L-Glutamine is an essential nutrient naturally present in the human body. How important is it? By the end of this introduction, you’ll understand just how crucial it is.
What is Glutamine? (Also known as L-Glutamine)
There are a total of 22 amino acids that constitute the proteins in the body. All amino acids share the common characteristic of containing an amine group (NH3+) and a carboxyl group (COO–). A classification based on whether the body synthesizes them categorizes them into `essential amino acids` or `non-essential amino acids`. Essential amino acids are those the body `cannot produce on its own` and therefore must be supplemented through `diet`, while non-essential amino acids are synthesized by the body.
L-Glutamine is an amino acid synthesized by the liver and skeletal muscles at a rate of approximately 40-80 grams per day, making it a non-essential amino acid. However, under certain physiological conditions, this amino acid may be heavily consumed or synthesized in lesser amounts, causing it to be elevated from a non-essential amino acid to an essential one. In such cases, this amino acid is termed conditionally essential amino acid.
What foods contain Glutamine?
Glutamine is found in protein-rich foods. It is estimated that approximately 3-6 grams of glutamine can be obtained from the diet each day`[1]`. Here are the glutamine contents in various foods`[2]`:
- 100 grams of beef contains 1.2 grams
- 100 grams of tofu contains 0.6 grams
- 100 grams of eggs contain 0.56 grams
- 100 grams of corn contain 0.41 grams
- 100 grams of white rice contain 0.3 grams
The 12 Functions of Glutamine
Glutamine plays a crucial role in the body, and here are 12 important `physiological functions` associated with it:
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Cellular Energy Source
Rapidly growing cells, such as those in the digestive tract epithelium and immune system, depend on glutamine to a degree even greater than glucose.
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Involved in Nitrogen Circulation in the Body
Ammonia is a major by-product of protein metabolism and is toxic to organisms. Most of the ammonia is converted to proline and glutamine and then transported to the liver and kidneys for excretion or to provide raw materials for other tissues.
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Beneficial for Muscles
The skeletal muscle is the largest reservoir of glutamine in the body. Supplementing glutamine can stimulate protein and glycogen synthesis, increase muscle strength, slow down muscle protein breakdown, and help prevent muscle atrophy`[3][4]`.
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Benefits the Immune System
Glutamine serves as an energy source for immune cells, and even in infections and high metabolic states, the rate of glutamine consumption is higher than that of glucose. Additionally, glutamine is involved in immune cell `pathogen recognition` and `tissue repair` during the immune response`[5]`.
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Cell Protection and Antioxidant Abilities
Glutamine can be metabolized into the important antioxidant `glutathione`, thus enhancing the body’s antioxidant capacity. Additionally, glutamine can regulate the expression of the stress protein – `heat shock proteins` and is involved in modulating the inflammation pathway triggered by NF-κB`[5]`.
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Maintains Blood Acid-Base Balance
Under normal physiological conditions, the human body’s blood pH needs to be maintained between 7.35-7.45. Glutamine is among the three systems that maintain blood pH levels. Its structure, with its amide and amine groups, can bind with hydrogen ions to regulate hydrogen ion concentration and maintain blood pH balance.
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Assists the Gastrointestinal Tract
Gastrointestinal cells have a significant demand for glutamine. Apart from maintaining gut mucosal integrity, reducing gastrointestinal permeability, and lowering gut inflammation, research has found that glutamine can alter the gut microbiota`[6]`.
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Synthesis of Glucosamine
Glucosamine, a common component in bone and joint health supplements, requires glutamine’s involvement in the body’s synthesis process.
Besides participating in numerous physiological metabolisms, glutamine exhibits particularly significant effects for specific groups:
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Assistance in Postoperative Recovery
Retrospective studies found that postoperative administration of 180-500 mg/kg/day of glutamine for 5-7 consecutive days could help postoperative patients maintain `positive nitrogen balance`, reduce postoperative infection rates, and shorten hospital stays`[7]`.
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Support for Cancer Patients
Cancer patients are in a state of high metabolism and consume a substantial amount of glutamine, leading to a deficiency in synthesized glutamine. Therefore, supplementing with glutamine is recommended for cancer patients, as it can help reduce the side effects of chemotherapy and radiotherapy. Adequate glutamine supplementation has been found to result in a `better recovery`. Oral and gastrointestinal mucositis are common side effects of chemotherapy and radiation therapy, which significantly affect the quality of life. Research has found that providing chemotherapy and radiation therapy patients with 3 times a day, 10 grams of glutamine can reduce the frequency, duration, and severity of oral or esophageal mucositis`[9]`.
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Gastrointestinal Diseases
One of the most common causes of gastric ulcers is Helicobacter pylori infection. Animal studies have found that supplementing with glutamine can effectively reduce gastric symptoms caused by Helicobacter pylori infection, with results `comparable to the anti-ulcer drug marzulene[10]`.
The integrity of the intestinal barrier plays a crucial role in the absorption of nutrients and resistance to foreign pathogens and toxins. When the intestinal barrier is compromised, it increases intestinal permeability, allowing large molecules and bacteria that normally cannot pass through the intestinal barrier to do so, leading to allergies and systemic inflammation symptoms. This condition is known as Leaky Gut Syndrome. Supplementing with glutamine can strengthen the small intestine barrier, reduce intestinal permeability, and accelerate the repair of the damaged small intestine[11]. -
Sports and Fitness Enthusiasts
Athletes and fitness enthusiasts often use supplements to increase muscle mass or enhance overall athletic performance. Studies have found that supplementing with 0.3 grams of glutamine per kilogram of body weight can shorten the recovery time for muscle injuries and reduce muscle soreness`[12]`. Another clinical study noted that supplementing with glutamine can reduce damage and inflammation caused by high-intensity aerobic exercise`[13].
Possible Side Effects of Excessive Glutamine Supplementation
In general, glutamine supplementation rarely results in adverse reactions. According to data from the National Institutes of Health (NIH) in the United States, there have been no reports of adverse reactions when supplementing with 45 grams of glutamine per day for six weeks. Additionally, critically ill patients receiving 0.42 grams of glutamine per kilogram of body weight did not experience adverse reactions[14].
However, considering individual dietary habits and variations in the amount of glutamine obtained from food, the average intake of glutamine ranges from 3-6 grams. Therefore, when supplementing, it is advisable to start with a lower dose of 5 grams per day and gradually increase it to 14 grams per day. This is currently considered a safe long-term supplementation dose[15]. The only group that needs special attention is individuals with impaired liver or kidney function, who should closely monitor their liver and kidney function indices when supplementing with glutamine.
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