Probiotics may help reduce the severity of one of the most common acute adverse effects of radiation—diarrhea. They just might not show results right away. According to a study by researchers from the Centre Hospitalier Universitaire de Québec in Canada, the effects of probiotics were positive and most effective in the weeks after radiation treatment.
No prophylactic agents are approved for preventing pelvic radiation enteritis, the researchers note, and evidence is weak for nutritional interventions that have been tried. But recently, more research is pointing to a powerful role for probiotics in a variety of gastrointestinal uses.
This study compared the efficacy of the probiotic Bifilact (Lactobacillus acidophilus LAC-361 and Bifidobacterium longum BB-536) with placebo. The main goal was to find whether probiotics would prevent or delay the incidence of moderate-to-severe radiation-induced diarrhea during a radiotherapy treatment. Secondary goals were to assess whether Bifilact reduced or delayed the need of antidiarrheal medication, reduced intestinal pain, reduced the need for hospitalization, minimized interruptions to radiotherapy treatments, and improved patient well-being.
In the study, 229 patients received either placebo or 1 of 2 Bifilact regimens: a standard dose twice a day or a high dose 3 times a day. Patients recorded their digestive symptoms every day and met with a registered dietitian and radiation oncologist every week during treatment.
Although the differences were not statistically significant, probiotics eventually halved the proportion of patients with moderate-to-severe diarrhea. The mean number of bowel movements per 24 hours was 2.3 in the placebo group, 2.3 in the standard-dose, and 2.1 in the high-dose patients (P = .84). During the treatment, those numbers changed to 2.9, 2.7, and 2.8 bowel movements per day (P = .80), respectively. For patients who underwent surgical procedures before radiation, probiotic intake tended to reduce all levels of diarrhea, especially the most severe grade 4 diarrhea. Median abdominal pain was initially 0 for all groups and < 1 during treatment for all groups (P = .23).
To their knowledge, the researchers say, only 6 human clinical studies have been published regarding using probiotics to prevent acute radiation-induced diarrhea, and only 1 for treating diarrhea after radiotherapy. The 6 studies showed positive results on diarrhea toxicity and/or frequency of bowel movement and/or stool consistency. Two of 3 systematic reviews also found a probable beneficial effect on prevention.
Their own study produced some interesting findings, the researchers say. For one, less diarrhea at 60 days meant the benefit began at the end of the treatment or after it. Patients with a standard dose of probiotic experienced less of the moderate-to-severe diarrhea at the end of treatment or during the 2 weeks following treatment. And after 60 days, 35% of patients in the standard-dose group did not have moderate-to-severe diarrhea, compared with 17% in the placebo group (P = .23). The researchers say the probiotic effect may be delayed because of the time required by bacteria to exert their influence on the inflammatory process.
Demers M, Dagnault A, Desjardins J. Clin Nutr. 2014;33(5):761-767.