The care of ICU patients has seen many improvements over the years, both with regard to technical aspects and supportive measures. The first part of this book analyzes nutritional support at various levels, ranging from the cell level to the whole-body aspect; drawing on recent prospective randomized studies, the authors propose a new approach for oral, enteral and/or parenteral nutrition. The second part underlines the interference between nutrition and outcome to reach recovery, giving to this field an increased importance for better short and long term management: The best glucose control, individualized nutritional support and the avoidance of harmful interferences is extensively discussed. The final part deals with patients suffering from multi-organ failure and the need for a better understanding of the interactions between disease and nutrition. Identification of the metabolic condition of the patient, existence or not of evidence-based medicine, expert opinion, treatment opportunities and the case manager recognizing threats are all integrated to reach the appropriate decision. This last part will help the reader to untangle the complexity of the ICU patient of the 21st century and to propose a personalized nutritional support process.