Protein builds your body, and amino acids build protein. Glutamine is the most abundant amino acid in your body. If you combined all the other amino acids in your bloodstream, glutamine would still be triple the amount. And considering how important amino acids are, that's really a big deal.

Helps build protein within your muscles
Helps prevent muscles from breaking down
Helps restore glycogen levels which increases performance
Helps boost your muscle recovery time
Helps to improve digestion/intestinal health
Help to reduce risk of upper respiratory tract infections from training and racing
The TOP benefit for ENDURANCE ATHLETES is RECOVERY!!!
L-glutamine plays a crucial role in strengthening your immune system. Your immune system is your body armor, your bullet proof vest. It keeps you healthy by defending against illness. This makes it a powerful supplement for everyone, not just athletes. When people get very sick, their glutamine levels become depleted. Numerous studies have shown that supplementing glutamine while recovering from various illnesses and surgeries actually speeds the process up. For a lot of people, overtraining is very common. When we try and follow the regimes that top athletes and bodybuilders do, we tend to overtrain.
People who don't really study and read about supplements, don't know the value and benefits of this supplement. It's not flashy or heavily marketed. It stays under the radar, but it certainly get its job done.