Diarrhea is a common side-effect of pelvic and abdominal radiation therapy. In a fascinating study, published in 2010, researchers reported that taking a probiotic supplement before and during radiation therapy for cervical cancer significantly reduced the incidence of moderate (grade 2) and severe diarrhea (grade 3) compared with patients who received a placebo; grade 2 and 3 diarrhea (45% in the placebo group versus 9% in the probiotic group). These beneficial results were supported by the reduction in the use of anti-diarrheal medications among the patients taking the probiotic supplement (9% used anti-diarrheals) versus the placebo (32% used anti-diarrheals).
The probiotic regimen: 2 × 109 units of a lactobacillus acidophilus plus bifidobacterium bifidum (equivalent to 2 capsules) two times a day before meals (morning and evening), beginning 7 days before starting radiotherapy and continuing everyday during radiotherapy.
*This was a relatively small randomized controlled trial (RCT), so the results can not be generalized. Although this study is compelling, the results should be confirmed by more robust studies with greater numbers of patients.*
What are probiotics?
Probiotics are live microorganisms (in most cases, bacteria) that are similar to beneficial microorganisms found in the human gut (such as the two employed in the above study). They are also called “friendly bacteria” or “good bacteria.” Data suggest that there may be enhanced synergistic effects when multiple probiotics are combined.
How might probiotics work in reducing radiation-induced diarrhea?
Radiation therapy (and chemotherapy) can cause a temporary inflammatory response within the affected bowel. If the degree of inflammation is significant, it can lead to reduced absorption of nutrients and water and impair the growth of normal ‘healthy’ intestinal bacteria that colonize the bowel (aiding in digestion, regulating bowel elimination, and possibly enhancing immune function) Reduction in the amount of normal bowel bacteria can lead to an opportunistic increase in growth of competing ‘unhealthy’ microorganisms, leading to further impaired digestion. The science on the physiology, mechanisms of action and efficacy of probiotics remains an area of controversy.
As probiotics are “live” microorganisms, use of these supplements should be first discussed with your physicians if you are immunocompromised. There have been rare reports of bacterial infections in the blood (septicemia) of individuals who used probiotics. Probiotics are not regulated by the Food and Drug Administration as they are considered food or supplements. Product quality, consistency and composition are not all the same among the different brands and batches. It is important to only purchase supplements from the most reputable manufacturers.
Learn more about probiotics on the National Center for Complementary and Alternative Medicine (NCCAM) website
Nice article on probiotic foods from the Los Angeles Times