Reassessment of the antioxidant activity of conjugated linoleic acids

Abstract

The anticarcinogenic effect of conjugated linoleic acids (CLA) has been attributed to their antioxidant activity. Strong evidence is lacking, however, to substantiate that CLA is an antioxidant. The objective of this study was, therefore, to test whether CLA is an antioxidant or a prooxidant in canola oil. The oxidation was conducted at 90°C by monitoring oxygen uptake and changes in linoleic acid and α‐linolenic acid. Free CLA and CLA methyl ester (CLAME) accelerated lipid oxidation in canola oil. The prooxidant activity of CLA and CLAME was dose‐dependent at concentrations ranging from 0.1 to 1.0% in canola oil heated at 90°C. CLA‐containing triacylglycerol, however, was neither an antioxidant nor a prooxidant. Under the present experimental conditions, CLA was not an antioxidant in fats and oil.