<qa>  What is the purpose of this study?Nutrition is an important part of the recovery process after having a head injury so that subjects can gain strength and fight off infection. Liquid nutrition formulas are often given to patients through a tube that has been placed into the intestines for feeding when they are unable to eat on their own. Some reports suggest that nutrition with extra amounts of the amino acid called glutamine may decrease infections and hospital stay in severely injured patients. The purpose of this study is to evaluate if giving extra amounts of an amino acid called glutamine with liquid nutrition formulas will decrease the risk of infection and length of stay in the intensive care unit after having a head injury. 