What Every Man Should Know About L-Glutamine: Benefits, Sources, and Side Effects
If you’ve been optimizing your health and fitness, you've likely considered supporting your training with nutrition and supplementation. Most men look for ways to improve performance, boost results, and speed up recovery. Some supplements are common knowledge and widely used (think creatine, whey protein powder, and collagen); others are less familiar like glycine propionyl-L-carnitine and coenzyme Q10 (CoQ10). Glutamine (also known as L-glutamine) falls in the middle of the pack. It's an amino acid thought to improve aspects of training, plus benefit weight loss, skin, hair, immune system, and gut health. Ahead, learn about L-glutamine benefits, dosage guidelines, and potential side effects.
By the end of this article, you’ll have a sense of whether taking L-glutamine supplements is right for you.
Note: Talk to your doctor or dietitian before taking any new supplements.
Meet the Experts
Dr. Susan Hewlings, Ph.D., RD, vice president of Research Affairs at Radicle Science
Ana Reisdorf, MS, RD, founder of Food Trends
Florence Comite, MD, founder of the Center for Precision Medicine and Health
Jim White, CPT, RD and American Dietetic Association spokesperson
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What Is Glutamine?
Glutamine is an amino acid that helps your body deal with physical stressors and stimulates protein synthesis. Amino acids are one of those nutrition standbys that have stood the test of time. As the building blocks of proteins, amino acids are vital for muscle tissue repair and growth, among other processes. Your body can produce some of these molecules, but an essential group of nine must come from your diet.
Glutamine is non-essential, meaning your body produces it. It's the most abundant amino acid in plasma and skeletal muscles, accounting for approximately 60 percent of the total free amino acids in skeletal muscles and 20 percent of plasma amino acids, according to Dr. Susan Hewlings, Ph.D., RD, vice president of Research Affairs at Radicle Science, which is conducting some of history’s most extensive clinical trials on supplements.
“L-glutamine plays a role in cell growth, function, and repair; can be used for energy; is required to make other amino acids; helps maintain the balance of acids and bases in the body; and supports the immune and digestive systems,” says Ana Reisdorf, MS, registered dietician and brain behind the website Food Trends.
Reisdorf explains that L-glutamine is a “conditional” amino acid, meaning it's not considered an essential amino acid, but can become essential during stress or injury. When under physical stress or trauma, your body uses more glutamine, depleting its stores, according to Hewlings.
Florence Comite, MD, founder of the Center for Precision Medicine and Health, adds that during intense physical activity, the increased demand for glutamine may exceed the body's ability to supply glutamine adequately.
“It's important to get glutamine through food or supplements,” Comite says. This means that while glutamine is one of the amino acids your body produces on its own, the needs of active individuals might be higher, and getting more could translate into better L-glutamine benefits and improved health.
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Food Sources of Glutamine
Just as you can get potassium from spinach, avocado, and bananas, glutamine is found in high amounts in particular plant and animal protein-based foods. Here are some of the most common foods containing relatively high amounts of glutamine per 100 grams, according to materials published in Nutrients and stats pulled from My Food Data.
Soy protein powder isolate: 1.7g
Egg white protein powder: 1.2g
Beef: 1.2g
Shredded Parmesan cheese: 1g
Dried spirulina: 0.9g
Roasted soybeans: 0.8g
Provolone, Edam, and Gouda cheese: 0.6
Almonds, hempseed, pumpkin seeds: 0.6g
Tofu: 0.6g
Egg: 0.6g
Raw peanuts and peanut butter: 0.5g
Lamb shoulder, lean pork chops: 0.5g
Fat-free ground turkey: 0.5g
Corn: 0.4g
Skim milk: 0.3g
White rice: 0.3g
James Michelfelder
Benefits of Glutamine
Aside from the day-to-day biological needs, there are several potential L-glutamine benefits that can encourage you to get more than what your body produces. Proponents of L-glutamine claim that topping up stores with dietary and supplement sources is beneficial to weight loss and/or management; hair, skin, and gut health; immune system functioning, and more. Here, experts help break down these potential L-glutamine benefits.
Stimulates New Muscle Growth and Prevents Muscle Breakdown
Amino acids form the proteins that help build much of the body's tissue—including muscle. During intense exercise, blood and muscle levels of glutamine tend to fall, and muscle tissues break down.
Nutrient intake can reverse this effect and support muscle protein synthesis so new muscle growth occurs. "If we supplement our body with glutamine before an intense training session, we allow our body to keep a high supply of glutamine in the muscles and stop them from breaking down," explains registered dietitian and American Dietetic Association spokesperson Jim White, citing a 2018 academic article published in Nutrients. "This means the body can use the glutamine in the muscles to synthesize protein and build muscle mass."
Increases Muscle Repair and Recovery
L-glutamine assists in generating glucose—the body’s primary fuel source—for the muscles to use. It also inhibits muscle mass breakdown and improves protein synthesis. A 2015 double-blind, randomized, placebo-controlled crossover study (the gold standard, by the way) published in the International Journal of Sports Nutrition and Exercise Metabolism performed on 16 healthy volunteers suggested that l-glutamine’s anti-catabolic effects may reduce exercise-induced soreness from resistance training.
In addition to improving recovery time, glutamine also decreases muscle wasting. “High-intensity and/or exhaustive exercise, specifically weight-bearing, can cause muscle microtears; the body relies on glutamine at that time for recovery, hence its role in muscle protein synthesis and hypertrophy,” explains Comite.
Supports a Healthy Immune System and Gut
Glutamine plays a vital role in immune health—a large part of which relies on what’s going on with your gut, according to a 2017 academic review published in Nutrients. “It becomes an essential amino acid during times of illness or stress because the body uses glutamine to make new immune cells and repair any damage,” says Reisdorf.
In fact, boosting immune functioning and gut health is what glutamine is best known for, specifically for people with autoimmune diseases, according to Comite. “Glutamine is the most important amino acid to heal leaky gut syndrome, which is a major contributor to autoimmune conditions,” she says.
Leaky gut is a term used to describe an unhealthy gut lining with larger holes and cracks than a healthy one (everyone has some level of gut permeability in their intestinal lining), per Harvard Health Publishing. A “leaky” or unhealthy gut may allow partially digested food, toxins, and other nasties into underlying tissues. These foreign invaders can cause your body to react by becoming inflammatory, and the once peacefully balanced microbiome in your gut can become unbalanced, leading to digestive and immune issues.
Glutamine also supports brain health as the precursor for the neurotransmitter glutamate. “Intense physical stress, such as that experienced during strenuous exercise or illness, can lead to decreased levels of glutamine in the body; therefore, L-glutamine supplementation can help support immune function during times of stress,” Comite says.
May Help with IBS and Intestinal Symptoms
Similarly to how glutamine supports the immune system and gut, it can also be helpful for people with IBS (irritable bowel syndrome), IBD (irritable bowel disease), ulcerative colitis, and GI conditions, according to Comite.
Some experiments in animals with IBD demonstrated that glutamine supplementation can protect the intestinal mucosa, per a 2017 review published in the International Journal of Molecular Science. “The results in humans are less convincing, despite a plausible mechanism of action,” says Hewlings. Although studies may not convincingly back up glutamine supplementation for IBD, the intestine uses up about 30 percent of total glutamine consumed, which, according to Hewlings, shows it’s an essential nutrient for the gut.
In addition to quelling inflammation and other actions in the intestine, glutamine plays a crucial role in maintaining the intestinal epithelium—the gut lining, and therefore, barrier function. This means it can protect your intestinal lining and potentially improve or prevent leaky gut. However, Hewlings says the evidence isn’t clear regarding whether supplementing with glutamine will help people with these diagnosed conditions.
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May Support Weight Loss and Reduce Belly Fat
L-glutamine benefits for weight loss have mixed evidence. A 2019 study published in Nutrients on 39 overweight/obese volunteers found that supplementing with L-glutamine reduced waist circumference in people with obesity without weight loss. The same research involving rats fed chow supplemented with L-glutamine showed improved insulin sensitivity and reduced obesity and inflammatory markers. Waist circumference is one measurement that influences overall health; when higher, it typically means you're carrying around more belly fat.
Hewlings references the 2018 academic paper in the broader discussion of L-glutamine benefits for weight loss: Researchers suggest that glutamine supplementation positively impacts body composition by reducing muscle breakdown (catabolism) and promoting muscle-building (anabolic) processes. However, she adds that other studies have yet to replicate these findings consistently. “Factors such as dosage, duration of supplementation, and individual variations may contribute to the variability in results,” says Hewlings.
Comite points out that strong scientific support is not available to support taking L-glutamine to reduce belly fat or promote weight loss, but it may help support healthy weight.
“Research reveals that L-glutamine can regulate sugar levels, suggesting it may contribute to improving appetite control and potentially support weight management, but more study is needed,” she says, noting a 2020 systematic review comprising 19 studies, published in Nutrition & Metabolism.
Reisdorf suggests much of L-glutamine’s effects on metabolism and appetite may be due to it being a protein, which is well known to have an impact on increasing satiation and supporting weight loss.
Essentially, Comite explains, taking L-glutamine is likely most effective as part of an overall approach to weight management, consuming a balanced diet, participating in regular physical activity, and getting sufficient sleep.
May Play a Role in Hair Growth
Some proponents of L-glutamine say the amino acid can promote hair growth. According to Comite, there are some indirect ways in which L-glutamine might play a role in supporting healthy hair; however, hair health is influenced by a combination of factors.
“No single supplement is likely to be the magic solution for hair growth. L-glutamine is an amino acid that contributes to protein synthesis, which is important for building and repairing tissues in the body, including hair,” says Comite. However, there's no evidence that supplementing or eating foods high in glutamine will lead to longer or thicker locks.
Your best bet is to consume a balanced diet that includes adequate protein—at least 1 gram per kilogram/2.2 pounds, and up to 2 grams per kg with a strenuous exercise program, according to Comite. Also prioritize other essential nutrients to maintain healthy hair such as iron, biotin, riboflavin, and vitamins B12 and D, according to an academic review published in Dermatology and Therapy.
May Boost Skin Health
As with the quality and quantity of your hair, a clear complexion is best supported by mastering your overall lifestyle habits. This includes adequate sleep, a balanced diet, and assessing hormones, biomarkers and underlying genetic dispositions, according to Comite.
However, there may be L-glutamine skin benefits. In the aforementioned 2018 paper published in Nutrients, researchers were led to believe L-glutamine supplementation fosters protein synthesis, collagen production, and supports gut health, which affects the skin.
“A healthy gut can improve skin health and complexion, although more research is necessary to establish this connection scientifically,” says Comite.
Adding glutamine to your diet or supplement regimen could help if you have broken skin or wounds, too. L-glutamine skin benefits are a big reason why it's used in hospital settings, as it can help promote healing after surgery or traumatic injuries by aiding in tissue repair, says Reisdorf.
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Proper Dosage of Glutamine
"The body can make enough glutamine for its regular needs," says White. Because the body synthesizes it, glutamine deficiency is rare. Supplements typically suggest taking 5 grams or more for L-glutamine powder benefits. But taking high doses is not recommended due to excessive ammonia in serum, which can occur at doses as low as 0.75 grams per kilogram of body weight.
With limited research, an optimal dose for muscle-building effects is not known. What we can say is for those looking to take glutamine for muscle mass, avoid ingesting more than 40 grams daily due to an increased risk of unwanted symptoms. Some research, like a 2017 review published in Clinical Nutrition and Metabolic Care, points to 10 to 15 grams of L-glutamine powder being ideal for treating leaky gut or other digestive issues.
Supplements are available in powder or capsule form. Customers often prefer the powder form because the dosage is larger in one small scoop than in a few capsules. When mixed with liquids, glutamine powder is virtually tasteless. Note: L-glutamine powder benefits are the same as those from capsules.
Types of Glutamine Powder Supplements
There are two types of glutamine supplements—glutamine peptides and L-glutamine. L-glutamine is "free form" and not bonded to other amino acids. Most supplement takers prefer glutamine peptides, bonded to other amino acids and more stable and better assimilated by the body. However, most studies showing the benefits of glutamine supplements use L-glutamine and not peptides.
"Opt for brands that have undergone third-party assessments to confirm their purity and potency," says Hewling.
Look for seals of approval from reputable organizations like NSF International, ConsumerLab, and U.S. Pharmacopeia.
"These certifications serve as indicators of sound manufacturing practices and precise product labeling," Hewling adds. "Additionally, consider brands bearing the Clean Label Project certification, which signifies independent testing for industrial and environmental contaminants; this rigorous evaluation covers elements such as heavy metals, plasticizers, pesticide residues, and other potentially harmful substances."
Note: Reisdorf recommends the following L-glutamine supplements and to order directly from their website since third-party purveyors have been found to sell counterfeits.
Life Extension L-Glutamine
Side Effects and Risks
According to Reisdorf, L-glutamine is generally well-tolerated and considered safe, but there are a few things to consider. “For some people, it can cause side effects, including nausea, vomiting, stomach pain, gas, headache, and dizziness—these are more common at high doses,” she says.
For chronic long-term consumption, supplementation of any individual amino acid could potentially impair absorption of other amino acids, as they share transporters, and you may also impair your body’s production of glutamine, according to Hewlings.
Excessive supplementation might lead to adverse effects, according to Comite, who adds that individual reactions can vary based on factors such as health status, genetics, other medications, and supplements. Pregnant or breastfeeding women and those with liver or kidney disease should avoid supplementing with L-glutamine. For this reason, it’s best to consult a healthcare provider for advice on dosage and individual risk.
FAQ Regarding L-Glutamine
Is L-Glutamine Safe for Kidneys?
Long-term use of L-glutamine supplementation has no adverse effects in healthy individuals, per research published in the Journal of Renal Nutrition. However, it can cause kidney scarring and increase serum creatinine levels in those with diabetic nephropathy. Likewise, people with kidney disease, liver disease, or Reye’s syndrome shouldn’t supplement with L-glutamine, according to Mount Sinai. It’s also best to speak to your doctor before taking L-glutamine if you have a psychiatric disorder or are elderly.
How Fast Does L-Glutamine Work?
L-glutamine can work quickly for some concerns but may take more time for others. It also depends on how much glutamine you have stored in your body. Studies show even 3 days of once-daily supplementation are beneficial for muscle soreness and that taking L-glutamine before and after a workout can immediately help reduce inflammation and prevent immune system decline.
Does L-Glutamine Make You Hungry?
L-glutamine should not make you hungry. In fact, research shows that L-glutamine decreases the hunger hormone ghrelin, reducing hunger levels. Some research suggests that a healthy gut microbiome, such as one supported by L-glutamine, helps reduce cravings for sugary foods, which may also reduce hunger.
Can You Take Glutamine Every Day?
Research shows that taking glutamine every day is safe for healthy individuals. To keep your stores of glutamine topped up, taking glutamine each day is ideal. Make sure to speak to your health care provider before starting a new supplement or if you have any health concerns, including kidney disease or diabetes.