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Synthesis of Conjugated Linoleic Acid in Ruminants and Humans

Biomedical studies have provided evidence that one or more isomers of conjugated linoleic acid (CLA) may have beneficial effects in the prevention of human chronic disease. Ruminant meat and milk are the principle source of CLA in the human diet. These foods contain numerous positional and geometric isomers of CLA with cis-9,trans-11 as the major isomer. The majority of CLA isomers in meat and milk originate from the isomerization of 18:2n-6 and 18:3n-3 in the rumen, reactions that proceed via different mechanisms catalysed by bacterial enzymes. Diet is the principal determinant of the amount and distribution of CLA isomers formed in the rumen. However, trans-7, cis-9 18:2 and cis-9, trans-11 18:2 are also formed in ruminant tissues and the mammary glands via the action of stearoyl CoA desaturase on trans-7 18:1 and trans-11 18:1, respectively. Virtually all trans-7, cis-9 18:2 and the majority of cis-9, trans-11 18:2 CLA in ruminant lipids and milk fat are synthesized endogenously. Diet is also the major factor determining the synthesis of CLA precursors in the rumen. Even though diet is the major source of CLA in humans, cis-9,trans-11 CLA is also synthesized endogenously with some evidence that CLA isomers may also be formed via the activity of microbial populations in the hindgut. The present chapter provides a comprehensive evaluation of the most recent evidence on the biochemical, microbial, nutritional and physiological factors influencing the biosynthesis of CLA isomers in ruminants and humans.

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30 Jul 2014
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From the book series:
Catalysis Series