Amino acids, as any good gymrat knows, are divided into two classes — essential and non-essential. Essential amino acids (of which there are nine) include leucine, isoleucine, valine, histidine, lysine, methionine, phenylalanine, threonine and tryptophan. These aminos help your body grow, recover, and function properly, and they cannot be synthesized by your body. They must be accessed via diet. The first three aminos in the list — leucine, isoleucine, and valine — are crucial for supporting protein synthesis, muscle repair, energy production and the regulation of blood sugar levels, among other tasks.
And then there are the non-essential amino acids, which also help your body thrive and function, but can be produced by your body on its own. There are eleven of these and one is glutamine.
Aha, you may be thinking, it looks like we've just answered the question at the top of this article. If glutamine -- the most abundant free amino acid in the body -- is a non-essential amino, why do I need to supplement with it? Let's take a closer look at what the science has to say.
What Does Glutamine Do?
Glutamine is an amino acid synthesized from glutamic acid via the glutamine synthase enzyme, and is important for supplying nitrogen and carbon to the cells of the body. It provides important immune function support, has been linked to gastrointestinal health, and helps to combat muscle breakdown after high-intensity exercise by supporting protein synthesis and nitrogen retention. Glutamine also supports muscle hydration, which improves endurance.
Sounds good, right? But what about that "non-essential" tag? The truth is, glutamine is more accurately described as a "conditionally essential" amino acid. That is, under normal conditions, when you're healthy and at rest, your body produces all it needs. However, at times when you're under stress -- when your immune system is under attack or during and after intense exercise -- glutamine levels can be depleted. This is why, for instance, doctors will prescribe glutamine for bedridden patients or for patients with immune-deficiency disorders. Your body's capacity to generate L-glutamine can also decrease with age, which in turn may be a factor in age-related decreases in muscle strength.
But what about high-intensity training? Here, too, short-term decreases in glutamine levels can manifest themselves, with levels of cellular glutamine dropping by as much as 50% and plasma levels of glutamine declining by up to 30%. These outcomes can lead to your body breaking down muscle tissue for energy rather than utilizing carbohydrates.
The Science Behind Glutamine Supplementation
Currently, researchers are divided on the necessity of glutamine supplementation, and ongoing study is underway. However, there is science to support its efficacy. In a study published in 2015 in the International Journal of Sport Nutrition and Exercise Metabolism, researchers investigated the effects of L-glutamine supplementation on quadriceps muscle strength and soreness ratings following eccentric exercise. In the double-blind, randomized, placebo-controlled crossover study, 16 healthy participants ingested either placebo maltodextrin or L-glutamine once per day over 72 hours and then had their knee extensor peak torque and markers of muscle soreness measured before and immediately following. The researchers found that "the L-glutamine supplementation resulted in faster recovery of peak torque and diminished muscle soreness following eccentric exercise."
In another study, published in the American Journal of Clinical Nutrition, nine healthy subjects were administered two grams of glutamine over a 20-minute period 45 minutes after a light breakfast. Subsequent forearm venous blood samples were obtained at zero time and at 30-minute intervals for 90 minutes and compared with time controls obtained one week earlier. Eight of nine subjects appeared to respond to the oral glutamine load with an increase in plasma glutamine at 30 and 60 minutes before returning to the control value at 90 minutes. Ninety minutes after the glutamine administration load both plasma bicarbonate concentration and circulating plasma growth hormone concentration were elevated. The researchers concluded that a small oral glutamine load may be capable of elevating alkaline reserves as well as plasma growth hormone.
Finally, glutamine supplementation may help endurance athletes reduce the risk of infections after participating in prolonged, strenuous exercise. In a study published in the European Journal of Applied Physiology and Occupational Physiology, researchers theorized that "the level of plasma glutamine, an important fuel for cells of the immune system, is decreased in athletes after endurance exercise; this may be partly responsible for the apparent immunosuppression which occurs in these individuals." The researchers gave athletes participating in different types of exercise two drinks, containing either glutamine or placebo immediately after and two hours after exercise. The athletes subsequently completed questionnaires about the incidence of infections during the 7 days following the exercise. The percentage of athletes reporting no infections was considerably higher in the glutamine group than in the placebo group.
Is glutamine supplementation for you? It should be noted that many whole-food sources contain abundant amounts of glutamine, including beef, poultry, fish and eggs. Many protein formulas and mass builders -- such as BioQuest's ultra-rapid-action super-premium mass builder MyoZene -- also contain added glutamine content. As for glutamine-specific supplementation, a general consensus exists for ingestion of between two to 5 grams twice daily, and up to ten grams daily for power athletes. While considerably more study is warranted to determine the exact nature and extent of the benefits associated with glutamine supplementation, this versatile amino acid certainly has a role to play in your fitness regimen and overall wellness.
The Influence of Oral L-Glutamine Supplementation on Muscle Strength Recovery and Soreness Following Unilateral Knee Extension Eccentric Exercise. Legault Z1, Bagnall N, Kimmerly DS. Int J Sport Nutr Exerc Metab. 2015 Oct;25(5):417-26.
Increased plasma bicarbonate and growth hormone after an oral glutamine load. Welbourne TC1. Am J Clin Nutr. 1995 May;61(5):1058-61.
Does glutamine have a role in reducing infections in athletes? Castell LM1, Poortmans JR, Newsholme EA. Eur J Appl Physiol Occup Physiol. 1996;73(5):488-90.
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