Conjugated Linoleic Acid Intake In Humans: A Systematic Review Focusing on Its Effect on Body Composition, Glucose, and Lipid Metabolism

Studies performed on different species show that the consumption of conjugated linoleic acid (CLA) leads to a loss of fat and total body weight, reduces the plasma concentrations of total and LDL cholesterol, and has an antiinflammatory effect. This article reviews the clinical trials on human beings that evaluate how mixtures of CLA isomers administered as supplements or CLA-enriched products can affect total body weight, body composition, plasma lipid profile, glycemia, insulinemia, insulin sensitivity, lipid oxidation, and inflammation. After analyzing the few studies published to date in reduced samples of healthy humans or patients with overweight, obesity, metabolic syndrome, or diabetes, we deduce that there is not enough evidence to show that conjugated linoleic acid has an effect on weight and body composition in humans. However, some of these studies have observed that the administration of various CLA isomers has adverse effects on lipid profile (it decreases HDL cholesterol concentration and increases Lp(a) circulating levels), glucose metabolism (glycemia, insulinemia or insulin sensitivity), lipid oxidation, inflammation, or endothelial function. Therefore, long-term randomized clinical trials, controlled with placebo, need to be made in large samples of patients to evaluate the efficacy and safety of CLA isomers before its indiscriminate use in human beings can be recommended.

Keywords:

• conjugated linoleic acid
• body composition
• weight
• glucose metabolism
• lipid metabolism

ACKNOWLEDGMENTS

This study was partly funded by two grants from the Instituto de Salud Carlos III, Red de Centros RCMN (C03/08), and Red de Grupos (G03/140), Madrid, Spain.

Notes

∗All the trials determined body weight. Gaullier et al. (2004) were the only ones to observe a significant decrease in weight attributable to the consumption of CLA. VLCD = Very low calorie diet.^# Type 2 diabetic patients.

^# The original article by Gaullier et al. published in 2005 is an extension of the original study published by the same author in 2004 (Gaullier et al. 2004).

#Visceral or subcutaneous adipose area