Acemannan is a polysaccharide extracted from the inner leaf of Aloe vera, and has been investigated for its potential therapeutic effects in inflammatory bowel disorders (IBD), such as Crohn’s disease and ulcerative colitis. Preclinical studies (primarily in animal models) suggest that acemannan exhibits immunomodulatory and anti-inflammatory effects, such as reducing pro-inflammatory cytokines (e.g., TNF-α, IL-6) and promoting mucosal healing. For example, studies in rodents with chemically induced colitis have shown that oral or intrarectal administration of acemannan can attenuate inflammation, decrease histological damage, and improve clinical symptoms.

However, there is a lack of robust clinical evidence in humans. Only limited small-scale studies or case series have evaluated the effect of Aloe vera extracts (which contain acemannan among other compounds) in people with IBD, and the results are inconsistent. No large, well-controlled clinical trials have specifically assessed isolated acemannan in IBD patients. Thus, while there is scientific rationale based on mechanistic and animal data, the clinical evidence remains preliminary and insufficient to firmly support its use as a standard therapy for IBD.

In summary, acemannan's use for IBD is justified by early scientific findings, but the overall level of evidence (2/5) is low due to the absence of high-quality human trials.