Glutamine is a nonessential amino acid found in high protein foods such as beef, chicken, fish, eggs, and dairy products and in uncooked plants including cabbage, spinach and parsley.  There is no daily requirement for glutamine but the need seems to increase during medical stress.  Scientific evidence does not back glutamine’s role in reducing sugar cravings.  Glutamine’s function in metabolism is a major area of investigation, but research is mostly at the animal level.  Glutamine supplements are sometimes used to reduce alcohol craving in rehab centers, but that practice is experimental too.  Glutamine supplements are popular with body builders as explained by the Guide to Sports Medicine at About.com.