[Effect of conjugated linoleic acid (CLA) on human lipid profile]

The term conjugated linoleic acid (CLA) concerns a group of isomers of linoleic acid, which are characterized by having conjugated double bonds in several positions and conformations. CLA is found naturally in some foods, but since CLA was first held to cause beneficial effects on various health-related issues, many investigations have been conducted to elucidate the effects of dietary supplementation with CLA. The effects of CLA on lipid profiles on animals have been extensively studied, and there is sound evidence of its benefits in blood metabolic markers. However, clinical trials in humans have provided ambiguous results. The aim of this review was to gather up-to-date available data about the effects of CLA on human lipid profile. Although most studies did not show any significant effect in none of the studied variables, some trials reported both beneficial and detrimental effects on total cholesterol, LDL-c, HDL-c, atherogenic index, triglycerides and lipoprotein(a). This discrepancy could be due to differences in dosage, isomer composition, duration of the study, placebo and participating subjects, among others. However, studies with a duration of two weeks, carried out using a mix of equal amounts of the two main CLA isomers (9-cis, 11-trans and 10-trans, 12-cis) and with doses of 3 to 4 grams per day, seem to offer the most beneficial results.