Rationale: It is well known that insulin resistance occurs after mediocre and intensive surgery, such as colon cancer surgery. Disturbances in insulin action negatively affect the postoperative recovery, either by prolonging the capacity of the body to regain normal function, or by increasing the metabolic stress and the risk for complications. Several studies have shown that focusing therapies on improving insulin resistance is successful. Experimental studies have shown that antioxidant agents, like glutamine (a precursor of glutathione), improve insulin sensitivity. The hypothesis of this study is that perioperative parenteral or enteral administration of glutamine, given as the dipeptide alanyl-glutamine, will reduce or prevent postoperative insulin resistance in colon cancer patients. The study will also be focused on the different routes of administration, because of the expected differential metabolic effects.