Impact of novel methodologies on the analysis of conjugated linoleic acid (CLA). Implications of CLA feeding studies

Interest in conjugated linoleic acid (CLA) has increased in the past decade as a result of repot ts of several health benefits related to its consumpt ion. Naturally occurring CLA isomers are found in milk, dairy, and meat pro ducts from ruminants. Detailed isomeric composition of CLA in different che mical and biological matrices had been hindered by the lack of adequate ana lytical techniques. New methodologies were developed and used to determine the distribution of major and minor geometric and positional CLA isomers in cheese, beef, cow milk, human adipose, and human milk. Base-catalyzed meth ylation was used. A novel silver ion high-performance liquid chromatographi c procedure was developed, which successfully resolved up to 16 isomers. Th e double bond configuration and position for CLA isomers were confirmed by gas chromatography (GC)-direct deposirion-Fourier transform infrared spectr oscopy and CC-electron ionization mass spectrometry, respectively: The inco rporation of CLA isomers in tissues of animals fed CLA diets was also deter mined. Currently available analytical data suggest the need to re-evaluate prior CLA studies and their nutritional and biological implications.