Safety of conjugated linoleic acid (CLA) in overweight or obese human volunteersThe main objective of the study was to investigate the safety of conjugated linoleic acid (CLA) in healthy volunteers. The effect of CLA on body composition was also investigated. The trial design was a randomized, double-blind placebo controlled study including 60 overweight or obese volunteers (body mass index (BMI) 27.5-39.0 kg/m 2 ). The subjects were divided into two groups receiving 3.4 g CLA or placebo (4.5 g olive oil) daily for 12 weeks. The safety was evaluated by analysis of blood parameters and by clinical examinations at baseline and week 12. Vital signs and adverse events were registered at baseline, week 6, and week 12. Bio Impedance Assessment was applied for body composition measurements. 55 subjects completed the study. Adverse events occurred in 10% of the subjects. No difference in adverse events or other safety parameters was found between the treatment groups. Small changes in the laboratory safety data were not regarded as clinically significant. Moreover, no clinically significant changes in vital signs were observed in any of the groups. In the CLA group, mean weight was reduced by 1.1 kg (paired t-test p = 0.005), while mean BMI was reduced by 0.4 kg/m 2 (p = 0.007). However, the overall treatment effect of CLA on body weight and BMI was not significant. There were no differences found between the groups with regard to efficacy parameters.The results indicate that CLA in the given dose is a safe substance in healthy populations with regard to the safety parameters investigated.

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CLA mixtures are now commercially available. They differ from each other with respect to their content of CLA isomers and their degree of purification. As a group of natural FA, CLA have been widely assumed to be safe. However, the suspected presence of both impurities and particular isomers might induce undesirable side effects. Despite this potential health risk, only a few CLA preparations have been tested under rigorous conditions for clinical efficacy and safety. Based on the limited results available, it is possible to suggest that preparations enriched in c9,t11 and t10,c12 isomers are preferable for human consumption compared to preparations containing four isomers, in terms both of safety and efficacy.