as a 54 year old male that has gone from a depleted immune system (5 years ago every heavy workout would result in some sort of respiratory infection) a large waist (44 inch) and declining strength levels i can tell you that glutamine is one of the most important (no, the foundation) of my now being able to have productive workouts (strength levels are about the same as about 20 years ago) - very much stengthened immune system (i did get the flu this year but the first time in years) - a waistline that had gone fro a 44 to a 36 and decreased bodyfat levels from probably 28 percent to about 17 percent - when used at night! (that is the key - just before bedtime) glutamine (in combination with arginine, lysine, orithinine) will help with the proper sleep cycles and stimulate the body to release some natural hgh helping with the recovery process - now that is the foundation but other things are necessary but glutamine is very, very important...