A randomized, double-blind, crossover, placebo-controlled trial assessing the efficacy and the mechanism of action of Lactobacillus paracasei CNCM I-1572 in patients with IBS showed initial improvements in IBS symptoms, a significant reduction in the genus Ruminococcus, an increase in fecal SCFAs such as acetate and butyrate, and a reduction in the pro-inflammatory cytokine interleukin-15 [126]. Here, IL15 is linked to irritable bowel syndrome.