Glutamine as a therapeutic supplement
Glutamine, also known as L-glutamine, is a conditionally essential amino acid that plays a vital role in various bodily functions, including immune system health and digestive tract support. It serves as a primary fuel source for the cells lining the intestines and can be depleted during periods of intense physical stress, such as heavy exercise, surgery, or illness. As a therapeutic supplement, glutamine is primarily proposed for use in managing conditions like sickle cell disease, where it is FDA-approved to reduce complications.
Moreover, glutamine has been explored for its potential benefits in a variety of other health issues, including angina, attention deficit disorder, Crohn’s disease, and irritable bowel syndrome. Preliminary studies suggest it may help prevent post-exercise infections in athletes and support recovery in critically ill patients. However, research findings are mixed, especially regarding its effectiveness for digestive disorders and sports performance enhancement.
Generally considered safe when taken within recommended dosages, glutamine may pose risks for certain individuals, particularly those with specific medical conditions or on certain medications. As interest in glutamine as a supplement grows, further research is necessary to confirm its benefits and optimize its use in various therapeutic contexts.
Glutamine as a therapeutic supplement
- DEFINITION: Natural substance of the human body used as a supplement to treat specific health conditions.
- PRINCIPAL PROPOSED USES: Sickle Cell Disease
- OTHER PROPOSED USES: Angina, attention deficit disorder, Crohn’s disease, enhancing mental function, food allergies, human immunodeficiency virus infection support, irritable bowel syndrome, overtraining syndrome, post-exercise colds, ulcerative colitis, ulcers, undesired weight loss
Overview
Glutamine, or L-glutamine, is an amino acid derived from another amino acid, glutamic acid. Glutamine plays a role in the health of the immune system, digestive tract, muscle cells, and other bodily functions. It serves as fuel for the cells that line the intestines. Heavy exercise, infection, surgery, and trauma can deplete the body’s glutamine reserves, particularly in muscle cells.
The fact that glutamine does so many good things in the body has led people to try glutamine supplements as a treatment for various conditions, including preventing the infections that often follow endurance exercise, reducing symptoms of overtraining syndrome, improving nutrition in critical illness, alleviating allergies, and treating digestive problems.
Requirements and Sources
There is no daily requirement for glutamine because the body can make its supply. Various severe stresses may result in a temporary glutamine deficiency. High-protein foods, such as meat, fish, beans, and dairy products, are excellent sources of glutamine. Typical daily food intake ranges from approximately 1 to 6 grams (g).
Therapeutic Dosages
Typical therapeutic dosages of glutamine used in studies ranged from 3 to 30 g daily, divided into several doses.
Therapeutic Uses
Endurance athletes frequently catch a cold after completing a marathon or similar forms of exercise. Preliminary evidence, including one small double-blind, placebo-controlled trial, suggests that glutamine supplements might help prevent such infections.
Another small double-blind, placebo-controlled trial suggests that glutamine might support standard therapy for angina. Angina is too dangerous a disease for self-treatment. A person with angina should not take glutamine (or any other supplement) except on the advice of a physician.
Because, as noted above, cells of the intestine use glutamine for fuel, the supplement has been tried as a supportive treatment for various digestive conditions with mixed results. Tested uses include reducing diarrhea caused by the drug nelfinavir (used to treat human immunodeficiency virus, or HIV), digestive distress caused by cancer chemotherapy, and symptoms of inflammatory bowel disease.
Glutamine appears to help reduce leakage through the intestinal wall. On this basis, glutamine has also been suggested as a treatment for food allergies, according to the idea that in some people, whole proteins leak through the wall of the digestive tract and enter the blood, causing allergic reactions (so-called leaky gut syndrome). However, there is little reliable evidence that glutamine provides any benefits for food allergies.
Preliminary evidence suggests that glutamine combined with antioxidants or other nutrients may help people with HIV to gain weight. Glutamine (often combined with other nutrients) also appears to be useful as a nutritional supplement for people undergoing recovery from major surgery or critical illness.
Glutamine has been tried as an ergogenic aid for bodybuilders, but two small trials failed to find any evidence of benefit. Based on glutamine’s role in muscle, it has been suggested that glutamine might be useful for athletes experiencing overtraining syndrome. As the name suggests, this syndrome is the cumulative effect of a training regimen that allows too little rest and recovery between workouts. Symptoms include depression, fatigue, reduced performance, and physiological signs of stress. Glutamine supplements have been proposed as a treatment for attention deficit disorder and ulcers and as a “brain booster.” However, further research is required.
Glutamine is approved by the United States Food and Drug Adminstration (FDA) as a prescription medication (Endari) to reduce the frequency of complications due to sickle cell anemia. It prevents damage to red blood cells.
Scientific Evidence
Infections in athletes. Endurance exercise temporarily reduces immunity to infection. This effect may be partly due to the reduction of glutamine in the body, although not all studies agree.
A double-blind, placebo-controlled study evaluated the benefits of supplemental glutamine (5 g) taken at the end of exercise in 151 endurance athletes. The results showed a significant decrease in infections among treated athletes. Only 19 percent of the athletes taking glutamine got sick, compared with 51 percent of those on a placebo.
Recovery from critical illness. One small double-blind study found that glutamine supplements might have significant nutritional benefits for seriously ill people. In this study, eighty-four critically ill hospital patients were divided into two groups. All the patients were being fed through a feeding tube. One group received a regular feeding-tube diet, whereas the other group received this diet plus supplemental glutamine. After six months, fourteen of the forty-two patients receiving glutamine had died, compared with twenty-four of the control group. The glutamine group also left both the intensive care ward and the hospital significantly sooner than the patients who did not receive glutamine. Benefits have been seen in other controlled trials as well.
HIV support. One double-blind, placebo-controlled study of twenty-five people found that using glutamine at 30 g daily for seven days reduced diarrhea caused by the protease inhibitor nelfinavir. In addition, combination supplements containing glutamine may help reverse HIV-related weight loss. For example, a double-blind, placebo-controlled study found that a combination of glutamine and antioxidants (vitamins C and E, beta-carotene, selenium, and N-acetyl cysteine) led to significant weight gain in people with HIV who had lost weight. Another small double-blind trial found that combination treatment with glutamine, arginine, and beta-hydroxy beta-methylbutyrate (HMB) could increase muscle mass and possibly improve immune status.
Cancer chemotherapy. There is mixed evidence regarding whether glutamine can reduce the side effects of cancer chemotherapy. A double-blind, placebo-controlled trial of seventy people undergoing chemotherapy with the drug 5-FU for colorectal cancer found that glutamine at a dose of 18 g daily improved intestinal function and structure and reduced the need for antidiarrheal drugs. However, a double-blind trial of sixty-five women undergoing various forms of chemotherapy for advanced breast cancer failed to find glutamine at 30 g per day helpful for reducing diarrhea. Based on a review of several studies, there is some preliminary evidence that glutamine may help relieve the pain associated with nerve damage (peripheral neuropathy) caused by some chemotherapy drugs. Further research found glutamine was able to ameliorate oral mucositis following chemotherapy using a topical and oral supplement.
Angina. Researchers conducted investigations in rats and found that glutamine could protect the heart from damage caused by loss of oxygen. Based on these findings, they went on to evaluate the effects of glutamine in ten people with chronic angina who were also taking standard medication. In this double-blind, placebo-controlled trial, each participant received a single oral dose of glutamine (80 mg per kg of body weight) or a placebo forty minutes before a treadmill test. A week later, each participant received the opposite treatment. The results showed that the use of glutamine significantly enhanced the ability of participants to exercise without showing signs of heart stress. Based on animal studies, researchers suggested a higher dose of glutamine would be worth trying. Further study found positive results. Glutamine may lower one's risk of developing heart disease.
Crohn’s disease. Because glutamine is the primary fuel source for cells of the small intestine, glutamine has been proposed as a treatment for Crohn’s disease, a disease of the small intestine. However, two double-blind trials enrolling thirty people found no benefit.
Sports performance. A double-blind, placebo-controlled trial of thirty-one people ranging from eighteen to twenty-four years of age evaluated the potential benefits of glutamine as a sports supplement for improving response to resistance training (weightlifting). Participants received either a placebo or glutamine at a dose of 0.9 g per kg of lean tissue mass. After six weeks of resistance training, participants taking glutamine showed no relative improvement in performance, composition, or muscle protein degradation. Similarly, negative results were seen in a small double-blind, placebo-controlled trial of weightlifters using a dose of 0.3 g per kg of total body weight.
Safety Issues
As a naturally occurring amino acid, glutamine is thought to be a safe supplement when taken at recommended dosages. There is strong evidence that glutamine is safe at levels up to 14 g per day, although higher dosages have been tested without apparent adverse effects.
Nevertheless, those who are hypersensitive to monosodium glutamate (MSG) should use glutamine with caution, as the body metabolizes glutamine into glutamate. Additionally, because many antiepilepsy drugs work by blocking glutamate stimulation in the brain, high dosages of glutamine might conceivably overwhelm these drugs and pose a risk to people with epilepsy. In one case report, high doses of the supplement L-glutamine (more than 2 g per day) may have triggered episodes of mania in two people not previously known to have bipolar disorder. In a small, randomized trial including thirty older people, L-glutamine did not cause any clinically significant changes in lab tests. The researchers urged caution, though, since there were some statistically significant changes for certain kidney levels. Maximum safe dosages for young children, pregnant or nursing women, and those with severe liver or kidney disease have not been determined.
Important Interactions
Individuals taking antiseizure medications—carbamazepine, phenobarbital, phenytoin (Dilantin), primidone (Mysoline), and valproic acid (Depakene)—should use glutamine only under medical supervision. People taking nelfinavir or other protease inhibitors for HIV or cancer chemotherapy drugs should note that concurrent glutamine may reduce intestinal side effects.
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