The use of bacteria, specifically probiotics, to support or treat colitis is primarily justified by scientific evidence. Colitis, which involves inflammation of the colon, can result from various causes, including ulcerative colitis and infectious colitis. Probiotics—live microorganisms that confer health benefits to the host—have been studied extensively for their role in modulating gut microbiota and reducing inflammation in colitis patients.

Clinical trials have shown that certain probiotic strains, such as Lactobacillus, Bifidobacterium, and the yeast Saccharomyces boulardii, may help maintain remission and reduce symptoms in patients with ulcerative colitis and, to a lesser extent, Crohn’s disease. For example, the probiotic mixture VSL#3 has demonstrated efficacy in maintaining remission in ulcerative colitis and in preventing pouchitis (a complication after surgery for ulcerative colitis). The mechanism is thought to involve restoration of the balance of intestinal microflora and modulation of immune responses in the gut.

However, the effectiveness of probiotics varies depending on the strain, formulation, and individual patient characteristics. Large meta-analyses and systematic reviews generally support a modest benefit, particularly in ulcerative colitis, though results are inconsistent, and not all probiotics are equally effective. Guidelines from gastroenterological societies sometimes recommend specific probiotic preparations as adjunct therapy. Overall, the use of bacteria in supporting/treating colitis is evidence-based but should be tailored to the patient and type of colitis.