Small intestinal bacterial overgrowth (SIBO) refers to a condition in which abnormally large numbers of bacteria are present in the small intestine. Gastrointestinal cancer is related to compromised intestinal barrier function, reduced functionality of immune responses, and inadequate nutritional status, which impair the ability of patients to control intestinal bacterial proliferation. These result in conditions favourable to SIBO. However, the actual incidence of SIBO in patients with gastrointestinal cancer and its relation to clinical symptoms has not been explored.


A recent case-control study, led by Dr. Zhenjun Wu from the Department of Blood Transfusion and Clinical Laboratory at Qingdao University School of Medicine in Qingdao (China), has found that probiotics may combat SIBO in patients with gastrointestinal cancer and may alleviate some gastrointestinal symptoms.


The researchers evaluated 112 gastric and 88 colorectal cancer patients (aged 25-75 years). The control group consisted of 80 healthy volunteers (aged 20-65 years). Questionnaires were used to assess gastrointestinal symptoms and a glucose hydrogen breath test was used to determine SIBO status.


63.0% of patients with gastric and colorectal cancer versus 16.3% of controls tested positive for SIBO, which suggests that gastrointestinal cancer may be associated with SIBO. Besides this, proton pump inhibitor use in patients with gastrointestinal malignancies made SIBO more likely to occur.


In SIBO-positive cancer patients, probiotic (Bifidobacterium triple viable capsule) therapy for 4 weeks counteracted SIBO. After the intervention, the group receiving the probiotic treatment had 19.0% SIBO-positive patients, whereas the group that was administered placebo showed 74.6% SIBO-positive patients. Noticeably, counteracting SIBO with the Bifidobacterium triple viable capsule probiotic reduced gastrointestinal symptoms in patients with gastrointestinal malignancies.


In conclusion, SIBO’s prevalence is higher in patients with gastrointestinal cancer and a probiotic intervention for 4 weeks may combat SIBO in these patients, in addition to alleviating some of their gastrointestinal symptoms. Gastrointestinal symptoms in patients with gastrointestinal malignancies may possibly partially be because of SIBO and fits well with the processes likely to occur not only in such patients, but also in other intestinal oncological diseases.





Liang S, Xu L, Zhang D, Wu Z. Effect of probiotics on small intestinal bacterial overgrowth in patients with gastric and colorectal cancer. Turk J Gastroenterol. 2016; 27(3):227-32. doi: 10.5152/tjg.2016.15375.

Lin HC. Small intestinal bacterial overgrowth: a framework for understanding irritable bowel syndrome. JAMA. 2004; 292(7):852-8. doi: 10.1001/jama.292.7.852.