Conjugated linoleic acid supplementation in humans - Metabolic effects

Supplementation with conjugated linoleic acid (CLA) induces a number of phy siological effects in experimental animals, including reduced body fat cont ent, decreased aortic lipid deposition, and improved serum lipid profile. C ontrolled trials on the effects of CLA in humans have hitherto been scarce. The aim of this study was to evaluate the effects of supplementation with CLA in healthy humans on anthropometric and metabolic variables and on the fatty acid composition of serum lipids and thrombocytes. Fifty-three health y men and women, aged 23-63 yr, were randomly assigned to supplementation w ith CLA (4.2 g/d) or the same amount of olive oil during 12 wk in a double- blind fashion. The proportion of body fat decreased (-3.8%, P < 0.001) in t he CLA-treated group, with a significant difference from the control group (P = 0.050). Body weight, body mass index, and sagittal abdominal diameter were unchanged. There were no major differences between the groups in serum lipoproteins, nonesterified fatty acids, plasma insulin, blood glucose, or plasminogen activator inhibitor 1 (PAI-1). In the CLA group the proportion s of stearic, docosatetraenoic, and docosapentaenoic acids increased in ser um lipids and thrombocytes, while proportions of palmitic, oleic, and di-ho mo-gamma -linolenic acids decreased, causing a decrease of the estimated De lta -6 and Delta -9 and an increase in the Delta -5 desaturase activities. These results suggest that supplementation with CLA may reduce the proporti on of body fat in humans and that CLA affects fatty acid metabolism. No eff ects on body weight, serum lipids, glucose metabolism, or PAI-1 were seen.