Glutamine has been on almost every sports nutrition shelf for thirty years, with the same promise: recover faster, protect muscle, support immunity in athletes training hard. It's also one of the supplements where the gap between reputation and evidence is most imbalanced, in both directions: oversold for muscle mass, where it showed nothing, and underdosed for recovery, where it has one positive trial at a dose almost no one takes.
This page sorts what glutamine has shown in randomized trials from what it hasn't shown, gives the actual doses from studies versus the 5 g in supplement containers, including ours, and puts glutamine back in its rightful place among recovery tools, behind less marketable but far better-proven strategies.
What glutamine has shown: after intense eccentric exercise, 0.3 g per kg for 72 hours accelerates strength recovery and reduces muscle soreness (crossover randomized trial, 16 subjects). Combined with cystine, it reduces intestinal permeability markers after one hour of intense running. In women aged 60 to 80 who train, it improves knee strength.
What it hasn't shown: no effect on lean mass, strength, or protein breakdown in six weeks of weight training at 50 g per day; no effect on immunity, aerobic performance, or body composition in the meta-analysis of 25 trials. The dose that matters: positive trials are at 14 g and above per day. The 5 g in supplement containers, including ours, fall below this. What works better: total protein, sleep, post-exercise carbohydrates, creatine.
- What glutamine is, and why muscle loses it during exercise
- Recovery: the positive trial, and its limitations
- Mass and strength: the negative trial, and the meta-analysis
- Athlete immunity and gut health
- Trial doses versus the 5 g in jars, including ours
- What works better than glutamine for recovery
- Safety and precautions
- Frequently asked questions
What glutamine is, and why muscle loses it during exercise
Glutamine is the most abundant free amino acid in the blood and muscle. The body produces it itself, in large quantities, from other amino acids: it is called non-essential. It serves as a nitrogen transporter between organs, as preferred fuel for intestinal wall cells and several immune cells, and as a precursor to glutathione, the main cellular antioxidant.
It becomes conditionally essential when demand exceeds synthesis: severe burns, major surgery, sepsis, where plasma glutamine collapses and clinical nutrition supplements it. This reputation comes from intensive care medicine, transferred to sports in the 1990s with the following hypothesis: prolonged exercise lowers blood glutamine, this decrease weakens athlete immunity, and supplementation would restore it.
The hypothesis was elegant. The trials that tested it are those that follow.
Recovery: the positive trial, and its limitations
16 healthy adults, 8 men and 8 women, after 8 sets of 10 eccentric knee extensions at 125% of maximum strength: 0.3 g of glutamine per kilogram per day for 72 hours provides better strength recovery immediately after (71% versus 66%) and at 72 hours (91% versus 86%), and lower muscle soreness at 24, 48, and 72 hours (1.7 versus 2.9 on 10 at 72 hours). Effect more pronounced in men.
Legault Z et al., International Journal of Sport Nutrition and Exercise Metabolism, 2015. DOI 10.1123/ijsnem.2014-0209
This is a clean result, with solid methodology and an objective criterion, the strength torque measured by dynamometer. It says something precise: after an intense and unusual eccentric exercise, the kind that produces severe soreness, high-dose glutamine helps muscle recover its strength faster and causes less pain. Three limitations: 16 participants, only one trial of this type, and a dose of 0.3 g per kilogram, or approximately 21 g per day for 70 kg, four times the usual jar dose.
What the trial does not say: that glutamine improves progression over weeks of training. That is another question, and it has another answer.
Mass and strength: the negative trial, and the meta-analysis
31 adults aged 18 to 24, 0.9 g of glutamine per kilogram of lean mass per day (approximately 50 g) or placebo, during 6 weeks of full resistance training: squat strength and bench press, knee extension torque, lean mass, and muscle protein breakdown increase with training, with no difference between groups.
Candow DG et al., European Journal of Applied Physiology, 2001. DOI 10.1007/s00421-001-0523-y
No effect of glutamine on lean mass, body fat percentage, VO2 max, or on lymphocytes and leukocytes. Only signals: an average weight loss of 1.36 kg, a decrease in neutrophils beyond 200 mg per kilo, and higher post-exercise blood glucose with the dipeptide. Authors' conclusion: glutamine generally has no effect on immunity, aerobic performance, or body composition in athletes.
Ramezani Ahmadi A et al., Clinical Nutrition, 2019. DOI 10.1016/j.clnu.2018.05.001
The Candow trial is particularly striking because it doesn't hold back: 50 g per day for six weeks, ten times the market dose, in young adults who train seriously. If glutamine built muscle, that's where we would have seen it. We saw nothing. The meta-analysis, fifteen years later, confirms this across 25 trials. A pot of glutamine sold for muscle gain has nothing to back it up.
Glutamine is not an anabolic. It does not stimulate protein synthesis beyond what a normal protein intake does, and it does not slow down muscle breakdown in healthy athletes, as shown by the urinary marker in the Candow trial. An athlete consuming 1.6 to 2.2 g of protein per kilo already absorbs more glutamine than any supplement adds: it is abundant in all animal proteins. This is the fundamental reason why low-dose trials find nothing.
Immunity and the athlete's gut
Immunity: the 1990s hypothesis did not hold
The meta-analysis above is clear: no effect on lymphocytes or leukocytes. The drop in plasma glutamine after prolonged exercise is real, but correcting it through supplementation did not reduce infections or modify immune markers in trials. The only signal, a decrease in neutrophils beyond 200 mg per kilo, has no established clinical translation.
Gut: the lead that remains open, at high dose
16 active men, cystine and glutamine supplementation three times daily for 5 days then 30 minutes before the run: lactulose/mannitol ratio (permeability) and I-FABP (mucosal damage) significantly lower than with placebo after exercise.
Tataka Y et al., European Journal of Nutrition, 2022. DOI 10.1007/s00394-022-02806-1
352 participants, diverse populations: no overall effect of glutamine on intestinal permeability. In subgroup analysis, significant reduction only beyond 30 g per day and over short durations.
Abbasi F et al., Amino Acids, 2024. DOI 10.1007/s00726-024-03420-7
This is the most consistent use with glutamine's biology: it is fuel for intestinal cells, and prolonged exercise lowers intestinal blood flow, which produces the well-known digestive problems in endurance runners. The Tataka trial is positive, but with a cystine and glutamine combination, and the meta-analysis only finds an effect beyond 30 g per day. The lead exists. The dose is high.
Seniors: a result to confirm
44 women, active or sedentary, 30 days of glutamine or placebo: increased knee strength torque, higher average power in those who trained, better glycemic control and increased plasma antioxidant capacity in glutamine groups.
Amirato GR et al., Nutrients, 2021. DOI 10.3390/nu13031025
In seniors, glutamine synthesis and protein intake are often lower, making an effect more plausible than in well-nourished young athletes. One trial, one specific population, a result to reproduce.
Trial doses versus the 5 g in supplements, including ours
| Source | Dose per day | For 70 kg | Result |
|---|---|---|---|
| Muscle soreness and strength (Legault) | 0.3 g/kg, 72 h | 21 g | Positive |
| Mass and strength (Candow) | 0.9 g/kg of lean mass, 6 weeks | Approximately 50 g | No effect |
| Neutrophils (meta-analysis) | More than 200 mg/kg | More than 14 g | Decrease, uncertain significance |
| Intestinal permeability (meta-analysis) | More than 30 g | More than 30 g | Reduction, short duration |
| Current dietary intake | 3 to 6 g | 3 to 6 g | More with a high-protein diet |
| Our L-Glutamine | 5 g (recommended dose) | 5 g | Supplemental dose, below positive trial levels |
Honest reading: 5 g per day is a supplemental dose, of the same order as what a protein meal already provides. To reproduce the positive trial on muscle soreness, you would need four times this dose, over three days around an unusual effort. This is possible with a powder, which can be dosed to the gram and body weight, and it's impossible with capsules. This is also why we sell the powder: it allows you to follow a trial protocol. It doesn't do so at the dose written on the container.
We sell glutamine, and this page says it doesn't build muscle, that it has no effect on athlete immunity, and that the dose in the container is below that of the trials. What it has going for it: a positive trial on recovery after intense effort, a intestinal pathway for endurance, and a powder form that allows you to reach the studied doses if that's your goal. If you're looking to gain mass, the answer is elsewhere, and the next section provides it.
See L-GlutamineWhat works better than glutamine for recovery
- Total proteins, 1.6 to 2.2 g per kilogram per day spread over 3 to 5 servings. It is the best-documented nutritional lever for muscle recovery, and it contains all the glutamine a healthy athlete needs.
- Sleep, 7 to 9 hours. Protein synthesis, growth hormone secretion, and consolidation of adaptations occur at night. No powder compensates for a sleep deficit.
- Carbohydrates after long sessions, to restore glycogen and limit catabolism.
- Creatine monohydrate, 3 to 5 g per day, which has hundreds of trials on strength, power, and recovery between sets. Our article on what science proves about creatine details this level of evidence.
- Progressive overload : severe muscle soreness comes from unusual effort. A load that progresses in increments produces less soreness than any supplement can eliminate.
Glutamine comes after all this, for a specific use case, intense and unusual eccentric effort, or a lead, the endurance runner's gut, at doses that few people take. Our comparison BCAA or creatine places isolated amino acids in this hierarchy.
Safety and precautions
In trials, glutamine is very well tolerated, even at 0.9 g per kilogram for six weeks. Digestive discomfort is possible at high doses, especially in single servings. Precautions concern specific situations:
Liver or kidney disease : glutamine metabolism produces ammonia, whose elimination depends on the liver and kidneys; high doses not recommended without medical advice. Epilepsy : glutamine is the direct precursor of glutamate, an excitatory neurotransmitter; caution advised. Cancer treatment : glutamine also feeds tumor cells; oncologist's advice is essential, either way. Pregnancy and breastfeeding : insufficient data at supplement doses. Glutamate : people sensitive to dietary glutamate may be sensitive to glutamine at high doses.
Frequently asked questions
Efficacy
Does glutamine help recovery after training?
In a specific case, yes. A randomized, double-blind, crossover trial in 16 subjects shows that after intense eccentric quadriceps effort, 0.3 g of glutamine per kilogram of body weight per day for 72 hours accelerates recovery of maximum strength and reduces muscle soreness at 24, 48 and 72 hours. This is an effect on acute recovery after unusual effort, not on long-term progression, where glutamine has shown nothing.
Does glutamine build muscle?
No. The reference trial, six weeks of strength training with 0.9 g of glutamine per kilogram of lean mass per day, approximately 50 g daily, found no difference with placebo on strength, lean mass or muscle protein breakdown. The meta-analysis of 25 trials confirms the absence of effect on body composition. Glutamine is not an anabolic agent, and pages selling it for muscle gain have nothing to back them up.
Does glutamine strengthen athlete immunity?
Not according to the reference meta-analysis, which finds no overall effect on immune markers in athletes. The only signal is a decrease in neutrophil count at doses above 200 mg per kilogram, whose clinical significance is uncertain. The idea that glutamine prevents infections in overtrained athletes is a 1990s hypothesis that trials have not confirmed.
Does glutamine protect the athlete's gut?
This is the most promising avenue for long-distance runners. A randomized crossover trial in 16 men shows that a combination of cysteine and glutamine, taken for five days then before a one-hour run at 75% VO2 max, reduces markers of intestinal permeability and damage. The meta-analysis on intestinal permeability in general finds an effect only above 30 g per day. The effect exists, but the dose is high.
Is glutamine useful for seniors?
A randomized trial in women aged 60 to 80 shows that one month of glutamine combined with exercise improves knee muscle strength and power, blood glucose and antioxidant capacity, with a more marked effect in those who trained. This is a different population from young athletes, where synthetic needs are less well met, and the result deserves confirmation.
Dosages and usage
What dose of glutamine for recovery?
The positive trial on muscle soreness uses 0.3 g per kilogram per day, approximately 21 g for a 70 kg adult, for 72 hours around the effort. The meta-analysis observes an effect on neutrophils above 200 mg per kilogram, or 14 g. The 5 g per day in most products, including ours, is three to four times lower: this is a dietary supplement dose, not the dose used in trials.
When to take glutamine?
Recovery trials give it on the day of effort and the following days, in a single daily dose, without the exact timing being compared. After the session or at the next meal is the most logical choice. For the intestinal barrier, the positive trial gave it three times daily for five days then thirty minutes before the effort.
How much glutamine does food provide?
Between 3 and 6 g per day for typical nutrition, more with high protein intake. Glutamine is abundant in all animal proteins and in legumes and wheat. An athlete at 2 g of protein per kilogram already absorbs more than a 5 g container adds. This is one reason why low-dose trials show nothing.
Why is glutamine said to be conditionally essential?
Because the body produces it in sufficient quantity at rest, but certain situations exceed its synthesis capacity: severe burns, major surgery, sepsis, and to a lesser extent very prolonged effort. It is the most abundant free amino acid in blood and muscle, the main fuel for intestinal cells and several immune cells. In a healthy athlete eating enough protein, deficiency is exceptional.
Comparisons and safety
Glutamine or BCAAs for recovery?
Neither replaces sufficient total protein intake, which contains both. BCAAs have data on muscle soreness at doses of 10 to 20 g, glutamine one positive trial at 21 g. In someone already achieving 1.6 to 2.2 g of protein per kilogram, both add little. Creatine, on the other hand, has much stronger evidence on strength and recovery.
What works better than glutamine for recovery?
In order of evidence: protein intake of 1.6 to 2.2 g per kilogram spread throughout the day, seven to nine hours of sleep, carbohydrates after long sessions, and creatine monohydrate, which has hundreds of trials on strength and recovery. Glutamine comes after, for a specific use case and at a dose few people take.
Does glutamine have side effects?
It is very well tolerated in trials, including at 0.3 to 0.9 g per kilogram over several weeks. Digestive discomfort is possible at high doses. Caution is advised in cases of liver or kidney disease, where ammonia excretion from its metabolism is impaired, in cases of epilepsy, as glutamine is a precursor to glutamate, and during anticancer treatment where oncologist advice is essential. Insufficient data during pregnancy.
Glossary
- Eccentric effort
- Phase in which the muscle lengthens under load, such as the descent of a squat or downhill running. This is the phase that produces the most micro-lesions and muscle soreness, and the phase used in the positive glutamine trial.
- Torque
- Rotational force measured on an isokinetic dynamometer, an objective criterion of muscle recovery used in trials.
- Lean mass
- Body weight minus fat mass, measured by absorptiometry (DEXA). Doses in some trials are expressed per kilogram of lean mass.
- 3-methylhistidine
- Urinary marker of muscle protein breakdown, used in the Candow trial to show that glutamine does not slow catabolism.
- Intestinal permeability
- Abnormal passage of molecules through the intestinal wall, measured by the lactulose/mannitol ratio. Increases after prolonged intense exercise.
- I-FABP
- Protein released into the blood when intestinal mucosa cells are damaged; a marker of intestinal distress during exercise.
- Conditionally essential
- Nutrient that the body normally produces in sufficient quantity, but becomes limiting in certain situations of intense metabolic stress.
Sources
- Legault Z, Bagnall N, Kimmerly DS. The influence of oral L-glutamine supplementation on muscle strength recovery and soreness following unilateral knee extension eccentric exercise. Int J Sport Nutr Exerc Metab. 2015;25(5):417-426. doi.org/10.1123/ijsnem.2014-0209
- Candow DG, Chilibeck PD, Burke DG, Davison KS, Smith-Palmer T. Effect of glutamine supplementation combined with resistance training in young adults. Eur J Appl Physiol. 2001;86(2):142-149. doi.org/10.1007/s00421-001-0523-y
- Ramezani Ahmadi A, Rayyani E, Bahreini M, Mansoori A. The effect of glutamine supplementation on athletic performance, body composition, and immune function: a systematic review and a meta-analysis of clinical trials. Clin Nutr. 2019;38(3):1076-1091. doi.org/10.1016/j.clnu.2018.05.001
- Tataka Y, Haramura M, Hamada Y et al. Effects of oral cystine and glutamine on exercise-induced changes in gastrointestinal permeability and damage markers in young men. Eur J Nutr. 2022;61(5):2331-2339. doi.org/10.1007/s00394-022-02806-1
- Abbasi F, Haghighat Lari MM, Khosravi GR et al. A systematic review and meta-analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults. Amino Acids. 2024;56(1):60. doi.org/10.1007/s00726-024-03420-7
- Amirato GR, Borges JO, Marques DL et al. L-glutamine supplementation enhances strength and power of knee muscles and improves glycemia control and plasma redox balance in exercising elderly women. Nutrients. 2021;13(3):1025. doi.org/10.3390/nu13031025
- Alipanah-Moghadam R, Molazadeh L, Jafari-Suha Z et al. Glutamine supplementation can reduce some atherosclerosis markers after exhaustive exercise in young healthy males. Nutrition. 2022;94:111506. doi.org/10.1016/j.nut.2021.111506
- Ma S, Ono M, Mizugaki A et al. Cystine/glutamine mixture supplementation attenuated fatigue during endurance exercise in healthy young men by enhancing fatty acid utilization. Sports (Basel). 2022;10(10):147. doi.org/10.3390/sports10100147
