 After surgical treatment, numerous trials using early postoperative enteral or parenteral nutritional support have been attempted, in order to reduce morbidity and mortality. Although it is difficult to compare among heterogeneous interventions, most of them have not been successful, a fact generally attributed to the timing of the intervention. On the other hand, nutrients that become conditionally essential under certain stressful circumstances, the so called nutraceuticals, have been incorporated into nutritional formulations. Both facts have prompted the idea of pre or perioperative nutrition support, using specific formulations called immune enhancing formulas, containing arginine, nucleotides, glutamine and omega3 fatty acids in varying concentrations. The provision of these nutraceuticals prior and early after the surgical, and particularly in oncologic surgery, theoretically permits to obtain adequate circulating and tissue concentrations for the moment when they are most needed. Exclusive postoperative provision of these substances would not be able to replenish depots and provide them for an adequate immune response and wound healing after surgery. However, regarding the preoperative approach, it is still not know which patients benefit more less or more severely malnourished, which specific nutrients are responsible for the positive effects, and the precise timing these nutrients should be provided. The present study aims to demonstrate that immune-enhancing formulas are superior to standard enteral products in reducing postoperative nutrition-related complications. 