[Linoleic conjugated acid: current interest in human nutrition]

Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of linoleic acid. The major dietary sources of CLA are meat from rumiants and dairy products. There are also foods enriched in CLA (by modification animal feed or addition of commercial CLA from cartamo oil). However, the major isomer of CLA in natural food is cis-9,trans-11 and commercial CLA contains approximately equal amounts of cis-9,trans-11 and trans-10,cis-12 isomers. Although CLA is minor component of the diet, at present CLA has provoked intense scientific research accompanied by an advertising boom. This is due to the potential health effects demonstrated in animal and cell culture experiments including effects on body composition, specially a reduction in body fat mass and anticarcinogenic, antidiabetogenic and immune modulating effects. The results obtained in human volunteers are limited and even sometimes contradictory. This review focuses on recently studies in humans. To draw conclusions on CLA's potential interest as a functional ingredient, additional studies are needed to clearly define optimal level of CLA intake, short and long term effects and side effects of each individual CLA isomer in order to determine its safety and efficacy.