Conjugated linoleic acids: formation and metabolic effects

Conjugated linoleic acids (CLAs) have been the subject of an increasing num ber of studies in the past few years. This substance group exhibits a numbe r of biological and physiological effects. It has been shown that CLAs enha nce the immune function by counteracting catabolic effects of immune stimul ation. Numerous studies confirmed the anticarcinogenic activity of CLAs in animals and in vitro models so far, however no research into anticarcinogen ic effects in humans has been done. In several animal experiments, both inh ibiting and promoting effects of CLAs on atherosclerosis were found. Theref ore, an antiatherosclerotic effect can not be validated. Studies in animals have shown that CLAs lower the proportion and amount of body fat mass. Thi s effect has also been reported in humans, in whom it is less pronounced th an in animals. Moreover, there is evidence that CLAs act antidiabetogenical ly, antithrombotically and antiallergenically. The data suggest that CLAs a re a unique agent with multifunctional effects. There is strong evidence th at the biologically active CLA isomers cis-9,trans-11 and trans-10,cis-12 a ct both independently and by interaction among each other. However, knowled ge about the biochemical mechanisms of CLA is still insufficient. So far, m ost studies have been carried out in animals, particularly in growing anima ls. Further research is needed to prove the efficiency of CLAs in humans. A n enrichment of food with CLA (functional food) or CLA capsules for supplem entation should not be recommended as long as this substance group has not been subject to comprehensive toxicological studies.