This randomized, double-blind, placebo-controlled, multi-center study investigated the clinical efficacy of two probiotic strains on abdominal pain severity and symptomology in irritable bowel syndrome (IBS). Three hundred and thirty adults, aged 18 to 70 years, with IBS according to Rome IV criteria were allocated (1:1:1) to receive placebo, Lactobacillus acidophilus DDS-1 (1 × 1010 CFU/day) or Bifidobacterium animalis subsp. lactis UABla-12 (1 × 1010 CFU/day) over six weeks. The primary outcome was the change in Abdominal Pain Severity - Numeric Rating Scale (APS-NRS). Over the intervention period, APS-NRS was significantly improved in both probiotic groups vs. placebo in absolute terms (DDS-1: -2.59 ± 2.07, p = 0.001; UABla-12: -1.56 ± 1.83, p = 0.001) and in percentage of significant responders (DDS-1: 52.3%, p < 0.001); UABla-12 (28.2%, p = 0.031). Significant amelioration vs. placebo was observed in IBS Symptom Severity Scale (IBS-SSS) scores for L. acidophilus DDS-1 (-133.4 ± 95.19, p < 0.001) and B. lactis UABla-12 (-104.5 ± 96.08, p < 0.001) groups, including sub-scores related to abdominal pain, abdominal distension, bowel habits and quality of life. Additionally, a significant normalization was observed in stool consistency in both probiotic groups over time and as compared to placebo. In conclusion, L. acidophilus DDS-1 and B. lactis UABla-12 improved abdominal pain and symptom severity scores with a corresponding normalization of bowel habits in adults with IBS.
Keywords: Randomized controlled trial; abdominal pain; bowel habits; irritable bowel syndrome; microbiome; probiotic.