Glutamine: Benefits, Uses and
Side Effects
Glutamine is an important amino acid with many functions in the body.
It is a building block of protein and critical part of the immune system.
What’s more, glutamine has a special role in intestinal health.
Your body naturally produces this amino acid, and it is also found in
many foods. Yet, you may be unsure if you need extra glutamine from
supplements for optimal health.
This article explains why glutamine is important and discusses the
benefits and safety of glutamine supplements.
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What Is Glutamine?
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Glutamine is an amino acid. Amino acids are molecules that play many
roles in the body.
Their main purpose is to serve as building blocks for proteins.
Proteins are crucial to the organs. They also serve other functions, such
as transporting substances in the blood and fighting off harmful viruses
and bacteria (1).
Like many other amino acids, it exists in two different forms: Lglutamine and D-glutamine.
They are almost identical but have a slightly different molecular
arrangement (2Trusted Source).
The form found in foods and supplements is L-glutamine. Some
supplements list it as L-glutamine, but others simply use the broader
term glutamine.
While L-glutamine is used to make proteins and perform other
functions, D-glutamine appears to be relatively unimportant in living
organisms (3Trusted Source, 4Trusted Source).
L-glutamine can be produced naturally in your body. In fact, it is the
most abundant amino acid in the blood and other body fluids (5Trusted
Source, 6Trusted Source).
However, there are times when the glutamine needs of your body are
greater than its ability to produce it (7Trusted Source).
Therefore, it’s considered a conditionally essential amino acid, meaning
that it must be obtained from the diet under certain conditions, such as
injury or illness (8).
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Also, glutamine is an important molecule for the immune system and
intestinal health (9Trusted Source).
Summary Glutamine is an important amino acid. L-glutamine is the
form found in foods, supplements and the human body. It is part of
the proteins in your body and involved in immune function and
intestinal health.
It Is Found in Many Foods
Glutamine is naturally found in a variety of foods. It has been estimated
that a typical diet contains 3 to 6 grams per day, but this can vary based
on your specific diet (10).
The largest amounts are found in animal products due to their high
protein contents.
However, some plant-based foods have a greater percentage of it in their
protein.
One study used advanced lab techniques to determine how much Lglutamine is found in various foods (11Trusted Source).
The following are the percentages of protein made up of L-glutamine in
each food:
Eggs: 4.4% (0.6 g per 100 g of eggs)
Beef: 4.8% (1.2 g per 100 g of beef)
Skim milk: 8.1% (0.3 g per 100 g of milk)
Tofu: 9.1% (0.6 g per 100 g of tofu)
White rice: 11.1% (0.3 g per 100 g of rice)
Corn: 16.2% (0.4 g per 100 g of corn)
Although some plant sources, such as white rice and corn, have a large
percent of protein made up of glutamine, they have fairly low protein
contents overall (11Trusted Source, 12Trusted Source, 13Trusted Source).
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Thus, meat and other animal products are the simplest ways to get high
amounts of it.
Unfortunately, the exact glutamine content of many specific foods has
not been studied.
However, because glutamine is a necessary part of proteins, virtually any
food containing protein will contain some glutamine.
Focusing on getting enough protein in your overall diet is an easy way to
potentially increase the amount of glutamine you are consuming.
Summary
Almost any food containing protein will contain some glutamine, but
amounts vary. Animal foods are good sources due to their protein
contents. Getting enough protein in your diet can ensure you are
getting enough.
It Is Important for the Immune System
One of the most important functions of glutamine is its role in the
immune system.
It is a critical fuel source for immune cells, including white blood cells
and certain intestinal cells (14Trusted Source).
However, its blood levels can decrease due to major injuries, burns or
surgeries (15Trusted Source, 16Trusted Source).
If the body’s need for glutamine is greater than its ability to produce it,
your body may break down protein stores, such as muscle, to release
more of this amino acid (17, 18Trusted Source).
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Additionally, the function of the immune system can be compromised
when insufficient amounts of glutamine are available (17, 19Trusted
Source).
For these reasons, high-protein diets, high-glutamine diets or glutamine
supplements are often prescribed after major injuries like burns (17).
Studies have also reported that glutamine supplements may improve
health, decrease infections and lead to shorter hospital stays after
surgery (20Trusted Source, 21Trusted Source).
What’s more, they have been shown to improve survival and reduce
medical costs in critically ill patients (22Trusted Source, 23Trusted
Source).
Other studies have shown that glutamine supplements may also
improve immune function in animals infected with bacteria or viruses
(19Trusted Source, 24Trusted Source).
However, there is not strong support for benefits in healthy adults, and
the needs of these individuals may be met through diet and the body’s
natural production (25Trusted Source).
Summary Glutamine plays an important role in immune function.
However, during illness or injury, the body may not be able to
produce enough of it. Glutamine supplements may help improve
immune function and preserve protein stores in the body.
It Plays a Role in Intestinal Health
Glutamine’s immune system benefits are related to its role in intestinal
health.
In the human body, the intestines are considered the largest portion of
the immune system.
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This is because of the many intestinal cells with immune functions, as
well as the trillions of bacteria that live in your intestines and impact
your immune health (26Trusted Source).
Glutamine is an important energy source for intestinal and immune cells
(9Trusted Source, 14Trusted Source).
It also helps maintain the barrier between the inside of your intestines
and the rest of your body, thereby protecting against a leaky gut
(6Trusted Source, 27Trusted Source).
This prevents harmful bacteria or toxins from moving from your
intestines into the rest of your body (28Trusted Source).
Additionally, it is important for the normal growth and maintenance of
the cells in the intestine (6Trusted Source, 27Trusted Source).
Due to the major role of the intestines in the immune system, glutamine
may benefit your overall immune health by supporting the intestinal
cells (19Trusted Source, 26Trusted Source).
Summary Your intestines are a major part of your immune system.
Glutamine is an energy source for intestinal and immune cells. It also
helps maintain the barrier between the intestines and the rest of
your body and aids with proper growth of intestinal cells.
Effects on Muscle Gain and Exercise
Performance
Due to its role as a building block of protein, some researchers have
tested whether taking glutamine as a supplement improves muscle gain
or exercise performance.
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In one study, 31 people took either glutamine or a placebo during six
weeks of weight training (29Trusted Source).
By the end of the study, both groups showed improved muscle mass and
strength. However, there were no differences between the two groups.
Additional studies have also shown that it has no effects on muscle
mass or performance (30Trusted Source, 31Trusted Source).
However, some research has reported that glutamine supplements may
decrease muscle soreness and improve recovery after intense exercise
(32Trusted Source).
In fact, one study found that glutamine or glutamine plus carbohydrates
can help reduce a blood marker of fatigue during two hours of running
(33Trusted Source).
It has also been used to try to boost the immune function of athletes,
but results vary (34Trusted Source, 35Trusted Source, 36Trusted Source).
Other research has found that it did not improve the recovery of
carbohydrate stores (glycogen) in muscle when added to carbohydrates
and certain amino acids (37Trusted Source).
In the end, there is no evidence that these supplements provide benefits
for muscle gain or strength. There is some limited support for other
effects, but more research is needed.
It’s also important to note that many athletes have high protein intakes
in their regular diets, meaning they may be consuming large amounts of
glutamine even without supplements (38Trusted Source).
Summary There is little support for the use of glutamine
supplements for muscle gain or strength performance. However,
they may reduce fatigue or decrease muscle soreness during and
after exercise.
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Dosage, Safety and Side Effects
Since glutamine is an amino acid that is naturally produced in the body
and found in many foods, there is no concern that it’s harmful in normal
quantities.
It has been estimated that a typical diet may contain 3 to 6 grams per
day, although this amount could vary based on the types and quantities
of foods consumed (10).
Studies on glutamine supplements have used a wide variety of doses,
ranging from around 5 grams per day up to high doses of approximately
45 grams per day for six weeks (29Trusted Source).
Although no negative side effects were reported with this high dosage,
blood safety markers were not specifically examined.
Other studies have reported minimal safety concerns regarding shortterm supplementation of up to 14 grams per day (39Trusted Source).
Overall, it is believed that the short-term use of supplements is likely
safe. However, some scientists have raised concerns about their
sustained use (25Trusted Source).
Adding glutamine to a regular diet may cause a variety of changes in the
way the body absorbs and processes amino acids. Yet, the long-term
effects of these changes are unknown (25Trusted Source).
Therefore, more information is needed concerning long-term
supplementation, particularly when high doses are used.
It is possible that glutamine supplements may not have the same effects
if you eat an animal-based, high-protein diet, compared to a plantbased, lower-protein diet.
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If you follow a plant-based diet with low glutamine content, you may be
able to consume supplements while still receiving a normal daily
amount of it overall.
If you decide to take a glutamine supplement, it is probably best to start
with a conservative dose of around 5 grams per day.
Summary Intake of the glutamine found in foods, as well as the
short-term use of supplements, is safe. However, glutamine
supplements can affect how your body processes amino acids. More
studies on their long-term use are needed.
The Bottom Line
Glutamine is an amino acid that exists in two forms: L-glutamine and Dglutamine.
L-glutamine is the important form, which is produced naturally in the
body and found in many foods. It is estimated that a typical diet
contains 3 to 6 grams per day.
It provides fuel for immune and intestinal cells and helps keep the
connections in the intestines strong.
During times when your body cannot produce optimal amounts, such as
during injury or severe illness, supplementing with it may be beneficial
for your immune health and recovery.
Glutamine is also frequently used a sports supplement, but most
research does not support its effectiveness.
Supplementing appears to be safe in the short-term, but more research
is needed on its long-term effects.
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Before taking a glutamine supplement, consider whether the reason for
taking it is supported by current evidence.
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