Aim: To determine whether Lactobacillus casei strain Shirota (Yakult) can alter small intestinal bacterial overgrowth (SIBO), as tested by the lactulose breath test, and whether this is associated with changes in symptoms in irritable bowel syndrome (IBS).
Methods: 18 patients with IBS (Rome II criteria), who showed an early rise in breath hydrogen with lactulose (ERBHAL), consumed 65 mL of Yakult daily for 6 wk. Lactulose breath test was repeated at the end of the treatment period. Symptoms were recorded daily using a 10 cm visual analogue scale.
Results: 14 patients completed the study, 9 (64%) had reversal of ERBHAL, with the median time of first rise in breath hydrogen increasing from 45 to 75 min (P = 0.03). There was no significant improvement in the symptom score with probiotic therapy, except for wind (P = 0.04). Patients commencing with at least moderate symptoms and who no longer had ERBHAL at the end of treatment, showed improvement in the overall symptoms scores [median final score 5.3 (IQR 3.9-5.9), 55% reduction; n = 6] to a greater extent than those who had had persisting ERBHAL [final score 6.9 (5.0-7.0), 12% reduction; n = 5; P = 0.18].
Conclusion: Yakult is effective in altering fermentation patterns in the small bowel, consistent with reducing SIBO. The loss of ERBHAL was associated with reduced symptoms. The true interpretation of these findings awaits a randomised, controlled trial.