Nutrition support in the intensive care unit can impact favorably on disease severity, development of complications, modulation of the immune response, and length of stay, resulting in improved outcomes (ASPEN [American Society for Parenteral and Enteral Nutrition] 2009 guideline), but determining an individual's precise nutritional requirements remains a clinical challenge. By understanding the impact of critical illness on nutrient requirements, the dietitian can estimate needs and provide nutrition support. Monitoring tolerance to individualized nutrition support helps avoid the negative consequences of under-and overfeeding. Evidence-based nutrition support guidelines and specifically tailored care plans play a significant role in optimizing nutritional management, thus improving patient outcomes and reducing health care costs.