Agents of immunonutrition (or, pharmaconutrition if you will) investigated in the critical care literature have included specific amino acids (arginine, ornithine, glutamine), varying chain lengths of fatty acids, omega-3 fatty acids, nucleotides, antioxidants, zinc, copper, selenium, and probably a hundred others. There has been a lot of interest in the use of these "pharmacologically active nutrients" to modify the immune and inflammatory responses in critical illness. The theory is that supplementing these molecules may somehow influence the behaviour of the immune system, making it work in favour of the critically ill patient. The objective is to improve wound healing, dampen the stress response to critical illness, decrease oxidative stress, and diminish the risk of infection. Unfortunately, the promises made regarding these supplements have thus far largely failed to materialise as hard outcomes. The only possible exception to this is selenium which appears to improve mortality in severe sepsis when given in large doses.