If you took a poll of the people in your gym and asked them which supplements they use the most, among the usual suspects like protein powder and pre-workout, there’s a good chance that you’d probably run into “glutamine” being cited again and again.
In fact, a 2016 study reported that about one in four athletes reports using supplemental glutamine!
Supplemental glutamine is a popular dietary supplement taken by gym buffs in an effort to spur on the muscle recovery process and ultimately help with making gains after a good workout. However, those claims don’t actually seem to hold their weight when you take a closer look at the research.
So what’s the deal with glutamine supplementation? … and is there any reason to be adding it to your supplement stack at all?
Spoiler alert: there really isn’t any evidence to say that glutamine supplementation is definitively beneficial, either for muscle growth or gut health, in otherwise healthy populations.
What is glutamine?
L-glutamine (commonly referred to as simply “glutamine”) is an amino acid, aka one of the building blocks of protein molecules that we talk about so often in the fitness scene. As a matter of fact, it’s the most abundant amino acid in your body!
Your body makes ample amounts of glutamine on its own. However, it’s also found in most protein sources like meat, seafood, whey, and plant-based protein sources.
So what is glutamine good for?
As its most abundant amino acid, glutamine plays a huge variety of roles in your body, including:
- Facilitating brain neurotransmission, aka communication between your brain cells, by acting as a precursor to neurotransmitter amino acids
- Maintaining acid-base pH balance in your kidneys by flushing out excess amounts of the waste product ammonia
- Protecting your gut’s immune system by maintaining your intestinal cell integrity and protecting from inflammation (we’ll cover this point more in-depth in a moment.)
- And yes, glutamine also plays a role in building your muscles!
What does glutamine do for muscles?
Glutamine is the most abundant amino acid in skeletal muscle, making up ~40-60% of total free amino acids. Therefore, glutamine, like many other amino acids, is a critical component of the architecture of our muscles. Since glutamine is the most prevalent amino acid, some people recommend that you supplement with glutamine in order to help you recover better following exercise and help you build more muscle.
But despite the fact that glutamine is absolutely a crucial element for building and maintaining your muscles, this doesn’t mean that those glutamine supplements are doing what you might think based on their marketing claims.
Using supplemental glutamine for muscle growth: is there any reasoning behind it?
No. If you’re a healthy adult who is already getting enough protein from other sources, there is no proven reason to add a glutamine supplement on top of it.
Remember, L-glutamine is the most abundant amino acid. This means that it’s found so frequently in foods that contain protein that it’s highly unlikely you’re not meeting your glutamine needs from diet alone.
Furthermore, there just isn’t any definitive proof that adding more isolated glutamine to your diet does anything real for your fitness journey. In fact, evidence suggests that it doesn’t really do anything: for example, a study from 2001 found that glutamine supplementation had no significant effects on either muscle performance, body composition, or muscle protein degradation in young healthy adults who performed resistance training.
So why do supplement companies sell glutamine in the first place?
Unfortunately, this mostly comes down to the typical misleading marketing practices of the supplement industry.
There is some clinical evidence that shows a benefit from glutamine supplementation in special circumstances, such as individuals with certain diseases as well as the elderly. Some brands will cite these studies as "evidence" for glutamine benefits, without being transparent about the context of the data.
Overall, it’s likely that these populations do not consume adequate protein in general and are nutrient deficient. Therefore, supplementing glutamine may show certain benefits. But we would be hard pressed to find evidence that glutamine is more beneficial than simply increasing total protein intake, even in these populations.
In other words, there aren’t any studies that show there’s any benefit in taking glutamine among normal healthy adults.
If you’re a healthy adult who is getting enough protein from your diet, adding more glutamine is not going to speed up recovery or do anything for your muscle growth.
Glutamine and gut health
Now let’s talk about one of the other common uses of glutamine: to support gut health.
Gut health is definitely having its moment in the spotlight these days -- and for good reason! Your gut (aka your digestive tract) has a huge influence on everything from your metabolism to your immune system.
To really understand the role your gut plays here, it’s important to understand the concept of your intestinal barrier. The cells in your gastrointestinal tract are semi-permeable: in other words, nutrients and other compounds can pass from your gut and into your bloodstream and vice-versa. Under normal circumstances, this process is strictly controlled and necessary -- it’s how all those nutrients from your food get distributed through your body, after all!
But under certain circumstances, your gut lining can be “leaky” and allow for microbes and other inappropriate substances to pass through your gut lining, triggering inflammation and other health concerns. This has been linked to several gut issues including inflammatory diseases like Crohn’s and IBD.
So where does glutamine come into play? Remember, earlier we talked briefly about how one of the main roles of glutamine in the body is to maintain the integrity of your intestinal lining. So it makes sense that some people draw a connection between glutamine supplementation and improved gut health.
There are also a couple of studies that seem to support this hypothesis. Importantly, many of these studies were conducted on animal test subjects. For example:
- A 2014 study administered glutamine supplementation to mice with induced colitis (inflammation of the intestines). When compared to a control group of mice that were not given glutamine supplementation, the researchers found evidence of reduced inflammatory reactions in the mice that were given glutamine.
- A similar study was conducted on rats with induced colitis. Researchers here found that inflammatory markers were lower in rats that were administered glutamine, and that these rats also showed lower incidences of bacterial translocation than the control group.
However, it’s important to remember that animal study subjects are not representative of humans. And when you look at similar research conducted on human subjects, the evidence is much less convincing.
There are certainly some studies that showed a relationship between glutamine supplementation and improved intestinal health in certain populations. Take this systematic review, for example, which assessed several studies and found benefits in glutamine supplementation in critically ill patients and trauma patients. Or look at this study, which found that administering glutamine supplementation to patients with Crohn’s disease was linked to improved intestinal permeability.
But this isn’t enough to say that glutamine supplementation definitely improves gut health, especially when there are also studies that actually seem to counter those previous findings. For example, a trial on children with Crohn’s disease found that there was no significant advantage in giving those kids diets enriched with glutamine versus low-glutamine diets. There are also studies that seem to suggest that glutamine supplementation did not seem to help protect the immune systems of critically ill patients.
So all of these conflicting findings ultimately show one thing: while glutamine supplementation may help the gut health of certain populations, there isn't enough evidence to suggest that it’s a cure-all for everyone’s inflammatory gut issues.
The bottom line: you don’t need glutamine for muscle growth or recovery (at least, not in an isolated supplemental form)
Yes, glutamine is a necessary component for your muscle growth. Glutamine supplementation, however, is not.
Glutamine is already present in large amounts in the most common protein sources. So if you’re a healthy adult who is consuming adequate amounts of protein, there’s no good reason to add extra glutamine into the mix. There’s no evidence that this isolated amino acid on its own is going to do anything extra, even if it’s in high amounts.
And if you are struggling to make gains, a better, clinically proven alternative is to simply increase your overall protein intake. You’ll get ample amounts of glutamine this way, and you won’t need to waste your money on a supplement that has no real evidence to back it.