Proteins play many roles in the body; they are a component of muscle, bone, skin, and other body tissues. Other functions include providing the body with a source of energy, as a component of hemoglobin protein transports oxygen in the blood, some proteins are enzymes that function to digest food, other enzymes regulate metabolic processes such as the release of energy from nutrients and the formation of body fat, some are hormones that play a role in the regulation of body function, there are proteins that have essential roles in both fluid balance in the body and acid-base balance in the blood, there are also amino acids that function as neurotransmitters.
Each protein is made of at least one chain of linked amino acids. Which amino acids, and their order in these chains, determine the function of each protein. In building proteins, the body makes use of about 20 different amino acids. This one can be classified as either essential, nonessential, or conditionally essential (semi-essential). An essential amino acid is one that must be consumed in the diet to avoid a deficiency. This is because the body does not make these amino acids or does not make enough to meet the body’s needs.
A nonessential ones is one that the body can make enough of it to meet its needs. Others are conditionally essential (semi-essential). Such an amino acid is sometimes, but not always, required in the diet. You can read more about amino acid functions and their importance in our diet on BrainReference.com.
L-glutamine, the amino acid I will be discussing, is a conditionally essential amino acid found in protein-rich foods such as red meat, poultry, fish, and dairy products. Vegetarian sources include beans, carrots, miso, beets, wheat, and Brussels sprouts. Your body can convert another amino acid, L-glutamic acid, into L-glutamine. Generally nonessential but may become essential when the body has experienced intense physical activity, trauma, or a severe illness.
What Does L-Glutamine Do In the Body?
L-glutamine is the most abundant amino acid found in body fluids and serves as a source of energy for many different types of cells found in the body1. It is involved in nitrogen metabolism, glucose (sugar) metabolism, and has a role in the maintenance of acid-base balance.
You may be considering taking a glutamine supplement because you have read that it plays a major role in muscle growth and muscle recovery from exercise, that it reduces inflammation, supports immune system function, supports the health of the lining of the gastrointestinal tract, or has some other health-promoting activity.
The purpose of this article is to provide you with up-to-date information regarding the health impact of taking an L-glutamine supplement. It is then up to you decide whether or not you want to add this supplement to your dietary intake.
It Is Never That Easy
Whenever considering taking a supplement, you need to keep in mind that consuming a diet rich in a particular substance can impact the body in a very different way than taking a supplement of that very same substance.
In addition, when taking any amino acid/protein supplement, you should be aware of the fact that a high intake of one amino acid may inhibit the absorption of another amino acid(s). This article will focus on the dietary intake of an L-glutamine supplement that has not been prescribed by a physician.
Whenever a topic is first investigated, conclusions are often tentative and need confirmation, primarily because sample sizes are small and the duration of the study is short. I have made it a point to inform you when I have made use of such studies.
Supplements are often found either as the free amino acid or as L-alanyl-L-glutamine, glutamine attached to another amino acid2.
An analysis that combined information from many studies found evidence that, for athletes, the intake of L-glutamine supplements has little to no impact on aerobic performance, body composition (lean body mass versus fat body mass), and immune system function.
However, other, smaller studies, did find that supplements improved aerobic performance4, reduced fatigue, and promoted endurance5. There is also some evidence that L-glutamine supplements may help promote weight loss for athletes seeking to lose weight4.
While the evidence for the prevention of inflammation and muscle damage is lacking, there is evidence that L-glutamine supplementation on the order of 20–30 g per day or 0.3–0.5 g/kg body weight, taken in small doses throughout the day, does not reduce damage but can promote recovery of muscle from inflammation and damage2. In contrast, a more recent review5 found that L-glutamine supplementation can reduce both muscle injury and inflammation associated with intense aerobic activity but was unable to draw a conclusion regarding the impact of supplementation on recovery time from resistance training.
There is a tantalizing study from 20156 that suggests L-glutamine supplementation may alter the gut microbiome of overweight and obese individuals in such a way as to promote weight loss8. However, this study involved very few individuals who were studied for a short period of time, so conclusive evidence is still lacking.
There is limited evidence that individuals suffering from irritable bowel syndrome (IBS) may find that taking an L-glutamine supplement reduces some of the symptoms associated with this illness, such as loose stools and frequent bowel movements7.
As with all supplements, should you choose, after reading this article, to take an L-glutamine supplement, you should first consult with your physician, especially if you are pregnant, breastfeeding, at risk of becoming pregnant9 or taking medications such as lactulose, certain anticonvulsants, and certain chemotherapy drugs10.
As the body converts glutamine into ammonia, excessive glutamine intake may aggravate pre-existing health issues such as liver cirrhosis and kidney disease. In addition, you should be aware that L-glutamine supplements have been associated with side effects such as, but not limited to, abdominal pain, nausea, constipation, headache, pain in the arms, hands, feet, and legs9. While under some circumstances, professional athletes may benefit from taking a dietary supplement, the benefit to the non-professional athlete is questionable.