The protective effects of glutamine on radiation-induced diarrhea

Glutamine is a neutral amino acid that is used by rapidly dividing cells such as erythrocytes, lymphocytes, and fibroblasts. It is also the substrate of glutathione synthesis. In normal metabolic rates, glutamine is an amino acid synthesized endogenously, but in high metabolic conditions such as cancer, it must be taken exogenously. Animal studies strongly demonstrate that glutamine protects both the upper and lower gastrointestinal tract mucosa from the effects of chemotherapy, radiotherapy, or other causes of injury. In this study, we investigated the protective effect of glutamine on radiation-induced diarrhea.

The patients were divided into glutamine-treated and placebo groups. In the glutamine-treated group, 15 g of oral glutamine was administered three times daily. The patients were evaluated for diarrhea grade according to the National Cancer Institute Common Toxicity Criteria version 3.0, (Table 1), need for loperamide use, need for supportive parenteral therapy, and treatment breaks due to diarrhea.

There was no difference in overall diarrhea incidence when the two groups were compared. When diarrhea grade was evaluated, none of the patients in the glutamine-treated group had grade 3-4 diarrhea, but in the placebo group, grade 3-4 diarrhea was seen in 69 % of the patients. In the placebo-treated group, patients requiring loperamide and parenteral supportive therapy were 39 and 92 %, respectively. There was no treatment break in glutamine-treated patients.

Glutamine may have protective effect on radiation-induced severe diarrhea.