Clinical IBD activity in patients with IBD with colonic disease, as defined by the PUCAI score for UC patients or the PCDAI score for CD patients, inversely correlated with the abundance of the CS-A (4S) and DS (2S4S) isomers, which are decreased in active disease (Fig. 4h,i), and positively correlated with the abundance of the CS-C (6S) and CS-E (4S6S) isomers, which are increased in active disease (Fig. 4j,k). This evidence concerns the gene CS and inflammatory bowel disease.