Arabinogalactans are non-starch polysaccharides primarily derived from the larch tree (Larix spp.). They have been investigated for their prebiotic effects and immune-modulating properties. The rationale for their use in colitis, particularly ulcerative colitis and Crohn’s disease, centers on their ability to modulate gut microbiota and enhance production of short-chain fatty acids (SCFAs), such as butyrate, which have anti-inflammatory effects on the colonic mucosa.

Animal studies have shown that arabinogalactans can reduce inflammation in experimental models of colitis by improving intestinal barrier function, reducing pro-inflammatory cytokines (like TNF-α and IL-6), and increasing levels of beneficial gut bacteria. For example, a 2016 study in mice with chemically-induced colitis found that larch arabinogalactan supplementation led to improved colonic histology and lowered markers of inflammation.

Human data are limited. There are no large, well-controlled clinical trials specifically evaluating arabinogalactans as a treatment for colitis. Most human studies focus on their prebiotic effects in healthy individuals or their ability to stimulate immune responses. Therefore, while there is some mechanistic and preclinical evidence suggesting potential benefit, the evidence base is not robust, and clinical relevance in colitis patients remains uncertain.