Probiotics in IBS

 In Gastrointestinal

Keegan Sheridan, ND


Irritable bowel syndrome (IBS) is a functional disorder characterized by recurring abdominal pain and discomfort, as well as alterations in bowel habits without demonstrable pathology.1 It is prevalent in the developed world, with 10-15% of the general population affected by the disorder, skewing slightly female and under 50 years of age.2 Research of potential causes of IBS include investigations of motility, visceral sensation, brain-gut interaction, and psychosocial distress. Alterations in gut microbiota is another promising area of research. Dysbiosis (a microbial imbalance of gut microbiota) positively correlates with abnormalities of gut motility, sensitivity, and neuro-immune signaling that may contribute to the development of IBS and its associated symptoms.1

Dysbiosis in IBS

The gut microbiota is a complex ecosystem with an estimated 100 trillion cells – 10-fold more than the number of human host cells.3 The composition of this microbial community is highly variable and host-specific; it evolves throughout an individual’s lifetime and is susceptible to both exogenous and endogenous modifications.4

To more closely examine the role of dysbiosis and identify common themes in the pathogenesis of IBS, a 2017 meta-analysis comprehensively reviewed 17 case-controlled studies that identified specific gut microbiota in IBS patients from China and other regions around the world.5 From this analysis, researchers confirmed differences in gut flora between IBS patients and control subjects. More interestingly, perhaps, these differences had geographical variations. For example, while no significant geographic differences were detected in Lactobacillus, Escherichia coli, and Enterobacter strains between IBS and normal controls in regions other than China, these strains were statistically different between control and IBS groups in Chinese studies. In contrast, the studies carried out in non-Chinese regions of the world demonstrated significant changes in Bacteroides between groups, but only non-significant changes in Chinese-based studies. These data suggest the simple presence of dysbiosis in IBS may be more important than the specific species that are disrupted, and further support an environmental component in the development of this syndrome.

A Role for Probiotics

Meta-analyses published between 2009 and 2016 have concluded that probiotics are an effective treatment option for IBS.6-9 Of particular note is a significant reduction in pain scores as well as bloating and flatulence symptoms as a result of probiotic treatments. A 2014 meta-analysis of 43 randomized, controlled trials (RCTs) found that probiotics had a clear and beneficial effect on global IBS symptoms, particularly abdominal pain, bloating, and flatulence. However, data assessing specific probiotic strains and optimal duration of probiotic treatments lack the same clear conclusion. A 2016 meta-analysis of 21 RCTs concluded that single-strain probiotics at a relatively low dose and with a short treatment duration appear to be more effective than combination probiotics in improving overall symptom response and quality-of-life scores.9 However, due to the wide variation in relation to length of treatment, dose, organisms, and strengths of probiotics used in clinical trials, most analyses conclude that more research into these factors is needed.

Over the past 5 years, a small number of human clinical trials have assessed the impact of a single-strain probiotic on IBS, and may provide clinical insight into the prioritization of specific strains in treatment as well as potency and duration. A 2016 RCT of 36 newly diagnosed diarrhea-predominant IBS patients administered a Bacillus coagulans (MTCC 5856) tablet containing 2 x 109 CFU/day for 90 days.10 Clinical symptoms of IBS were evaluated though questionnaires, and the visual analog scale (VAS) was used to assess abdominal pain. Physician’s global assessment and IBS quality of life (QOL) were also considered as measures of effectiveness. At the end of the 90-day period, there were significant decreases in bloating, diarrhea, vomiting, abdominal pain, and stool frequency in the probiotic group, as compared with placebo (p<0.01). Moreover, disease severity decreased and QOL increased in the probiotic group, as compared to placebo.

A 2014 randomized, unblinded, controlled trial investigated the effect of a 6-week treatment with Lactobacillus rhamnosus GG (group 1); a diet low in fermentable, oligo-, di-, and mono-saccharides and polyols  (low-FODMAP diet) (group 2); or a normal Western diet (group 3) in 123 patients with IBS.11 Improvements in severity symptom scores were observed in both the low-FODMAP diet group and Lactobacillus rhamnosus GG treatment group. QOL scores were not altered significantly in any of the 3 groups.

In a 2016 randomized, triple-blinded trial, adult IBS volunteers received 109 or 1010 CFU of Lactobacillus acidophilus NCFM or placebo for 12 weeks.12 Of the 340 subjects who completed the trial, severity symptom scores improved in all treatment groups, including placebo. Subjects experiencing moderate–to-severe abdominal pain experienced significant improvements in pain sensations, compared to those taking placebo. Although overall severity scores improved equally with probiotic and placebo, the researchers concluded that Lactobacillus acidophilus NCFM alleviates moderate-to-severe abdominal pain.


The evidence presented in single-strain probiotic trials and meta-analyses is compelling enough to consider probiotics as part of the overall treatment approach for IBS patients. However, evidence is still insufficient to conclusively inform specific decisions regarding species of probiotics, potency, and duration of treatment. Further research to provide this level of clarity is warranted.


  1. Distrutti E, Monaldi L, Ricci P, et al. Gut microbiota role in irritable bowel syndrome: New therapeutic strategies. World J Gastroenterol. 2016;22:2219-2241.
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  8. Didari T, Mozaffari S, Nikfar S, et al. Effectiveness of probiotics in irritable bowel syndrome: Updated systematic review with meta-analysis. World J Gastroenterol. 2015;21(10):3072-3084.
  9. Zhang Y, Lixiang LI, Guo C, et al. Effects of probiotic type, dose and treatment duration on irritable bowel syndrome diagnosed by Rome III criteria: a meta-analysis. BMC Gastroenterol. 2016;16(1):62.
  10. Majeed M, Nagabhushanam K, Natarajan S, et al. Bacillus coagulans MTCC 5856 supplementation in the management of diarrhea predominant Irritable Bowel Syndrome: a double blind randomized placebo controlled pilot clinical study. Nutr J. 2016;25:21.
  11. Pedersen N, Andersen NN, Vegh Z, et al. Ehealth: low FODMAP diet vs Lactobacillus rhamnosus GG in irritable bowel syndrome. World J Gastroenterol. 2014;20(43):16215-16226.
  12. Lyra A, Hillila M, Huttenen T, et al. Irritable bowel syndrome symptom severity improves equally with probiotic and placebo. World J Gastroenterol. 2016;22(48):10631-10642.
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Keegan Sheridan, ND, graduated from Bastyr University in 2004. Since 2006, she’s worked inside the natural/organic food, beverage, and dietary supplement industries as a technical marketing expert and natural health strategist. Keegan is a member of the SFI USA (Klaire Labs) scientific advisory board, as well as a principal consultant in San Diego, CA. For more information, visit:

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