Glutamine is one of the most popular ingredients in bodybuilding supplements today, so the title of this article may seem surprising. Not to worry though, we stand by it…
As it turns out, Glutamine is actually one of the most exaggerated bodybuilding supplements out there. The majority of the claims surrounding Glutamine (mostly made by supplement companies who sell Glutamine) are unsubstantiated by science and, in some cases, have actually been proven to be false.
Let’s explore the research pertaining to some of these claims…
Muscle Protein Synthesis
In vitro, Glutamine has been shown to reduce Leucine oxidation rates and increase Leucine deposition in muscle tissue, effectively allowing Leucine to function more efficiently. That is, Glutamine may allow for Leucine to induce more muscle protein synthesis and be subject to less breakdown.
Similar findings have been obtained in research using mice, indicating that Glutamine supplementation may contribute to muscle protein synthesis.
This all sounds great, except that Glutamine has failed in multiple human studies to confirm the results of in vitro studies.
A study published in the European Journal Of Applied Physiology (2001) found that “glutamine supplementation during resistance training has no significant effect on muscle performance, body composition or muscle protein degradation”.
A later study published in the Journal of Strength And Conditioning Research (2003) found no additional increase in muscle protein synthesis or strength when Glutamine was combined with Creatine or Carbohydrates in resistance trained subjects.
In fact, the only circumstance under which Glutamine has been shown to improve muscle protein synthesis in human subjects is when those subjects were ill and experiencing heightened muscular wasting.
In other words, Glutamine will not help you build muscle unless you are suffering from some sort of muscle-wasting disease or condition.
Strength And Endurance
Given that Glutamine has failed to induce any sort of additioal muscle growth in the studies referenced above, it makes sense that it has also failed to increase strength when measured. You can’t increases your strength without building muscle. Generally speaking, supplements that increase strength also increase muscle mass.
There are some supplements, such as Alpha GPC, which can increase power output and muscular force without influencing muscle protein synthesis rates at all, but that’s rare. For the most part, muscle builders ARE strenght builders.
When it comes to endurance, there is some evidence to suggest that Glutamine is useful, but only in long-duration endurance exercise. When it comes to resistance training, however, there is no evidence to suggest that Glutamine is in any way favorable.
Glutamine And Immune Suppression
Most supplement companies have begun to abandon the notion that Glutamine if effective muscle builder (some still make this claim though). After all, there’s enough evidence to conclude that it doesn’t have any sort of significant impact on muscle protein synthesis over time. Now the most common claim attached to Glutamine is that it can help prevent overtraining by preventing the exercise-induced decline in Glutamine.
While it is true that Glutamine levels may be depleted by rigorous, long-term exercise (such as marathon running), short-term exercise (resistance training, sprinting, etc.) has actually been shown to increase Glutamine levels, not decrease them.
To be clear, Glutamine may be useful for those who engage in long-duration exercise such as marathon running, but is unlikely to do anything if you lift weights for an hour or so as Glutamine levels don’t start to decline until a couple hours into the workout.
The Bottom Line On Glutamine
Glutamine is still one of the most popular bodybuilding supplements today, but as the research has evolved, it’s popularity has become less and less warranted. Glutamine supplementation is ineffective for increasing strength and muscle mass as well as preserving immune function in resistance training.
To be clear, Glutamine itself is required for many bodily functions and we can’t live without it. It’s just that, as a supplement, Glutamine is pretty useless.
- Griffiths, Richard D. “Outcome of critically ill patients after supplementation with glutamine.” Nutrition 13.7 (1997): 752-754.
- Lehmkuhl, Mark, et al. “The effects of 8 weeks of creatine monohydrate and glutamine supplementation on body composition and performance measures.” The Journal of Strength & Conditioning Research 17.3 (2003): 425-438.
- Candow, Darren G., et al. “Effect of glutamine supplementation combined with resistance training in young adults.” European journal of applied physiology 86.2 (2001): 142-149.
- Cury-Boaventura, Maria Fernanda, et al. “Effects of exercise on leukocyte death: prevention by hydrolyzed whey protein enriched with glutamine dipeptide.” European journal of applied physiology 103.3 (2008): 289-294.
- Parry-Billings, M. A. R. K., et al. “Plasma amino acid concentrations in the overtraining syndrome: possible effects on the immune system.” Medicine and science in sports and exercise 24.12 (1992): 1353-1358.