What are creatine and glutamine

From Ask the Doc...

Q: What do creatine and glutamine do for your body?

A: Creatine and glutamine are both nitrogen-containing compounds that are present in the body and many foods that are eaten in the average diet. Both are packaged and sold as supplements useful for enhancing muscle building in athletes and body builders.

Creatine is part of the energy-storage mechanism in muscle cells, where it is stored mainly as the chemical phosphocreatine, which is broken down into creatine and phosphate ions in the process of generating the major source of energy for intense, short-term muscle activity, adenosine triphosphate ATP. The theory favoring the use of creatine as a supplement is that by increasing the supply of creatine phosphate, ATP can be regenerated faster, thus speeding up recovery from bouts of intense, short-term exercise. It does actually work in some people, although there seems to be a genetic predisposition to effectiveness being necessary also.
Creatine use is associated with increase in muscle bulk, due to two factors: the increased amount of work allowed by quicker regeneration of ATP and the fact that creatine in muscle cells binds water, thereby physically increasing bulk. The latter effect is lost when the person stops taking creatine, and the bulk that comes from water retention is lost quickly.

Glutamine is an amino acid (protein building block) touted as a way to help reduce breakdown of muscle tissue in exercise, increase growth hormone levels, improve the immune system and help the body to respond to stress. The mechanisms for these actions are not known, and most claims for efficacy are based on the observation that with exercise glutamine levels (and, indeed, the levels of all amino acids, which are broken down to energy in the body) decrease. There are no good studies confirming the claimed effectiveness of glutamine in doing any of these things.