Lactobacillus species are widely studied probiotics with a body of evidence supporting their use in the management of colitis, particularly ulcerative colitis and, to a lesser extent, Crohn’s disease. The rationale for their use is based on their ability to restore the balance of the gut microbiota, enhance mucosal barrier function, and modulate immune responses. Several clinical trials and meta-analyses have investigated their efficacy. For example, a 2020 systematic review in Alimentary Pharmacology & Therapeutics found that certain probiotic formulations containing Lactobacillus (often combined with Bifidobacterium and other strains) were associated with higher rates of remission and lower relapse rates in ulcerative colitis compared to placebo, though the effect size was modest and varied by formulation and patient population. The evidence for Crohn’s disease is weaker, with most trials showing little to no benefit. Mechanistically, in vitro and animal studies have shown that Lactobacillus can reduce inflammation, enhance production of anti-inflammatory cytokines, and compete with pathogenic bacteria. However, results are mixed, and not all Lactobacillus strains are equally effective; some strains have no effect. Overall, while there is scientific validation for the use of certain Lactobacillus strains in colitis, especially in mild to moderate ulcerative colitis, the evidence is not uniformly strong or conclusive, warranting a moderate rating.