L-glutamine: The miracle cure for metabolism and intestines?

⏱ 13 min read

Have you ever heard of the remarkable health-promoting properties of L-glutamine? If you are interested in building muscle and burning fat, you may no longer be a stranger to L-glutamine. But what can the amino acid do?

Originally, L-glutamine was mainly used in the fitness industry and was used to lose weight, burn fat and build muscle. Although the amino acid is still used for this purpose today, the numerous positive effects are also noticeable in other ways. For example, L-glutamine regulates the digestive system and has proven its worth in the treatment of intestinal problems and leaky gut syndrome - the condition in which the intestines are "leaky" and therefore responsible for many serious health complaints.

But what effects and side effects can you expect when supplementing with L-glutamine? Which foods contain L-glutamine? What are the symptoms of an L-glutamine deficiency and what should you bear in mind when taking it? Find out here.

What is glutamine anyway?

Glutamine or L-glutamine is one of 20 naturally occurring semi-essential amino acids found in protein-containing foods. Semi-essential means that the body can produce it itself, but the amount it produces is not sufficient for a complete supply. A large proportion must therefore be obtained from food.

➤ Glutamine is the most abundant amino acid in the human bloodstream.

It can become an essential amino acid if a person suffers from certain diseases or muscle atrophy or does a lot of endurance sports. Supplementation with the amino acid can promote protein biosynthesis, i.e. the formation of new proteins in the cells, and balance the pH value in a natural way.

Glutamine is contained in these foods

The amino acid glutamine is found in both animal and vegetable protein sources. However, it should be noted that proteins of animal origin are generally better processed by the body than plant proteins. Doctors assume that you should consume between 3 and 6 grams of glutamine daily with food.

Glutamine-rich foods are:

• Protein
• Wheat
• Peanuts
• Soy
• Milk
• Beef
• Spirulina
• Cottage cheese
• Asparagus
• Cod
• Salmon
• Game meat
• Turkey
• Maize
• Rice

In order to absorb a sufficient amount of glutamine, it is recommended to consume at least three of the foods mentioned above per day.

What are the symptoms of L-glutamine deficiency?

Vegetarians and vegans in particular can be affected by a glutamine deficiency, as the body can process and absorb animal proteins more easily than plant proteins. As people who eat a mainly plant-based diet consume little or no animal protein, an additional intake of L-glutamine can be beneficial.

➤ Around 60 % of skeletal muscle is made up of glutamine

However, an increased need can also affect people after surgery, illness or during sepsis. Glutamine supplementation is used in many different clinical applications for patients with trauma, burns and post-injury . During metabolic stress, i.e. after injury or illness, more glutamine must be produced and released to meet metabolic needs. A lack of glutamine can therefore have serious consequences, as metabolic stress affects all body systems in different ways. For example, the immune system is inhibited, wound healing is slowed down and muscle strength is reduced.

Symptoms of a glutamine deficiency:

• Increased infectious diseases and inflammations
• Weight loss
• Muscle atrophy
• Reduced performance
• States of exhaustion
• Inner restlessness
• Sleep disorders
• Deterioration of skin, hair and nails

4 Positive effects of L-glutamine

So what are the benefits of taking glutamine? Numerous clinical studies and investigations have shown that supplementation with L-glutamine can have a positive effect on various organs and systems in the body.

1. Glutamine for a healthy gut

L-glutamine is generally beneficial to health as it supports intestinal function and digestive processes. Dietary supplements with L-glutamine can have a supportive effect on various complaints affecting the digestive system:

• For irritable bowel syndrome (IBS)
• For ulcerative colitis
• For diverticulosis
• For diverticulitis
• For leaky gut syndrome and other associated complaints such as joint pain, rosacea or autoimmune reactions

Various studies have shown that L-glutamine can reduce inflammation in the gut and help people recover from food intolerances.

The amino acid also plays an important role in maintaining healthy intestinal flora. Glutamine helps to reduce bacterial colonization of the intestine with pathogens and can thus reduce the risk of constipation or weight gain, for example.

Leaky gut syndrome is one of the main causes of autoimmune diseases. Leaky gut means something like "leaky gut". It is a disease in which harmful substances and pathogens can enter the bloodstream through the permeable intestinal membrane of the small intestine. This can lead to the development of autoimmune diseases such as Hashimoto's thyroiditis. A leaky gut also increases the risk of psoriasis, arthritis and other health problems. Treating leaky gut and maintaining gut health is supported by L-glutamine. A clinical study of 20 patients who had just had abdominal surgery shows that it also reduces inflammatory reactions such as those following surgery. Ten patients were given 30 grams of glutamine daily for a week, while the others were given a placebo drug. In the placebo group, serum glutamine levels fell and tests for leaky gut syndrome were positive. The group taking glutamine recovered much faster from the procedure. In addition, their heart values were better and their inflammation values lower.

Furthermore, glutamine contributes to the improvement of irritable bowel syndrome by balancing mucosal production. This can lead to improved bowel movements. Regular diarrhea or ulcers can be remedied with L-glutamine.

Positive effects can also be achieved with an additional intake of glutamine in the case of Hashimoto's thyroiditis or hypothyroidism.

2. The effect of L-glutamine on the psyche and brain health

L-glutamine has a significant impact on the psyche and brain health. As a precursor to the neurotransmitter glutamate, an important flavor enhancer in the culinary arts, especially in Asian dishes, glutamine is involved in many critical neurological processes. Although glutamate has a controversial reputation due to health concerns, it is essential for signal transmission between nerve cells, plays a crucial role in memory functions and is important for muscle building, appetite and sensory perception.

An outstanding property of L-glutamine is its ability to support brain function and potentially delay brain ageing. This effect can be attributed to the fact that L-glutamine promotes the health of neurotransmitters and thus ensures optimal communication within the brain.

➤ Glutamine can delay the ageing of the brain.

However, disturbances in the glutamate-glutamine cycle can lead to serious health problems, such as:

• Reye syndrome
• Epilepsy
• Bipolar disorders
• Depression
• Alcohol dependence
• States of anxiety

L-glutamine's ability to support this cycle makes it a valuable nutrient for maintaining mental health. A balanced diet and, where appropriate, targeted supplementation with L-glutamine can be important for cognitive function and mental health.

3. Glutamine for muscle building

Do you want to increase your athletic performance, boost your metabolism, improve your regeneration or build muscle? L-glutamine can help you do this. During intensive training sessions, the body is stressed and the muscles and tendons need more glutamine than is supplied by the normal diet.

After intensive training, glutamine levels can drop by 50 %. This muscle-weakening condition causes the body to use muscles for energy instead of utilizing carbohydrates. Glutamine can prevent this. Taking L-glutamine allows the muscles to perform even better, thus increasing strength and repairing the skeletal muscles.

A study has shown that taking glutamine helps muscles recover faster from intensive strength training as it improves muscle hydration. This promotes the muscle recovery process and shortens the healing time for wounds and burns.

For this reason, the intake of glutamine is not only common among bodybuilders, but is nowadays useful in almost all sports.

4. Glutamine supports the metabolism and helps with weight loss

Studies have shown that the level of human growth hormone (HGH) increases by almost 400 percent after supplementation with glutamine. This hormonal response leads to an increase in metabolism and improves the afterburn effect or EPOC after training.

This afterburning effect is crucial for burning fat, losing weight and building lean muscle mass.

So is glutamine helpful for weight loss? The amino acid helps burn fat and build lean muscle mass by lowering insulin levels and stabilizing blood sugar levels. This allows the body to use less muscle mass to maintain blood sugar and insulin sensitivity in the cells.

In a study, a six-week supplementation with 30 grams of glutamine powder per day significantly improved some cardiovascular risk factors as well as the physique of patients with type 2 diabetes. For this reason, L-glutamine is not only beneficial for diabetics, but also for people who suffer from sugar and carbohydrate cravings.

New evidence suggests that L-glutamine plays a fundamental role in cardiovascular health, as it serves as a substrate for the synthesis of DNA, ATP, proteins and lipids. In addition, it appears to have strong antioxidant and anti-inflammatory effects that can reduce the risk factors for cardiovascular diseases, for example:

• High blood pressure
• Elevated blood lipid levels
• Glucose intolerance
• Obesity
• Diabetes

In a study, 33 overweight and obese adults aged between 23 and 59 with a body mass index between 25 and 47 took either 30 grams of L-alanine or 30 grams of L-glutamine for 14 days. After these 14 days, the biomarker for obesity decreased from 0.85 to 0.57 in the L-glutamine group, while it increased in the L-alanine group. It was found that glutamine has a significant effect on weight reduction.

How does L-glutamine work in the gut?

Glutamine is the most abundant free amino acid in the human body, and the cells of the intestine use it as a major source of fuel. In the gut it does four things: it promotes the growth of new intestinal cells, it regulates the tight junction proteins that seal the gaps between these cells, it suppresses pro-inflammatory signaling pathways and it protects the cells against stress. During severe metabolic stress such as trauma, sepsis or inflammatory bowel diseases, the body's glutamine stores are depleted (Kim & Kim, 2017).

The gut barrier also comes under pressure during hard exercise in the heat. In a study with ten recreationally active men, a single dose of glutamine taken two hours before a 60-minute run at 30 °C lowered a marker of intestinal permeability compared with placebo. This was already the case at the lowest dose of 0.25 g per kg of fat-free mass, and the highest dose of 0.9 g per kg showed the clearest effect (Pugh et al., 2017).

L-glutamine also changes the composition of the gut bacteria. In the study with 33 overweight and obese adults described above, the biomarker was the ratio between two large groups of gut bacteria, Firmicutes and Bacteroidetes. After 14 days of L-glutamine, the gut flora had shifted in a way that resembles the changes seen in weight loss programs (de Souza et al., 2015).

L-glutamine for irritable bowel syndrome: what clinical trials show

Two randomized, double-blind, placebo-controlled trials have tested L-glutamine in adults with irritable bowel syndrome (IBS).

In the first trial, adults who had developed diarrhea-predominant IBS with increased intestinal permeability after a gut infection took 5 g of glutamine three times a day or a placebo for 8 weeks. 106 people completed the study. A clear improvement, defined as a drop of at least 50 points on the IBS severity score, was reached by 79.6% of the glutamine group and 5.8% of the placebo group. With glutamine, the number of daily bowel movements was 2.9, compared with 5.4 with placebo, the stools became firmer and the intestinal permeability returned to normal. Side effects were rare and no more common than with placebo (Zhou et al., 2019).

In the second trial, 50 adults with IBS followed a low FODMAP diet and took either 15 g of glutamine a day or a placebo for 6 weeks. In the glutamine group, the IBS severity score fell by 58%. An improvement of more than 45% was seen in 88% of the participants who took glutamine, compared with 60% of those who followed the diet with a placebo. No serious side effects occurred (Rastgoo et al., 2021).

Herbano offers the amino acid as a pure L-glutamine powder from plant fermentation, vegan and free from additives.

When should you take glutamine?

There are two forms of L-glutamine. Regular L-glutamine is available in the so-called free form, which should ideally be taken with food so that it can be properly absorbed by the body.

The other form is known as alanyl-L-glutamine. This is an amino acid that is bound to another amino acid. This basically means that it can be digested much better.

Both forms are best taken immediately after or before training - with a small meal immediately before or after training to support metabolism and weight loss as well as muscle building, recovery and maintenance.

It can take up to five days to replenish glutamine levels after an intense workout, so it is important to take it regularly if you are training intensively.

Some bodybuilders believe that glutamine works best in combination with certain BCAAs (Branched Chain Amino Acids), especially leucine. Others take it after training together with creatine to improve muscle recovery and replenish the body's energy stores.

How much L-glutamine for the gut, and how long until it works?

The clinical studies on the gut used the following amounts and periods:

How quickly L-glutamine works therefore depends on the goal. A single dose before exercise was enough to protect the gut barrier during a run in the heat. After abdominal surgery, intestinal permeability had fallen after one week (Quan et al., 2004). In irritable bowel syndrome, the improvements were measured after six to eight weeks of daily intake.

For healthy adults, a risk assessment of the published human studies found strong evidence for the absence of adverse effects at supplemental intakes of up to 14 g of L-glutamine a day. Much higher amounts have also been tested without adverse effects (Shao & Hathcock, 2008).

With the Herbano L-glutamine powder, one measuring spoon holds approx. 3 g. It is dissolved in a glass of water and taken with a meal.

Side effects of glutamine

All in all, glutamine is safe in moderate amounts and for short-term use. There is only a low risk of side effects with a dose of up to 30 grams per day.

Although the effects of excess glutamine rarely cause problems, it is advisable to take additional B vitamins with long-term oral glutamine intake. This applies in particular to vitamin B12, which controls the build-up of glutamine in the body.

Who should not take glutamine?

People with kidney or liver disease, Reye's syndrome or cancer should only take this food supplement in consultation with a doctor, as these conditions can impair the absorption of amino acids.

Chronic intake of glutamine could have an effect on tumor growth and may therefore increase the risk of cancer.

In rare cases, allergic reactions to this food supplement have been reported. Discontinue use immediately if you experience symptoms such as nausea, vomiting, hives, dizziness or pain.

Frequently asked questions

Does L-Glutamine really heal the gut?

L-glutamine is a major fuel for the cells of the intestinal lining and regulates the tight junctions that seal the gut barrier. In a randomized trial in people with irritable bowel syndrome after a gut infection, the raised intestinal permeability returned to normal after 8 weeks with 5 g three times a day. After abdominal surgery, 30 g a day lowered intestinal permeability within one week.

How long does it take L-Glutamine to heal the gut?

That depends on the situation. After abdominal surgery, intestinal permeability had fallen after 7 days of glutamine, and in irritable bowel syndrome the improvements were measured after 6 to 8 weeks of daily intake. A single dose two hours before exercise already protected the gut barrier during a run in the heat.

What happens when you take L-Glutamine every day?

In the trials on irritable bowel syndrome, daily glutamine over 6 to 8 weeks reduced the severity of the symptoms, and in the 8-week trial bowel movements became less frequent and stools firmer. For healthy adults, intakes of up to 14 g a day are well documented as free of adverse effects. With long-term intake, it is advisable to take additional B vitamins, in particular vitamin B12.

When to take L-glutamine for gut health?

Regular L-glutamine in the free form should ideally be taken with food so that the body can absorb it properly. In the trial on irritable bowel syndrome, the daily amount was split into three portions of 5 g. For sport, it is best taken immediately before or after training with a small meal.

Can L-glutamine reduce IBS symptoms like bloating or diarrhea?

In people with diarrhea-predominant IBS after a gut infection, glutamine lowered the number of daily bowel movements to 2.9, compared with 5.4 with placebo, and made the stools firmer. In a second trial, 15 g of glutamine a day on top of a low FODMAP diet lowered the IBS severity score, which also takes abdominal pain and bloating into account, by 58%.

Sources (in English):

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Zhou, Q., Verne, M. L., Fields, J. Z., Lefante, J. J., Basra, S., Salameh, H., & Verne, G. N. (2019). Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome. Gut, 68(6), 996–1002. doi:10.1136/gutjnl-2017-315136

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