The 5 Best L-Glutamine Supplements, According to Registered Dieticians

WITH ALL THE supplements on the market promising to make you stronger, faster, and healthier, you may have come across L-glutamine and wondered if it’s worth the hype. Often sold as a sports supplement, this amino acid has many potential benefits, but only if you actually need it.

“L-glutamine is considered a 'conditionally essential' amino acid, which means your body normally makes enough of it to support its needs,” says registered dietician Kristin Draayer, RDN, CPT. Glutamine is essential for immune cell function and affects muscle recovery and gut health. For most healthy adults, eating a balanced diet with adequate protein is enough to supply and produce all the glutamine your body needs.

Best L-Glutamine Supplement

“Glutamine helps your immune system function, though supplementation only truly seems to be helpful when people have very low protein intakes or when the immune system is highly stressed, such as from major infection, major surgery, burns, or certain forms of radiation,” says registered dietician Brian St. Pierre, MS, RD, CSCS, the Director of Performance Nutrition at Precision Nutrition.

While glutamine supplementation is frequently prescribed by healthcare professionals for people with high-level medical needs, it’s also frequently marketed as a supplement to aid in athletic performance or to improve and support a healthy gut.

While there’s currently no evidence that glutamine supplementation can improve athletic performance, few studies have shown that it may enhance strength recovery and decrease muscle soreness in men, says Draayer. More research is needed, as the results are not consistent.

This amino acid also plays an important role in gut health and supplementing could benefit some athletes. “Glutamine could support gastrointestinal integrity during long periods of endurance exercise, potentially reducing the risk of illness after extended endurance activity,” says Draayer, although once again, more quality research is needed.

While experts agree that most healthy people won’t see a benefit from taking L-glutamine supplements, there is the potential for some benefits for those who regularly put their bodies under maximum stress with activities such as marathons or Iron Man training. “Glutamine is likely safe for most healthy adults at doses under 40 grams per day. So, there likely is no harm in supplementing if you have the financial means to do so,” says Draayer.

What to Consider

Dose

There is not a universally accepted dose for glutamine supplementation, and excessive doses could lead to a buildup of ammonia in the body. “The appropriate dosage depends on your individual needs and why you're taking it. It's always best to consult with a doctor or dietitian before starting any new supplement to determine the right dosage for you,” says Draayer. Most L-glutamine supplements are sold in 1 to 5-gram doses.

Form

Glutamine supplements are available in capsules and liquids, but the most common form you’ll find is powder, which can then be mixed with water before taking. “The best form comes down to preference and affordability,” advises Draayer.

Certifications and Quality

One of the most important factors to consider when choosing an L-glutamine supplement is the quality. Supplements are not regulated by the FDA, so trusting that what the package says is exactly what it contains is crucial for safety and effectiveness. Look for third-party verification certifications on the label, such as USP, NSF, or Informed Choice Certified.

How We Selected

To find the best L-glutamine supplements available, we spoke to the experts and reviewed a dozen popular supplements. We checked for third-party verification, ingredients, dose, certifications, price, and reviews. All of the products on our list have third-party verification and certifications by either USP, NSF, or Informed Choice to assure purity and potency. Keep reading to find the best L-glutamine supplement for your needs.