L-Glutamine for Leaky Gut Repair - The Complete Low-Down According to a Functional Dietitian - Whole-istic Living

The Low-Down on L-Glutamine for Leaky Gut Repair

With chronic gut issues (like IBS and leaky gut syndrome) on the rise and becoming a modern-day epidemic, more people are turning to holistic and functional nutrition supplements such as L-glutamine for leaky gut repair.

But if L-glutamine (aka “glutamine”) is as great as the claims say it is, why are millions of people still suffering from leaky gut syndrome and actively searching for solutions?

Is it because of a lack of awareness about glutamine for leaky gut? Or perhaps people are not taking the right brand, dose, or form of glutamine? Or is L-glutamine just not as effective for gut repair as people say it is?

In my opinion as a functional dietitian and holistic nutritionist, the answers to those questions aren’t simple or straight-forward – because one size doesn’t fit all. 

In efforts to pave the way for you and others wondering whether or not ya’ll should take l-glutamine for leaky gut repair, I’m giving you my first-hand “low-down” on all things glutamine as it pertains to leaky gut in this article!

Disclaimer: This article was written for educational and informational purposes only.  This is not intended to replace or serve as medical or nutritional advice! Please consult your doctor and a functional dietitian to receive custom diet and supplement recommendations based on your individual needs.

Affiliate disclosure:  This article contains affiliate links for products that I endorse and  recommend in my practice as a functional dietitian, and/or use personally. If you make a purchase using any of my affiliate links, as an Amazon Associate and an affiliate for Starwest Botanicals, I will make a small commission at no extra cost to you!

What is L-glutamine?

L-glutamine ( “glutamine”) is one of 20 total amino acids (building blocks of protein). Glutamine is actually the most abundant and versatile amino acid in the body. (1

Glutamine is also considered a type of micronutrient (a small sized nutrient which we require in only “micro” quantities – go figure!).

In the human body, glutamine is mostly located within the tissues that make up the gut, the liver, and the muscles. It gets released into the bloodstream on an as-needed basis.

Forms of glutamine 

There are two forms of glutamine: D-glutamine and L-glutamine. (2, 3)

What differentiates D-glutamine from L-glutamine is comparable to vitamin D2 versus vitamin D3… they may look and sound very similar, but nature knows best!

  • D-glutamine, like vitamin D2, is the synthetic (made-in-a-lab) form of glutamine, while L-glutamine (like vitamin D3) is the natural, more bioavailable form of L-glutamine that the body recognizes and prefers.

For the purpose of this article as it pertains to gut health, I’m honing in on L-glutamine and disregarding D-glutamine!

Why do we need it?

Immunity and gut health

Our bodies rely on glutamine for healthy immune function and also for a healthy gut lining. This is not surprising, considering about 70% of the immune system is located in the gut! (1, 4)

Muscle strength

In the fitness world, glutamine is a popular supplement because it may help strengthen muscle and reduce muscle soreness after weight-bearing exercise. (5)

  • Some (but not all) studies are also uncovering that glutamine supplementation may also improve and enhance “strength and power” of muscles among some groups of people. But since the results of these studies are inconsistent, more research is needed in this scope. (6, 7)

Antioxidant production

Glutamine, alongside N-acetyl-cysteine (“N-A-C”), is an essential precursor to glutathione, our body’s most potent but least well-known antioxidant which is helping us to combat inflammation silently 24/7.  (Glutathione is also a micronutrient, and a conversation for another time!)

Intestinal barrier nourishment

On a cellular level, glutamine serves as a primary fuel source for our enterocytes (aka intestinal cells), supporting a healthy intestinal barrier or “gut wall”. (4, 8, 9, 10)

Glutamine in clinical practice is a hot topic of discussion, since intestinal permeability is on the rise.

Enter: leaky gut!

What is a leaky gut?

While the term sounds a bit frightening, “leaky gut” is essentially functional medicine slang for describing a gut lining that is weakened, compromised, and impaired on the cellular level (without acute, clinical-level damage).

In other words, a leaky gut is a gut lining that is overly-permeable, with poor boundaries between the outside world and the inside of your body (starting with your bloodstream).

For a bit of context, a healthy gut is supposed to be “selectively permeable” in that it’s designed to only allow healthy substances and particles  into your body, while keeping out potentially harmful substances like pesticide residues, heavy metals and other stuff that doesn’t belong in your bloodstream.

So when your gut is “leaky”, it means residues and unwanted substances (or even microbes in some cases) are seeping into your bloodstream via your intestines or colon and causing havoc.

(Learn more details about leaky gut syndrome here!)

Supplementing with L-glutamine for gut repair: what you need to know

When it comes to glutamine supplementation for leaky gut, there are lots of factors to consider.  What’s the best form? Is one brand of glutamine better than another? What kind of dose will be enough to help with leaky gut? Are there any contraindications or side effects of glutamine supplementation?

Let’s unpack each of those, one at a time!

What is the best form of glutamine?

As I mentioned earlier, the clinical studies on glutamine for gut repair reveal to us that the body (specifically your intestinal barrier) generally prefers and responds best to L-glutamine versus its synthetic counterpart (D-glutamine).

There are hundreds of different variations of L-glutamine supplements on the market, but the two main types of glutamine supplementation are available as:

  1. L-glutamine capsules (pills)
  2. L-glutamine powder

Glutamine pills vs powder: which is better?

While it’s a lot easier to pop pills, if you’re planning on taking L-glutamine to serve as a functional nutrition supplement for leaky gut repair, I recommend opting for the powder versus the pills or capsules. 

  • This is because the powdered version of glutamine is said by many holistic practitioners to be more “bioavailable” (easily absorbed and used by the body) compared to capsules.
    • While research to confirm this is lacking; it’s my anecdotal opinion based on a combination of personal experience and clinical observation over the years.

Glutamine supplements: what to look for

In the supplement industry which is still highly unregulated at this time, not all glutamine powders are created equal! 

You’ll ideally want to go with a glutamine supplement brand and product that meets the following criteria:

  1. Contains little to no additives in the form of sugars, sugar substitutes, food coloring, or chemical fillers/preservatives which could potentially have an impact on your gut or immune system, subsequently inferring with the product’s effectiveness.. (When in doubt, check the ingredient list!)
  2. Third-party tested/certified. (Most supplement companies are not third-party tested, which means their claims on the label could very well be bogus. Unfortunate but true.)
  3. Good Manufacturing Practice (GMP) certified via the National Sanitation Foundation (NSF).
  4. Non-GMO (not genetically modified).

Best L-glutamine brands and products

Below (in no particular order) are some affiliate links for my top 5 preferred glutamine supplement brands and products, which are very high quality and meet most or all of the above criteria.  Feel free to check them out!


This product also contains some helpful herbs for leaky gut such as:

  • Marshmallow root
  • Aloe vera leaf
  • Deglycerized licorice root (DGL) 
  • Slippery elm bark 

FYI:  These herbs can work great synergistically alongside L-glutamine to help support healthy mucous membranes. However, they also contain some FODMAPS which may trigger gas/bloating among some people with small intestinal bacterial overgrowth (SIBO).  If that’s the case, you may be better off trying one of the other options!

How and when to take L-glutamine for leaky gut repair

There are many possible ways to take L-glutamine, and in my anecdotal case study experience (as well as throughout my personal gut-healing journey) I’ve found that some methods are more effective and helpful than others!

Powder versus pills

As I mentioned earlier, taking L-glutamine in powder form (versus capsules) seems to deliver better, more noticeable clinical outcomes, anecdotally.  This could be because powder doesn’t need to be broken down in the gut – it goes right to the gut lining in free form.

Temperature range

Too-hot temperatures might reduce the potency of L-glutamine.

Glutamine is more stable (less likely to degrade and lose clinical potency) at cold temperatures, room-temperature or luke-warm temperatures versus at higher temperatures.  (11)

  • That said, adding your L-glutamine powder to a cup of piping hot coffee or tea (or hot lemon water) may not give you the most bang for your buck, if you’re looking to support a healthy gut!  
    • Instead, try dissolving or blending your L-glutamine powder in a cold, luke-warm, or room-temperature liquid for maximum potency.

With or without food? 

While there’s not a lot of research to back this up, anecdotally it’s often recommended to take your glutamine supplement (dissolved in a beverage of choice) ~20 to 30 minutes before a meal, or a few hours after a meal (unless it’s a soup or smoothie).

  • Taking glutamine on an empty stomach or with only small amounts of food allows for the glutamine to go directly to your intestinal cells, versus mixing in with large amounts of food particles which would delay and dilute its effects.

It’s also considered “best practice” in functional nutrition to avoid animal protein within at least 30 minutes or more of taking L-glutamine.

Either way, I understand it’s easy to over-think these things and get in the weeds about all of it. Perfectionism destroys progress! 

  •  At the end of the day, it’s better to take your glutamine supplement than to not take it (if you benefit from L-glutamine supplementation). 😉

What time of day?

Honestly, whatever time of day works best for you is the best time to take your L-glutamine supplement! 

  • For example, if you’re an avid smoothie drinker, adding a scoop of glutamine powder to your morning smoothie is an easy way to start incorporating L-glutamine into your daily routine consistently.

What’s the recommended dose of L-glutamine?

Again, to reiterate, this is NOT medical advice!  You’ll want to receive your specific recommended dose from your functional medicine doctor and/or functional dietitian.

But speaking generally, one “heaping” scoop of glutamine (providing ~3 grams per serving) dissolved in 6 to 8 oz. of water or a beverage of choice, two to three times daily, is usually helpful as a therapeutic goal dose for those who can tolerate and benefit from L-glutamine supplementation.

How much is too much?

When it comes to adding in a new supplement of any kind, but especially L-glutamine, more is not always better.  In fact, going from zero-to-sixty overnight (in efforts to speed up your healing) can actually do more harm than good!

When introducing L-glutamine into your routine, I recommend starting out small (well below the recommended dose).  From there, you should plan to increase your daily dose very slowly and gradually (over the course of a week or two), as tolerated.

Either way, it’s entirely possible to have an adverse reaction to L-glutamine, even in some cases at extremely small doses.  

  • To avoid potentially severe side effects, I would not exceed a dose of ~10 to 12 grams per day (based on my clinical judgment).  Other practitioners may agree or disagree.

When is the best time to start taking glutamine for gut repair?

I don’t recommend taking L-glutamine too early on in your gut-healing journey when your gut lining is still very “leaky” or damaged.  This is because lots of people with a damaged gut lining cannot yet process and absorb glutamine effectively.  

  • In my 10+ years of practice, I’ve unfortunately seen more adverse reactions to L-glutamine supplementation (and even bone broth and collagen peptides) than I can count!  

When NOT to take L-glutamine for gut repair (contraindications)

While the research on L-glutamine sounds shiny and promising, hold those rainbows and butterflies! Taking lots of glutamine is not always a good thing.

Taking glutamine too soon in your healing journey before your gut is ready for it (such as in many cases of IBS-D, colitis, and Crohn’s disease), you might find yourself doubled over in pain or running to the bathroom within an hour or less after each dose. 

  • Your reaction to glutamine will of course vary case-by-case, but I’m sharing this as a word of caution after observing adverse reactions to glutamine multiple times over among my clients who took glutamine, collagen, or bone broth before they were ready.

To avoid and minimize the risk of adverse effects to glutamine, if you have irritable bowel disease (IBD) or diarrhea-predominant irritable bowel syndrome (IBS-D), I recommend consulting your holistic and functional nutrition provider(s) individually versus trying to self-prescribe. 

In other cases of leaky gut that don’t include severe gut damage or diarrhea, taking a powdered version of L-glutamine in moderation consistently is more likely to be safe and helpful!

Possible side effects and adverse reactions of L-glutamine 

You’ll most likely experience side effects or adverse reactions of L-glutamine pretty sudden onset, within 30 minutes of taking it.  This is something you can and should pay attention to if you keep an IBS/leaky gut food-symptom diary.

There are also some side effects that can take place over the long-term if you’re supplementing with glutamine unnecessarily – since it breaks down into glutamate and ammonia. (12)

Below are some of the most commonly reported adverse reactions to L-glutamine based on clinical experience and clinical studies (12, 13):

  • Abdominal pain/cramping 
  • Diarrhea
  • Nausea
  • Vomiting
  • Hives
  • Rapid heartbeat
  • Muscle or joint pain
  • Headache
  • Dizziness
  • Acute-onset fatigue
  • Dry mouth
  • Runny nose
  • Neurological impairment
  • Liver damage

While this goes without saying, please contact your doctor or go to your nearest emergency room if you’re experiencing any of those adverse effects from glutamine supplementation (whether acute onset or from long-term use).

Alternatives to L-glutamine for supporting leaky gut

I’ve witnessed in my field of functional nutrition that L-glutamine is the most well-known supplement for leaky gut – but is it the most helpful and effective? Not necessarily.

Below is a list of some helpful alternatives to glutamine, which may or may not be a better fit for you on your gut-healing journey as it pertains to gut repair.

Keep in mind, this list is definitely not exhaustive – there are dozens (if not hundreds) of options out there! But I want you to have an understanding that one size does not fit all, and there are many different ways to heal.  Since your body is unique, what works for other people may not be what works best for you!

Affiliate link - SBI Protect powder for leaky gut

Affiliate link - SBI Protect capsules for leaky gut

Affiliate link - Vital Proteins Collagen Peptides powder for leaky gut

Vital Nutrients DGL Powder for Leaky Gut

Affiliate link - Pure Encapsulations brand DGL Plus capsules for leaky gut

Affiliate link - George's aloe vera leaf juice for leaky gut

Affiliate link - Kettle & Fire brand classic beef bone broth

Additional resources 

I hope you enjoyed this article and found it helpful! If you did, please feel free to share this article with someone you know who is navigating glutamine and/or leaky gut and would like some extra information. 😎

On another note, if you’re on a gut-healing journey of any kind, you may also enjoy the following articles which focus on herbal medicine and holistic/functional nutrition for leaky gut repair and digestive health:

Next steps

If you’re feeling ready to start taking action via a step-by-step roadmap, you may be a great fit for the Complete Gut Repair Roadmap Online Course which walks you step-by-step through my 6 pillars of complete gut repair.  

Final thoughts

L-glutamine for leaky gut is a hot commodity nowadays in the world of functional nutrition. This is because we know that L-glutamine plays major roles in helping to nourish and strengthen the intestinal barrier, keeping your gut healthier and your immune system more resilient.

But still, not all glutamine supplements are created equal!  A few things to keep in mind:

  • It’s best to choose a product that contains little to know chemical additives/preservatives/sweeteners, is third-party tested, GMP-certified, and non-GMO.
  • It’s better to take L-glutamine in powder form and before or between meals, at a not-too-hot temperature for optimal results.
  • A generally safe therapeutic dose of L-glutamine will range between 3 and 12 grams per day, but it’s always best to consult with your medical nutrition team 1:1 for custom guidelines to meet you where you’re at.

Glutamine isn’t for everyone, since it gets down into glutamate + ammonia which can lead to unwanted adverse side effects among people with severe leaky gut or IBD.

If you’d like to support your gut in other ways, there are lots of herbs, functional foods and nutraceuticals which can make great alternatives to glutamine for gut repair.

Last but certainly not least, it’s important to keep in mind that repairing your gut lining with the right supplementation is only ONE of six pillars of complete gut repair! You’ll also need to…

  • Get clarity on your root causes and any underlying diagnoses
  • Uncover your body’s best foods and eat them often
  • Remove and replace any offending foods that are inflaming you
  • Optimize your microbiome
  • Reset your nervous system (if you’re spending too much time in “fight or flight”)
  • Identify and remove any trapped emotions in your body
  • Maintain & sustain, rinse and repeat as needed!

To learn more about what my complete gut repair roadmap entails, make sure to check out the Complete Gut Repair Roadmap online course.

Complete Gut Repair Roadmap with Jenna Volpe - Learn More

XO – Jenna