Glutamine 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, and muscle cells, as well as other bodily functions. It appears to serve as a 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.

There is no daily requirement for glutamine because the body can make its own supply. As mentioned earlier, 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 intake from food ranges from approximately 1 to 6 g.

Typical therapeutic dosages of glutamine used in studies ranges from 3 to 30 g daily, divided into several separate doses.

Infections in Athletes

Endurance exercise temporarily reduces immunity to infection. This effect may be due in part to reduction of glutamine in the body, although not all studies agree. ¹ A double-blind, placebo-controlled study evaluated the benefits of supplemental glutamine (5 g) taken at the end of exercise in 151 endurance athletes. ² The results showed a significant decrease in infections among treated athletes. Only 19% of the athletes taking glutamine got sick, as compared to 51% of those on placebo.

For other approaches to this problem, see the article titled Sports and Fitness Support: Aids to Recovery .

Recovery From Critical Illness

One small double-blind study found that glutamine supplements might have significant nutritional benefits for seriously ill people. ³ In this study, 84 critically ill hospital patients were divided into two groups. All the patients were being fed through a feeding tube. One group received a normal feeding-tube diet, whereas the other group received this diet plus supplemental glutamine. After 6 months, 14 of the 42 patients receiving glutamine had died, compared with 24 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. ⁴

HIV Support

One double-blind, placebo-controlled study of 25 people found that use of glutamine at 30 g daily for 7 days reduced diarrhea caused by the protease inhibitor nelfinavir. ⁵ 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. ⁶ 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. ⁷

Cancer Chemotherapy

There is mixed evidence regarding whether glutamine can reduce the side effects of cancer chemotherapy . A double-blind, placebo-controlled trial of 70 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. ⁸ However, a double-blind trial of 65 women undergoing various forms of chemotherapy for advanced breast cancer failed to find glutamine at 30 g per day helpful for reducing diarrhea. ⁹ 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. ¹⁰

Angina

Researchers conducted investigations in rats and found that glutamine could protect the heart from damage caused by loss of oxygen. ¹¹ 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 placebo 40 minutes before a treadmill test. A week later, each participant received the opposite treatment. The results showed that use of glutamine significantly enhanced the ability of participants to exercise without showing signs of heart stress. Based on the results in rats, researchers suggest that a higher dose of glutamine would be worth trying.

Crohn's Disease

Because glutamine is the major 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. ¹² However, two double-blind trials enrolling a total of 30 people found no benefit. ¹³

Sports Performance

A double-blind, placebo-controlled trial of 31 people ranging from 18 to 24 years of age evaluated the potential benefits of glutamine as a sports supplement for improving response to resistance training (weight lifting). ¹⁴ Participants received either placebo or glutamine at a dose of 0.9 g per kg of lean tissue mass. After 6 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. ¹⁵

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