This study is being done to find out if giving a supplement called glutamine will help children with sickle cell anemia by lowering their energy needs and improving their growth and strength. Children will be randomly assigned (like a flip of a coin) to one of two groups. One group will take glutamine and one group will take a placebo (a protein mixture that looks like glutamine but may not have the same effect in the body). No one will know which group is taking which supplement until the study has been completed. Children will be in the study for 12 months.