Many critically ill patients are unable to provide their own nourishment. Artificial nutrition has become a routine part of critical care, and when possible, enteral is preferred over parenteral nutrition. Since its inception, many specialty enteral formulas have been developed for specific disease states. For example, higher-protein, lower-volume, higher-osmolar formulas with little to no potassium are designed for patients with kidney failure and fat-free elemental enteral formulas are often used for severe pancreatitis. One class of specialty formulas is called immunonutrition, which describe formulas designed to alter or attenuate the immune and inflammatory response seen in critical illness. These formulas may contain omega-3 fatty acids, potentially less inflammatory than the omega-6 fatty acids, essential amino acids such as arginine or glutamine, and antioxidants.