Glutamine is a nonessential amino acid, meaning that the body is able to synthesize it on its own and is also contained in most dietary proteins. Glutamine plays an important role in many body functions and serves as:
Fuel source for small bowel enterocytes
Nitrogen donor for certain synthetic pathways
Precursor to both nucleic acid and nucleotide synthesis
Regulator of acid- base balance
Cellular energy source of the immune system for lymphocytes, macrophages and fibroblasts
Glutamine depletes during catabolism in conditions that cause metabolic stress, including trauma and infection. Under these conditions, intracellular glutamine levels may be reduced by 50% or more. Cancer patients have glutamine depletion because tumors use this amino acid, leading to protein catabolism.
Exhaustion of skeletal muscle glutamine due to tumor growth leads to cachexia. The scientific community believes that tumor exacerbates the loss of glutamine in cancer patients and that glutamine has the potential to delay or stop tumor growth due to its immunomodulatory effect.
The results from animal and human research on the use of glutamine in cancer are contradictory. Researchers are concerned that glutamine supplementation leads to an increase in tumor growth in cancer patients following in vitro studies revealing an increase in cell growth by glutamine supplementation. Subsequent in vivo studies showed the opposite effect, which is a decrease in tumor growth.
Research has shown that glutamine intake in colon cancer patients, regardless of tumor size and cell type, is comparable to uptake in healthy intestinal tissue patients, reassuring the research community of whether glutamine is absorbed more quickly into bowel diseases.
In early studies in rats, it was found that the glutamine-enhanced diet resulted in a 60% increase in muscle glutamine without increasing the volume or use of glutamine. Also, supplemental administration of glutamine to rats receiving methotrexate chemotherapy was found to increase tumor methotrexate concentration, reduce methotrexate-induced side effects and improve survival.
Most studies of supplemental glutamine in patients receiving chemotherapy have focused on assessing its role in relieving side effects. In a randomized, double-blind study of oral administration of glutamine (16 g/day) or placebo in 18 patients receiving chemotherapy for gastrointestinal cancer it appeared that glutamine was well tolerated but had no significant effect on the oral mucosa as estimated by patients and researchers. Other studies have found some benefits of glutamine. A randomized, double-blind, crossover study of 24 patients receiving chemotherapy that causes mucositis, patients received glutamine or placebo or placebo followed by glutamine. The results showed that the severity and duration of the pain in the mouth was significantly less when supplementing with glutamine plus chemotherapy.
The effect of glutamine on chemotherapy-induced diarrhea has also been explored. Oral glutamine (18g / day for 15 days) was administered to half of the 70 colon cancer patients before chemotherapy and the remaining half of the patients received a placebo. The duration of diarrhea was 1.9 days in the glutamine group, compared with 4.5 days for the placebo group. Patients taking glutamine also received less tablets of loperamide to manage diarrhea. In another study, patients who received glutamine had a significant reduction in numbness of the fingers and legs.
The results of the evaluation of the research on the potential benefits of glutamine in the treatment of cancer are encouraging but remain unclear. Some researchers have recently suggested that glutamine may in fact be an essential amino acid. Reductions in glutamine levels after trauma or major burns, postoperatively, and in patients with diseases such as inflammatory bowel diseases, AIDS and cancer have been quoted. Further research to confirm the mechanism of action and efficacy of glutamine as adjuvant therapy in patients treated with cancer is essential.
Decker GM. Glutamine: indicated in cancer care? Clin J Oncol Nurs. 2002;6(2):112-115.
: L-Glutamine & Chios Mastiha