What You Need to Know About L-Glutamine (2024)

L-glutamine is the most plentiful amino acid in the body, involved in protein synthesis and serving as fuel for the immune system. Most people benefit from taking glutamine when their immune system is weakened or for healing a major wound like a burn.

L-glutamine is a non-essential amino acid found in food and supplements, and your body makes it on its own.

Glutamine was previously a mainstay for bodybuilders and athletes used for building muscle and reducing recovery. Taking the supplement has since been abandoned because there's no solid research backing this up.

Potential Benefits

Years ago glutamine was almost considered a conditionally essential amino acid only for those who are critically ill or injured, such as in the case of burn victims or someone who was physically stressed and at risk of muscle and tissue breakdown. In these situations, supplementing with glutamine could help reduce healing time and would be of benefit.

L-glutamine is also occasionally used to alleviate some of the side effects ofchemotherapy. It has been used for decades for health and exercise purposes, though many of these claims are unsubstantiated or exaggerated.

Immune System Support

Glutamine is important for the immune system as it helps it to function optimally. People who are critically ill or who have experienced severe physical trauma have low glutamine levels due to either a reduction in skeletal glutamine production or cells using up the body's stored glutamine more rapidly due to the trauma.

For that reason, supplementing with L-glutamine could help improve immune system function and speed recovery. Specifically for burn patients, supplementing with glutamine can help maintain healthy immune function, improve wound healing, and shorten hospital stays. An older study from India reported that the enteral delivery of L-glutamine reduced bacterial complications and hospital stays by almost 17 days compared with a control group.

For healthy individuals, the benefits of L-glutamine for immune function are lacking. In other words, if you're not immunocompromised, critically ill, or recovering from surgery, taking a daily L-glutamine supplement to improve your health is largely a waste of money.

Muscle Building, Fat Loss, and Recovery

Much to the bodybuilding community's dismay, L-glutamine does not offer the muscle-building and fat-loss benefits it was once believed to provide. Though scientists continue to look into these claims, the existing research doesn't support them.

One study examined the effects of glutamine supplementation combined with resistance training in young adults ages 18 to 24 and found no significant difference between the group who took L-glutamine and the placebo group. Both groups experienced similar muscle and strength gains.

As for weight loss, several studies support the claim that L-glutamine aids in weight reduction.

A six-week study observed 66 patients with type 2 diabetes who were split into two groups and instructed to take either 30 grams per day of L-glutamine or a placebo. The group that received L-glutamine experienced improved cardiovascular risk factors and body composition.

In addition, this study demonstrated that taking L-glutamine for four weeks also resulted in body weight and waist circumference reductions.

On the flip side, several studies have shown that glutamine supplementation does not affect weight loss and body composition. Research is ongoing to determine whether L-glutamine supplementation has positive effects for building muscle and losing weight.

All is not lost for people hoping to reap athletic benefits from L-glutamine supplementation. Several studies have shown that supplementing with L-glutamine once daily can reduce muscle recovery time and soreness after a tough workout.

In a sense, L-glutamine may help with athletic performance by delaying fatigue. If you're not fatigued, you can perform better in the gym and on the field.

Chemotherapy Side Effects

L-glutamine may play a pivotal role in improving the quality of life for cancer patients undergoing chemotherapy. Symptoms associated with chemotherapy may be less severe with a lower dose after treatment.

Chemotherapy often breaks down tissue in the intestinal lining causing mouth and throat sores, called mucositis. Some studies report reduced painful mucosal symptoms and ulceration associated with radiation and chemotherapy.

Conversely, other studies have found marginal effects of oral L-glutamine supplementation on mucositis.Though it may potentially reduce pain and discomfort, further research is needed.

Possible Side Effects

L-glutamine is safe for human consumption and does not generally cause significant side effects even at doses up to 40 grams per day. More than that and you may experience mild symptoms such as bloating, gas, nausea, dizziness, heartburn, or stomach upset.

With that said, few studies have investigated the long-term effects of L-glutamine supplements or at which doses it may cause toxicity. There is evidence, albeit slight, that L-glutamine supplements may trigger seizures in people on anti-convulsant medications. Because L-glutamine is metabolized by the liver, it may need to be avoided in people with severe liver disease.

Due to a lack of research, it is best to avoid L-glutamine during pregnancy or while breastfeeding. While L-glutamine has been used safely in infants and children, it should only be prescribed under the supervision of a pediatrician.

Dosage and Preparation

Your L-glutamine requirements are generally fulfilled through the foods you eat each day. However, 3 to 6 grams of L-glutamine daily is considered safe as a supplement.

According to an older report in Regulatory Toxicology and Pharmacology, 14 grams of supplemental L-glutamine is safe for healthy adults and no more than 0.7 grams per day per kilogram of body weight in children.

L-glutamine supplements are available in powder, oral capsule, and oral tablet form. Generally, it can be found at your local health food stores, pharmacies, grocery stores, and online.

What to Look For in L-Glutamine

Because supplement manufacturers in the United States aren't required to put their products through rigorous testing and verification processes, it can be difficult to know whether the product you're purchasing is what it says it is. For that reason, look for brands that voluntarily submit their products for inspection by an independent certifying body like the U.S. Pharmacopeia (USP), ConsumerLab.com, or NSF International.

Choosing products that display the certifications mentioned above can help ensure you're getting the highest quality and safety standards. If you are vegan or vegetarian, look for L-glutamine supplements made from fermented plant-based materials (usually beets).