CALB1 and irritable bowel syndrome: Compared to HCs, IBS patients had reduced densities of human peripheral choline acetyltransferase (hpChAT, p = 0.01) and calbindin (Calb, p = 0.08) NFs by 39% and 17%, respectively, with the most prominent reductions of 50% (p = 0.004) and 26% (p = 0.03) in IBS‐C.