Barley polysaccharides inhibit colorectal cancer by two relatively independent pathways. International journal of biological macromolecules Colorectal cancer is one of the most common types of cancer worldwide that can lead to serious injury and death. Although polysaccharides are widely recognized as having antitumor activity, there has been little research on the role of barley polysaccharides (BP) in colorectal cancer. The results of our research suggest that BP (300 mg/kg) had a significant inhibitory effect on colorectal cancer, and this effect was achieved through two pathways. First, BP can directly promote the secretion of protective metabolites like 5-(4-Hydroxyphenyl)-5-phenylimidazolidine-2,4-dione and 2,3-Bis(4-hydroxyphenyl)propionitrile thereby inhibiting the cancer pathways such as ERK, PI3K, WNT, JAK-STAT, Calcium, and Cell cycle cancer pathways to alleviate inflammation. Second, BP also can enrich beneficial intestinal bacteria such as Colidextribacter, Bilophila, and UCG-003 improve the intestinal barrier, promote the production of beneficial metabolites such as 5,8-Epoxy-5,8-dihydro-3-hydroxy-8'-apo-b,y-carotenal and L-Glutamic acid, and thus inhibit cancer pathways such as ERK, PI3K, Nuclear receptor, Cell cycle, Apoptosis and TGF-β. In conclusion, our findings suggest for the first time that BP can alleviate colorectal cancer by two relatively independent pathways: direct action and indirect action via the gut microbiota on both colon tumor cells and microbiota. 10.1016/j.ijbiomac.2024.133820