Lactobacillus and Bifidobacterium in Irritable Bowel Syndrome

Clinical Study Highlight

Lactobacillus and Bifidobacterium in irritable bowel syndrome: symptom responses and relationship to cytokine profiles

Gastroenterology 128(3):541-51

O’Mahony L, McCarthy J, Kelly P, Hurley G, Luo F, Chen K, O’Sullivan GC, Kiely B, Collins JK, Shanahan F, Quigley EM. 2005

Summary and comments by Mary Ellen Sanders, Ph.D.

It is estimated that 12% of visits to the primary care doctor and 28% of visits to a gastroenterology practice in the US are for symptoms of irritable bowel syndrome. Furthermore, an estimated 75% of people with symptoms never seek medical treatment. IBS symptoms include abdominal pain or discomfort and associated changes in stool frequency and consistency. The role of gut microbiology in the etiology of this condition is not clear, but the hypothesis that gut microbes can play a positive role in this condition has led to interest in exploring probiotics for relief of symptoms.

Toward this end, O’Mahony et al. (2005) conducted a randomized, placebo controlled study with 77 adult IBS subjects with mild symptoms (67 completed the study). Subjects received either Lactobacillus salivarius UCC4331 (1010 cfu) in a malted milk drink, Bifidobacterium infantis 35624 (1010 cfu) in a malted milk drink, or unsupplemented malted milk drink daily for 8 weeks. Symptoms (abdominal pain, bloating or distension and bowel movement difficulty) and stool characteristics were recorded daily for 8 weeks and then for an additional 4 weeks after treatment ended. In addition, subjects were assessed with a Quality of Life questionnaire and peripheral blood was drawn to determine different immune and inflammatory parameters.

The B. infantis treatment group showed several positive outcomes that were not observed with the L. salivarius or placebo groups:

  • Symptoms of abdominal pain and bowel movement difficulty were improved
  • Ratios of anti-inflammatory to pro-inflammatory (interleukin 10/interleukin 12) cytokines in peripheral blood mononuclear cells were normalized

Quality of life scores showed trends in improvement for the probiotic groups compared to the controls, but improvements in ‘health worry’ scale for the B. infantis group was the only score to reach statistical significance.

This study showed a rapid benefit (response at the end of the first week of treatment) of a B. infantis probiotic in improving symptoms for mild IBS sufferers, and clearly demonstrated that benefits are likely strain-dependent and cannot be assumed to apply to all probiotics.