The Benefits Of L-Glutamine & When You Should Be Taking It

L-Glutamine is produced by the body and available in everyday foods, but is also a popular supplement due to its potential health and performance benefits. Glutamine exists in two different forms, L-glutamine and D-glutamine, which only vary in molecular structure. In this article we’ll be focusing on the specific health benefits and side effects of L-glutamine.


What is L-Glutamine? 

L-Glutamine is an amino acid (a building block of protein). Amino acids and proteins play many vital roles in our body. Specifically, glutamine helps with the transport of carbon and nitrogen (used for cell division and growth) in our bodies and plays roles in neural function, intestinal function, and boosting our immune system.

It’s made by the body in our muscle tissue and is therefore considered “non-essential”. This means that we don’t have to strictly consume it from our diet. However, when our body is under physical (metabolic) stress, it may require more glutamine than it makes on its own.

This need for additional glutamine, when our body is using it in higher amounts, supports the argument that L-glutamine is actually “conditionally essential” — meaning there are times when it’s necessary to consume more than what our body produces.

It makes sense that making our muscles work hard would demand more L-glutamine — since they’re responsible for creating it in the body. Instances during which our body comes under stress means it requires additional glutamine. These include severe illness and exercise. 

The fact that L-glutamine is made by our muscles, is common in our diet, and circulates in our blood makes pinpointing its effects challenging, but it’s clear that it’s used by the body both during exercise and recovery from serious illness.


Food Sources 

Dietary sources of L-glutamine include a variety of foods, from animal products like eggs and beef to vegetable sources like rice or corn. Due to this wide availability in food, following a healthy diet can provide adequate L-glutamine for most people. However, during exercise, L-glutamine production changes based on the type and intensity of activity.

Because L-glutamine is crucial for muscle building, increasing our levels via supplementation after exercise can be beneficial. L-glutamine supplementation may have a greater benefit for those who have less protein in their diets, like vegans or vegetarians. This is because they may naturally have less of this amino acid. 

Many sports supplements are targeted towards strength training, but L-glutamine has potential benefits for both power exercise and endurance exercise.



1. Quick Recovery 

Research has shown that athletes can benefit from L-glutamine supplementation to decrease muscle soreness and improve recovery time.

This amino acid plays a crucial role in controlling glucose (energy) uptake by the muscles after exercise, which can help restore their energy stores for your next workout. When your muscles have optimal glucose stores, you perform better and take longer to fatigue. 

Long periods of strenuous training have been shown to decrease blood glutamine levels, making L-glutamine potentially a very useful supplement for your post-workout nutrition plan.


2. Increased Lean Body Mass and Power 

When combined with creatine, L-glutamine supplementation has been shown to increase lean body mass and power with endurance exercise.

Studies have shown additional potential benefits, such as: 

  • Limited strength loss and reduced muscle soreness
  • Feeling less fatigued
  • Longer time until exhaustion in endurance exercise


3. Weight Loss 

Coupled with increased body mass often comes weight loss — muscle tissue burns more than fat tissue, and increases your metabolism over time. Diets high in protein and amino acids like glutamine are more filling because they slow down digestion and signal to your brain that you are full – potentially reducing overall calorie intake.  

Glutamine has also been shown to help with blood sugar regulation and prevention of obesity after consistent supplementation. 


4. Boost in Immunity 

Athletes who follow intense training schedules tend to have weakened immune systems due to the constant physical stress of high-intensity exercise. 

L-glutamine is actually used to help the immune system of critically ill patients in hospital, due to its protective effect on cells in our immune system.

Research shows that L-glutamine plays a role in both immune cell production (having enough to fight off germs) and the gut’s function as a physical barrier to infection. For these reasons, there may be a potential benefit to your immune system from an L-glutamine supplement as well.



Intakes of 20-30g of glutamine or 0.65g/kg of body mass have been used in research studies and not shown any ill effects in short term use. However, you likely only need 3-5 grams daily to meet your body’s needs.


Because glutamine has shown to be in lower concentrations after intense training sessions, it’s essential to take it after your workout to help your muscles to rebuild and grow.

It can be taken on its own or as part of your post-workout protein shake since protein is another key for muscle recovery and building. L-glutamine’s role in controlling glucose (energy) usage during workouts means it can be useful to take it before a workout instead.


Potential Side Effects 

 Dizziness was listed of a side effect in a research participant taking 25 grams per day, and went away when the dosage was decreased.

There are limited potential side effects of taking L-glutamine, as it’s both made by the body and present in many foods. However, long term supplement use of glutamine may have impacts that we don’t fully understand. Amino acids like glutamine are transported through the body by specific systems, and often several amino acids compete for the same transporters. If there is a constant surplus of glutamine, it may be more difficult for the body to adequately use competing amino acids.

If you’re unsure about the potential side effects L-glutamine might have on you, always talk to your GP before taking them. 


Take Home Message 

L-glutamine is an important amino acid that plays many roles in our bodies regardless of our level of exercise. However, the stress that exercise puts on our body can deplete our L-glutamine levels, making it a useful supplement for athletes. 

It shows many potential benefits to performance, recovery, and body mass, with limited side effects. It can also be useful to boost our immune system and help sustain adequate levels in those who follow low-protein diets.

Looking for more advice from the experts?


Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

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Claire Muszalski

Claire Muszalski

Writer and expert

Claire is a Registered Dietitian through the Academy of Nutrition and Dietetics and a board-certified Health and Wellness Coach through the International Consortium for Health and Wellness Coaching. She has a Bachelor of Science in Biology and a Master’s degree in Clinical Dietetics and Nutrition from the University of Pittsburgh.

Talking and writing about food and fitness is at the heart of Claire’s ethos as she loves to use her experience to help others meet their health and wellness goals.

Claire is also a certified indoor cycling instructor and loves the mental and physical boost she gets from regular runs and yoga classes. When she’s not keeping fit herself, she’s cheering on her hometown’s sports teams in Pittsburgh, or cooking for her family in the kitchen.

Find out more about Claire’s experience here.

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