a commercially available diet supplement, has been implicated in a variety of beneficial physiological and biochemical effects in humans. It has been demonstrated in rats that 11t-18:1 is converted (via 9 desaturase) to CLA and that both the 9,11- and 10,12-18:2 CLA isomers are produced in conventional but not germ-free rats fed linoleic acid (9c,12c-18:2), the latter conversion due perhaps to an isomerase enzyme. Samples from human metabolism studies in which deuterium-labelled fats were fed were reanalyzed to determine if detectable amounts of deuterium-labelled CLA and CLA metabolites were formed. We found 11-trans-octadecenoate (fed as the triglyceride) was converted (9 desaturase) to CLA, at a CLA enrichment of ca. 30%. The 11-cis-octadecenoate isomer was also converted to CLA but at <10% the concentration of the 11t-18:1. No evidence for conversion of 10-cis- or 10-trans-octadecenoate to the 10,12-CLA isomer (12 desaturase) was found. No evidence for the conversion of 9-cis,12-cis-octadecadienoate CLA (via isomerase enzyme) was found.