Glutamine for Endurance Athletes: Hype or Hoax?

glutamine for endurance

The benefits of glutamine for endurance athletes continue to evolve. Recent research has even shed light on a newly discovered benefit. Glutamine for endurance athletes is getting a lot of hype lately. But should it be, or is it just another way for supplement companies to make a buck? Keep reading to learn more about glutamine and its relation to endurance sports.

What is Glutamine?

Glutamine is an amino acid and happens to be the most abundant one found in your body. As the body is able to synthesize it, glutamine is not considered an essential amino acid. However, in some cases, your body’s glutamine requirements exceed your body’s ability to synthesize it. Thus, glutamine is considered a conditionally essential amino acid.

Glutamine plays several roles in our bodies. It is involved in cell proliferation (a fancy way to say the growth and division of cells), energy production, glycogen synthesis, ammonia buffering, and maintenance of the acid-base balance. Glutamine is found in meat and eggs, and whey and casein proteins contain large amounts of glutamines. Vegans and vegetarians with low dairy intake may require glutamine supplementation, as foods in these diets are poor sources of glutamine.

Fun fact about glutamine: there have been reports that those taking glutamine supplements have also experienced a reduction in sugar cravings! Also, though many believe the opposite, glutamine supplementation does not affect overall body composition.

Partly due to its immunomodulatory (ability to stimulate the immune system – fancy, I know) role, glutamine supplementation continues to become more popular in sports nutrition (Coqueiro et al., 2019). Glutamine is especially popular in recovery supplements. Glutamine has also been investigated for its anti-fatigue role.

Why Should I Care About Glutamine?

If you are an endurance athlete, glutamine could be an excellent supplement for you. This is especially true if you are a vegan endurance athlete. The following section will detail the benefits of glutamine for endurance athletes. As always, folks, these benefits are based on current research! If research bores you, skip this part and jump down to the list of benefits!

The Benefits of Glutamine for Endurance Athletes

Glycogen Synthesis

Coqueiro et al. (2019) completed a systematic review of relevant literature on glutamine for endurance athletes. This review included fifty-five relevant studies. According to Coqueiro et al. (2019), the research in these studies showed that glutamine supplementation improved glycogen synthesis. Additionally,  Gleeson (2008) found evidence that ingesting glutamine within the first few hours of recovery after exercise promoted glycogen synthesis.

Ammonia Accumulation

In the same literature review previously discussed (Coqueiro et al., 2019), the body of research examined also showed that glutamine supplementation reduced ammonia accumulation. In another study, Bassini-Cameron et al. (2008) found that glutamine supplementation protected athletes against increases in blood ammonia levels in both high-intensity and prolonged exercise.

Muscle Soreness & Damage

Street et al. (2011) examined the effects of glutamine supplementation on recovery following exercise over a period of 96 hours. Glutamine or placebo was ingested at 0, 24, 48, and 72 hours post-exercise. Perceived muscle soreness was measured at 0,1,24,48,72,96 hours post-exercise.  Reported muscle soreness was significantly lower over the 96 hours with glutamine supplementation than placebo. 

The second study in my research was conducted on both males and females. These participants took glutamine or placebo over a 72-hour recovery period. The results showed that those taking glutamine had reduced muscle soreness (Legault et al., 2015). Interestingly, the effect was more significant in males for reduction of muscle soreness than in females.  

Research has also been done on the relationship between muscle damage and glutamine for endurance athletes. Cordova-Martinez et al. (2021) aimed to determine if glutamine supplementation could reduce muscle damage in athletes. According to blood samples taken, glutamine did reduce the amount of muscle damage in the athletes compared to placebo. Subjects in another examination maintained better muscle mass when taking glutamine compared to placebo (Bowtell et al., 1999).

Immune System Stimulation

Glutamine supplementation has been shown to decrease the incidence of illness in endurance athletes (Castell, 2002). Researchers investigated the effects of glutamine after exhaustive exercise in various endurance athletes: middle-distance, marathon, and ultra-marathon runners, and elite rowers in training and competition (Castell & Newsholme, 1997). This study found that glutamine for endurance athletes had a beneficial effect on the level of infections after exercise. Additionally, the researchers saw the ratio of T-helper/T-suppressor cells increase. T-helper and T-suppressor cells are involved in the stimulation and regulation of the immune system.  

Exercise Recovery

Legault et al. (2015) found that muscle recovery was increased over 72 hours when taking glutamine versus placebo in a study of male and female athletes. Other researchers tested the effects of acute glutamine supplementation for endurance athletes relating to recovery after exercise. Supplementing with glutamine showed better recovery at 24, 48, and 72 hours after exercise (Waldron et al., 2018).

Gut Permeability

Glutamine is vital for maintaining a healthy gut. Rao and Samak (2011) found that low levels of glutamine concentration correlated with leaky gut and inflammation of the intestines. A recent study on the effects of glutamine supplementation and gut permeability showed promising results. Pugh et al. (2017) found that glutamine consumption reduced exercise-induced leaky-gut. Glutamine supplementation is also correlated with a reduction in inflammatory markers in the gut.

Human Growth Hormone

One of the more recent topics of research with glutamine is its possible effects on Human Growth Hormone (HGH). A recent study investigated whether an acute dose of glutamine impacted hGH levels in healthy adults, both male and female. The results showed that a single dose of glutamine was sufficient to significantly increase HGH levels compared to a placebo (Tam et al., 2020).

While this topic is gaining popularity in current research, there is also a precedent from a ways back. Welbourne (1995) found that blood samples of participants taking an oral glutamine supplement had increased blood plasma levels of HGH.

A Summary of the Benefits of Glutamine for Endurance Athletes

If you aren’t interested in the research and want to get straight to the point, this section is for you! Here is a list of the significant benefits of glutamine for endurance athletes.

  1. Increased glycogen synthesis
  2. Reduced ammonia accumulation
  3. Reduced muscle soreness and damage after exercise
  4. Improved recovery after
  5. Immune System Stimulation
  6. Reduced gut permeability
  7. Increased HGH levels

How Does All This Relate to Endurance Sports?glutamine for endurance

Now that I have discussed the benefits of glutamine let’s talk about how these benefits directly relate to endurance sports and ultra-running.

Glutamine levels are reduced after exhaustive, prolonged exercise. Much research shows that plasma glutamine concentrations are reduced in endurance athletes and athletes under chronic fatigue and overtraining syndrome. Castell (2003) found that in healthy individuals following very prolonged exercise (lasting longer than 2 hours), plasma glutamine decreased by as much as 20-30%.

Studies have also found that, in endurance athletes, glutamine deficiency is correlated with increased inflammation, oxidative stress, and impaired immune system function. Evidence also shows a reduction in stamina and overall performance.

Athletes undergoing intense/prolonged training or endurance races suffer an increased risk of infection due to impaired immune system functioning. A study performed by Casetll & Newsholme (1997) focused on athletes.    This study included questionnaires that the participants filled out. Notably, the incidence of illness for seven days after strenuous exercise was the highest in marathon and ultra-marathon runners.  /in this study, researchers found that plasma glutamine levels were decreased by approximately 20% one hour after marathon running in these athletes. Glutamine may help reduce the incidence of illness in hard-training endurance athletes.  

It is crucial to replenish muscle glycogen stores and initiate muscle tissue repair and adaptation for rapid recovery from prolonged exercise. High-intensity and prolonged exercise significantly enhance the levels of plasma ammonia, a metabolite with toxic effects on the central nervous system (Bassini-Cameron et al. l., 2008). Muscle fatigue is a side-effect of the accumulation of ammonia in the blood tissues. Furthermore, exercise-induced muscle damage is associated with impaired muscle function and delayed-onset muscle soreness.

As I discussed earlier, glutamine is an ammonia buffer, meaning that it helps maintain appropriate ammonia levels. By taking glutamine, you take a supplement that can help your muscles recover faster and reduce muscle soreness and damage.

Prolonged endurance exercise is well-known to cause a leaky gut. Leaky gut is a condition in which heat stress and reduced blood flow to the gastrointestinal tract cause intestinal cell damage that loosens tight junctions between cells, allowing for the absorption of things that are not supposed to pass through the intestinal barrier. A dysfunctional or leaky gut allows toxins and bacteria to enter the bloodstream.

As previously noted, glutamine has been shown to reduce gut permeability. Glutamine supplements may also help reduce instances of GI issues when exercising, especially during the heat. If you have read almost any of our other blogs, you already know this, but GI issues are one of the main reasons an athlete DNFs during an ultramarathon.

Lastly, Human growth hormone (HGH) is best known for influencing bone and muscle growth and body composition. I feel like I probably don’t need to go into detail about how this could benefit endurance athletes. Recent research has shown that glutamine can increase hGH. Just another checkbox checked.

As you can tell, the benefits of glutamine for endurance athletes are pretty impressive.

Is it Safe to Take glutamine?

If you plan to take glutamine, you want to know whether it is safe. Research has shown glutamine’s Observed Safe Level (OSL) to be up to 14 grams daily for normal healthy adults (Shao & Hathcock, 2008). Keep in mind that much higher levels have been tested without adverse effects and may be safe, but the data sets are limited. Therefore, the OSL is set lower by these researchers. For example, Roth (2008) found that due to the body’s high turnover rate of glutamine, high doses of up to 30 grams can be administered without side effects. Gleeson (2008) found no adverse effects of oral glutamine supplementation at 45 grams per day for six weeks.

When Should I Take Glutamine?

This is where research can divulge. Additionally, the benefits of glutamine for endurance athletes are reaped at different times of glutamine supplementation. The research on glutamine and hGH shows that these benefits are seen when taking glutamine in a fasted state. For exercise recovery, glutamine is typically taken after a workout. The same timing applies to muscle soreness and damage prevention. Most research leans toward taking glutamine immediately after exercise for the most benefits.

Terminus - The best endurance recovery supplement

Where Can I Find a High-Quality Glutamine Supplement?

You have probably already guessed it, but here at Ultraverse Supplements, we have something for you! Our recovery formula, Terminus, contains 4 grams of glutamine per serving, which science says is required to be effective. Terminus was designed to be the ULTIMATE recovery formula! Trust me. You will notice a significant difference! Before I started taking Terminus, my legs would be so sore after a run I had difficulty going up and down the stairs. Now, I no longer limp and wobble around the house after long runs.

**Use common sense, and always listen to your doctor over a blog post. They know more about your health situation than anybody behind a keyboard. If you have underlying medical conditions, always check with your doctor before starting a new supplementation routine.


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Bowtell, Joanna L., et al. “Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exercise.” Journal of Applied Physiology 86.6 (1999): 1770-1777.

Castell, L. M. (2002). Can glutamine modify the apparent immunodepression observed after prolonged, exhaustive exercise? Nutrition, 18(5), 371-375. doi:

Coqueiro, A. Y., Rogero, M. M., & Tirapegui, J. (2019). Glutamine as an anti-fatigue amino acid in sports nutrition. Nutrients, 11(4), 863. doi:10.3390/nu11040863

Córdova-Martínez, A., Caballero-García, A., Bello, H. J., Pérez-Valdecantos, D., & Roche, E. (2021). Effect of glutamine supplementation on muscular damage biomarkers in professional basketball players. Nutrients, 13(6), 2073. doi:10.3390/nu13062073

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Legault, Z., Bagnall, N., & Kimmerly, D. S. (2015). The influence of oral L-glutamine supplementation on muscle strength recovery and soreness following unilateral knee extension eccentric exercise. International Journal of Sport Nutrition and Exercise Metabolism, 25(5), 417-426. doi:10.1123/ijsnem.2014-0209 [doi]

Pugh, J. N., Sage, S., Hutson, M., Doran, D. A., Fleming, S. C., Highton, J., . . . Close, G. L. (2017). Glutamine supplementation reduces markers of intestinal permeability during running in the heat in a dose-dependent manner. European Journal of Applied Physiology, 117(12), 2569-2577. doi:10.1007/s00421-017-3744-4 [doi]

Rao, R., & Samak, G. (2012). Role of glutamine in protection of intestinal epithelial tight junctions. Journal of Epithelial Biology & Pharmacology, 5(1-), 47-54. doi:10.2174/1875044301205010047

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Shao, A., & Hathcock, J. N. (2008). Risk assessment for the amino acids taurine, L-glutamine and L-arginine. Regulatory Toxicology and Pharmacology : RTP, 50(3), 376-399. doi:10.1016/j.yrtph.2008.01.004 [doi]

Street, B., Byrne, C., & Eston, R. (2011). Glutamine supplementation in recovery from eccentric exercise attenuates strength loss and muscle soreness. Journal of Exercise Science & Fitness, 9(2), 116-122. doi:

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Waldron, M., Ralph, C., Jeffries, O., Tallent, J., Theis, N., & Patterson, S. D. (2018). The effects of acute leucine or leucine–glutamine co-ingestion on recovery from eccentrically biased exercise. Amino Acids, 50(7), 831-839. doi:10.1007/s00726-018-2565-z

Welbourne, T. C. (1995). Increased plasma bicarbonate and growth hormone after an oral glutamine load. The American Journal of Clinical Nutrition, 61(5), 1058-1061. doi:10.1093/ajcn/61.4.1058 [doi]

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