FOS and inflammatory bowel disease: While dietary fibers are generally considered beneficial to health, some IBD patients, especially during active disease, have reduced tolerance to high fiber containing foods.131,132 Armstrong et al. demonstrated in active disease patients, that certain fibers, especially oligo-fructose (FOS), triggered pro-inflammatory cytokine IL-1β.133 Fermentation of FOS with microbiota from non-IBD or mildly affected patients reduced IL-1β secretion.