Does glutamine help your muscles recover?

Short answer

It does not build muscle or strength. Small studies found slightly less soreness, but at a large dose (about 21 g a day for a 70 kg person), and eating enough protein already gives you plenty of glutamine.

Does glutamine help your muscles recover?
'Exercise → less glutamine → supplement it → faster recovery, more muscle' — is that right?
Glutamine is an amino acid sold widely as a supplement. Long, hard training lowers glutamine in the blood, so the idea is that topping it up speeds recovery and builds more muscle. We checked this formula step by step.
Soreness dropped a little
At a large dose
16 people did a workout that makes the thighs very sore, then took glutamine or a fake pill for 3 days, swapping later. With glutamine, the soreness score at 48 hours was 2.6 versus 3.9 with the fake pill, and strength at 72 hours was back to 91% versus 86%. The dose was about 21 g a day for a 70 kg (154 lb) person.
Other studies looked similar for recovery
Most measured only a few days of recovery
23 people who took leucine plus glutamine after a jumping workout got their strength back faster than a fake pill at 48-72 hours. 12 people taking 6 g a day for 20 days had lower blood markers of muscle damage. That study did not measure performance, though.
But muscles did not grow more
Even after 6 weeks of daily use
31 people did full-body strength training for 6 weeks while taking glutamine or a fake supplement. Both groups raised their best squat by about 30% and bench press by about 14%. Lean mass (muscle and everything except fat) rose 2% and 1.7%, no difference. The dose was about 54 g a day for someone with 60 kg of lean mass.
Pooling 25 trials gave the same answer
No difference in body makeup, fitness or immunity
An analysis that pooled 25 trials found glutamine had no effect on lean mass, body fat percentage, endurance or immune cell counts. The only change was about 1.36 kg more weight loss.
It did not boost muscle building either
Adding glutamine to amino acids changed nothing
When 6 people got amino acids through a vein, their muscle-building rate rose 48%. Adding glutamine on top did not raise it any further. Glutamine went up in the blood, but not inside the muscle.
You already get a lot from food
Enough protein brings glutamine with it
People who eat a lot of protein and use protein supplements already take in plenty of glutamine. Even when blood glutamine drops after exercise, it does not fall low enough to stop immune cells from working. The usual reasons to supplement (immunity, recovery, preventing muscle loss) were not confirmed in well-fed people.
Bottom line: glutamine does not build muscle
Recovery comes from eating enough protein
Even 6 weeks of glutamine did not add muscle or strength. The study that found slightly less soreness used a large dose, about 21 g a day for a 70 kg person. Eating enough protein does the job, without buying it separately.