A randomized, double blind prospective study made on surgical patients who required parenteral nutrition during a 10-day period, with complete fasting. The patients were required to show a normal hepatic function measured by gamma-GT, alkaline phosphatase (FA), normal bilirubin and ALT. The evolution of the cholestasis parameters was observed on days 0, 1, 3, 8 and 10. An increase in gamma-GT was observed in the groups. This was much greater in the group with LCT (p<0.005) on the tenth day than in the MCT/LCT group. FA increased only in the LCT group, and was statistically significant (p<0.001) on the tenth day compared with the MCT/LCT group.