Lactobacillus paracasei has been investigated as a probiotic for supporting or treating colitis, particularly in preclinical studies and several small human trials. The rationale for its use is based on the understanding that colitis, including ulcerative colitis and other forms of inflammatory bowel disease (IBD), is associated with dysbiosis (an imbalance in gut microbiota) and inflammation of the colon. L. paracasei is thought to exert beneficial effects by modulating the immune response, enhancing the intestinal barrier, and inhibiting the growth of pathogenic bacteria.

Animal studies have shown that administration of L. paracasei can reduce colonic inflammation, decrease pro-inflammatory cytokines, and improve histological scores in models of chemically induced colitis. In humans, the evidence is less robust but suggestive: a few small clinical trials and pilot studies, sometimes using L. paracasei alone or in combination with other probiotics, have reported improvements in symptoms, reduced disease activity, and enhanced mucosal healing. For instance, a 2019 randomized controlled trial found that a probiotic mixture containing L. paracasei led to symptomatic relief in ulcerative colitis patients, though isolating the effect of this single strain remains challenging.

Overall, while there is scientific rationale and emerging evidence supporting the use of L. paracasei for colitis, the current clinical evidence is limited and not yet conclusive. More large-scale, well-designed human trials are needed to firmly establish efficacy and recommend routine use.