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What is L-Glutamine? Its Benefits and Side effects

What is L-Glutamine? Its Benefits and Side effects

What is L-Glutamine

Anyone who’s only just heard of L-Glutamine will, quite reasonably, have questions.

What does it do? Why bother taking it? What are the side effects? 

What does the “L” mean? Is there another kind? What do the other kinds do? Etc, etc.

And then some people have heard of it in relation to a specific health condition or health objective they have. Their questions will be more poignant, because they have a specific problem to solve.

Here are the more common questions posed by people new to L-Glutamine, and some answers:

How is L-Glutamine made? How does L-Glutamine work? What does it do?


L-Glutamine is an amino acid. 

It is, in fact, the most plentiful amino acid in the human body. (There are 20.) It is one of the building blocks of all proteins in your body. And there’s even evidence to suggest that it’s conditionally essential, i.e. when you’re critically ill, a ready supply of L-Glutamine will help keep you alive.

Crazy fact: The human body produces it naturally. And consumes it naturally. (So do most living creatures.) You couldn’t stop producing (and consuming) it if you tried.

Best way to think of L-Glutamine is as bricks used to build the house you live in. 

The arrangement and distribution of bricks can change to build different house designs, for different purposes. Proteins are the walls and trusses. L-Glutamine is one of the brick types in the wall.

But your house is under constant construction and re-construction. Hence it needs a ready supply of bricks. 

There’s a brick kiln on-site, churning out bricks. 

That’s your body manufacturing L-Glutamine. But the demand for bricks rises and falls over time. When you’re sick or injured, for instance, your body needs to rebuild quickly, so the demand for bricks rises. Your onsite kiln can’t keep up, so you have to make up the shortfall through your diet.

Fortunately, L-Glutamine exists in most of the foods you eat.

And it’s also easy to produce synthetically in a concentrate, from a variety of natural sources: beets, corn and shellfish are the most common.

Are L-Glutamine and Glutamine the same?

Short answer: No

Longer answer: L-Glutamine is one of two glutamines, the other being D-glutamine. 

Both have the chemical formula C5H10N2O3, but have slightly different molecular arrangements. 

Of the two, only L-Glutamine occurs plentifully in your body (and in nature). Only L-Glutamine is actually useful to you. 

D-Glutamine is both unimportant (and a slight nuisance) in your body. You have no need for it, and should not think about trying to take D-Glutamine supplements.

l Glutamine weight gain

Will L-Glutamine make me Gain weight? / Will L-Glutamine make me fat?

Short answer: No

Longer answer: If you take it while embarking on a deliberate weight gain or bodybuilding programme … yes, you will probably gain weight, and it will contribute towards that objective. The weight gained will mostly be muscle.

If you don’t take it while embarking on a deliberate weight gain or bodybuilding programme …  you will probably still gain weight, just not as much.

If you take it without any weight gain or bodybuilding programme … you might gain weight slightly, or you might not gain at all.

Supplemental L-Glutamine is an enhancer, not a cause. It isn’t a dominant driver. It accelerates the journey you’re already on, and takes you further down the road.

So could you gain weight, or get fat, while taking L-Glutamine? Yes, but the L-Glutamine won’t be to blame.

L-Glutamine benefits …

For the Gut

L-Glutamine reduces inflammation, which is behind most chronic conditions affecting large and small intestines.

It also regulates the bacterial populations in the intestines, and suppresses the growth of pathogens. 

All of this reduces the risk and complications of chronic constipation, cancer, weight gain, and inflammatory bowel conditions such as Crohn’s, ulcerative colitis, and Irritable Bowel Syndrome. 

It also counters the likelihood of so-called Leaky Gut Syndrome, in which bacteria escapes the confines of your gut to do damage elsewhere in your body..

l Glutamine side effects

For the immune system

L-Glutamine is an essential fuel source for white blood cells, T-helper cells, and specific types of cells in your intestinal system (which is itself fundamental to the immune system).

For the heart

As with inflammatory bowel diseases, inflammation is behind a lot of heart disease. Hence L-Glutamine has the same anti-inflammatory power for the heart.

For muscles

The evidence is mixed. But because of its role as a protein building-brick, L-Glutamine has been linked to improvements in muscle gain, exercise performance, and improved post-workout recovery.

For the brain

The brain doesn’t depend directly on L-Glutamine. 

It does, however, depend on Glutamate (or Glutamic acid), from which the body naturally produces L-Glutamine. Glutamate is a neurotransmitter in your brain.

Hence any prolonged deficiency of L-Glutamine will disrupt Glutamate levels, and potentially deprive the brain of an essential neurotransmitter. Brain function will be affected. 

Brain and mental health problems that have been linked with a Glutamine-Glutamate imbalance include epilepsy, bipolar disorder, schizophrenia, anxiety and depression.

L-Glutamine side effects …

Can L-Glutamine cause diarrhea, for example?

Short answer to that specific question is … Only if you took an insanely large quantity of an L-Glutamine supplement. (And if you did, diarrhea might be the least of your problems.)

As long as you take L-Glutamine in small doses, as directed, diarrhea is very unlikely. The same is true of other side effects. 

Medical literature suggests that people with histories of kidney or liver disease, Reye’s syndrome or cancer, are at higher risk of side effects, and would be well advised to consult their doctor before taking L-Glutamine long-term. (Key word there: long. Short-term use carries no additional risk.)

Why take L-Glutamine powder instead of pills or capsules?

For any of the following 3 simple reasons:

  1. You’re allergic (or have some dietary objection) to a substance in the capsule shell itself, OR …
  2. You want to be able to easily fine-tune your dosage of L-Glutamine, e.g. more than 1 capsule, but less than 2, OR …
  3. Capsules make you choke or gag. They’re unpleasant.

Which L-Glutamine is best?

It depends entirely on your preferences and priorities.

Some people don’t want to take L-Glutamine derived from corn - they’re allergic, or they don’t want to consume anything that might have been genetically-modifed. So you’d want an L-Glutamine supplement clearly labelled Corn-free, Non-GMO.

Some supplements combine L-Glutamine with other ingredients, e.g. creatine, theanine, collagen, artificial flavours, preservatives, etc. This may or may not suit you. If it does not, look for an L-Glutamine supplement labelled Single-ingredient.

If you have other dietary restrictions, e.g. halal, kosher, vegan, then you will want a supplement that clearly specifies compliance with those restrictions. Same goes for any allergies you have.