Metabolism of c9,t11-conjugated linoleic acid (CLA) in humans

The c9,t11 isomer of conjugated linoleic acid (CLA) is the most abundant CLA form present in the human diet, and is particularly prevalent in milk and dairy products, and is known to exert several health benefits in experimental animal models. A possible mechanism of action of c9,t11CLA relies on its metabolism via desaturases and elongases and partial beta oxidation in peroxisomes. In this study, we aimed to establish plasma incorporation of c9,t11CLA and its downstream metabolites in healthy volunteers after daily dietary intakes of 0.8 g, 1.6 g or 3.2 g of c9,t11CLA in capsule form for two months. Following supplementation, the plasma concentrations of c9,t11CLA and its metabolites conjugated dienes (CD) 18:3 and the beta oxidation product CD 16:2 were incorporated in a linear fashion, while on the other hand CD 20:3 reached a plateau following intakes of 1.6 g/d of dietary intake, and was not further increased following higher CLA intakes. We may conclude that supplementation of c9,t11 CLA levels result in linear responses of CLA and its main metabolites in plasma. In addition, only the highest concentration of CLA intake tested (3.2 g/d) yielded plasma concentrations of CLA and metabolites close to the range found sufficient to exert nutritional effects in experimental animal models.