Glutamine is one of the most abundant amino acids in your body — so it’s kind of a big deal. But can you get any real benefits from additional glutamine foods or supplements?

We’re digging up the deets on all things glutamine, and if it’s worth supplementing this essential amino acid in the name of fitness.

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Glutamine is one of 20 amino acids your body needs to build proteins necessary for your organs, blood, and immune system.

Two kinds of glutamine exist: L-glutamine and D-glutamine. They’re similar, but have a different molecular arrangement.

L-glutamine is the form our body needs, and you can find it in foods and supplements. You may also see it referred to as just “glutamine” since we don’t have much use for D-glutamine.

Although our body can make L-glutamine on its own, there are times we need a boost. Illnesses or injuries are usually the culprits behind the lack of glutamine production.

Since glutamine helps form protein, it’s probably not a surprise that it’s found in pretty much all high protein foods.

Research found the following percentages of certain foods’ protein was made of L-glutamine:

  • Eggs: 4.4 percent (0.6 grams per 100 grams)
  • Beef: 4.8 percent (1.2 grams per 100 grams)
  • Skim milk: 8.1 percent (0.3 grams per 100 grams)
  • Tofu: 9.1 percent (0.6 grams per 100 grams)
  • White rice: 11.1 percent (0.3 grams per 100 grams)
  • Corn: 16.2 percent (0.4 grams per 100 grams)

A 2018 study also found a large percentage of glutamine in other plant-based food sources like whole grains and cold cereals. But, they also didn’t contain a lot of protein.

In the end, as long as you are getting enough protein in your diet, you’re also likely eating enough glutamine.

OK so you need glutamine and it’s pretty easy to get from food. But what exactly does glutamine do for your health beyond just building proteins?

Boosts immune health

Glutamine is super important for keeping your immune system going strong. It helps power immune cells like white blood cells and some intestinal cells.

According to a 2018 article, your immune system wants more glutamine during an infection or injury. If you can’t produce the amount of glutamine your body needs, your body will break down muscle (your protein stores) to release more.

This entire effect can lead to a glutamine deficiency, which can compromise your immune system even more.

Because of this, folks with intense injuries like burns are often given glutamine supplements or told to follow a high glutamine or high protein diet.

But, if you’re already healthy there’s no strong evidence taking extra glutamine offers your immune system additional support.

Aids intestinal health

Your intestines actually play a major role in immune system health. So any benefits glutamine brings to your immune system also relates to intestinal health.

A 2017 review found that glutamine plays a role in the everyday intestine function and other things like:

  • managing multiple intestinal diseases
  • increasing the number of cells in the intestinal lining
  • fending off inflammatory signals
  • protecting cells from dying

An older 2012 article also links glutamine with maintaining gut barrier function. Without a healthy gut barrier, you may be more susceptible to gastrointestinal diseases like inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and celiac disease.

Like other proteins and amino acids, glutamine comes in a powdered supplement form that is marketed for fitness.

But does it actually do anything for muscle gain and exercise performance? We’ll be honest, there’s not a lot of promising info, but here’s what the research says.

Muscle gain

Unfortunately, studies are lacking behind this topic so there’s no solid evidence glutamine supplements can actually help muscle gain or strength.

A small 2001 study found young adults taking glutamine or a placebo for 6 weeks of weight training both improved strength and muscle mass. There was basically no difference between the two groups.

New research isn’t promising either. A smaller 2021 study investigated how glutamine supplements could help the strength and power of knee muscles in elderly women. After 30 days, participants in the glutamine group had improved strength and power of knee muscles when participating in exercise.

But it’s worth noting that these elderly participants probably needed the extra glutamine because of their injury. Many athletes and healthy young adults already eat high protein diets, so it’s likely they’re getting more than enough glutamine without a supplement.

Exercise performance

Much like the studies around muscle gain, more studies (especially larger ones) need to be done in order to determine if a glutamine supplement helps exercise performance, too.

A small 2021 study of 12 professional basketball players found after 40 days, the group taking glutamine had less muscle damage and cortisol levels (which indicates stress) compared to the placebo group. This could potentially help muscle repair during recovery which can improve future exercise performance.

An older study also found glutamine supplements didn’t help muscle mass or exercise performance at all.

Another “maybe” is glutamine’s role in weight loss. Right now, we still need more information to prove glutamine supplements have legit effects on weight loss.

One 2019 systematic review and meta-analysis found that glutamine supplementation has a significant effect on weight reduction in athletes. But, it didn’t improve aerobic performance or body composition.

A different 2019 study also found that glutamine reduced waist circumference in individuals with overweight or obesity, but it didn’t change their body weight or BMI.

While there isn’t a recommended dosage, research shows that occasionally taking (as in, it shouldn’t be daily) 20 to 30 grams of glutamine seems to be OK.

But regular high intakes may lead to problems. A 2013 study found dosages around 40 grams per day could cause negative side effects.

As with any supplementation, make sure you chat with your doctor first before adding it to your routine. They can also help you determine the amount that’s safe and right for you.

If glutamine supplements are taken on the reg, it may wind up being more hurtful than helpful.

A 2013 review provides a laundry list of side effects including:

  • increased ammonia production (high levels can indicate issues with the kidneys and liver)
  • affects the distribution of other amino acids to tissues and their absorption in the gut and kidneys
  • negatively affects the immune system (only when glutamine supplements are consumed all the time)
  • may cause tumor growth with the potential of increasing cancer risk
  • withdrawal (can lead to enhanced health problems and glutamine deficiency)

Due to the many unknowns behind glutamine supplementation, it may be best to focus on getting it in through food sources.

Glutamine is one of the most abundant amino acids in your body that helps build protein.

Eating enough high protein foods will likely ensure you’re getting enough to help your immune system and intestines remain healthy.

It also comes in supplementation form, but research is iffy on whether it’s beneficial for muscle gain, athletic performance, or weight loss. Plus, it could lead to serious side effects if you take too much, too often.

If you’re still interested in taking a glutamine supplement, talk with a doctor or dietician.