Irritable Bowel Syndrome, Inflammation, and Probiotics

By Jun Kim Ph.D.


As a major mechanism of cellular defense in the immune system, the inflammation usually protects the body from pathogens by inhibiting their growth and actively removing them by recruiting immune cells. However, when it goes beyond a tolerable limit it can damage the body. Dysregulated inflammation has been implicated in different diseases such as autoimmune disease and cancer. In addition to small intestine bacterial overgrowth (SIBO) and gut motility, inflammation is another important concept in irritable bowel syndrome (IBS). It was mentioned here that IBS does not produce the destructive inflammation that is found in inflammatory bowel disease (IBD). However, studies do suggest less severe dysregulation of inflammation [1]. This article will discuss some of the recent findings for the association between inflammation and IBS, and the potential benefits of probiotics for IBS through regulating inflammation.
Although routine examinations do not show significant inflammatory abnormalities in IBS patients, more sensitive and quantitative analyses have indicated alterations [2]. Studies have shown low-grade inflammation throughout the small intestine and the colon in IBS patients [3–5]. They exhibit an increase of certain immune cells, such as mast cells, lymphocytes, dendritic cells [6, 7]. Also, an increased level of inflammatory molecules, including interleukins and histamine, has been detected, which is known to cause an alteration in gut motility and sensory perception [4, 8]. The reported evidence for the association between inflammation and IBS suggests that treating low-level inflammation may improve IBS symptoms. Based on this idea different clinical studies have been conducted, but currently, the benefits of this approach do not seem to be clear [9, 10]. As discussed in a previous article, this may be due to the fact there are multiple causes for IBS and an approach that acts through multiple mechanisms may be required.






Bifidobacterium Infantis Probiotic

A study that investigated the Bifidobacterium infantis probiotic on rats showed that the treatment may have had a role in reducing pro-inflammatory markers [11]. O’Mahony et al. performed a study where the patients diagnosed with IBS were treated with B. infantis [12]. This treatment group showed a significant reduction in the symptoms of IBS. Also, an inflammatory marker (the interleukin-10/-12 ratio), which is abnormal in IBS patients in the proinflammatory state, was normalized in the treatment group, suggesting that the mechanism of action of this particular probiotic may involve an immune-modulating effect.
IBS is a multifactorial disorder, and some of the potential causes were discussed in this article and the two previous articles on IBS (IBS + Gut Motility). Currently, the relationship between the factors contributing to IBS is not clear, and treating only one of the factors may lead to limited efficacy. In this regard, probiotics treatment may be a particularly important option to be investigated as it has been demonstrated to act through a number of different mechanisms.
Disclaimer: The above article is sponsored by Thryve, the world’s first Gut Health Program that incorporates microbiome testing and personalized probiotics to ensure a healthier gut, happier life, and a brighter future.


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[1] Collins, S. M. (1994) Irritable-Bowel-Syndrome Could Be an Inflammatory Disorder, Eur J Gastroen Hepat 6, 478–482.
[2] Sinagra, E., Pompei, G., Tomasello, G., Cappello, F., Morreale, G. C., Amvrosiadis, G., Rossi, F., Lo Monte, A. I., Rizzo, A. G., and Raimondo, D. (2016) Inflammation in irritable bowel syndrome: Myth or new treatment target?, World J Gastroenterol 22, 2242–2255.
[3] Chadwick, V. S., Chen, W. X., Shu, D. R., Paulus, B., Bethwaite, P., Tie, A., and Wilson, I. (2002) Activation of the mucosal immune system in irritable bowel syndrome, Gastroenterology 122, 1778–1783.
[4] Barbara, G., Stanghellini, V., De Giorgio, R., Cremon, C., Cottrell, G. S., Santini, D., Pasquinelli, G., Morselli-Labate, A. M., Grady, E. F., Bunnett, N. W., Collins, S. M., and Corinalidesi, R. (2004) Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome, Gastroenterology 126, 693–702.
[5] Weston, A. P., Biddle, W., and Miner, P. B. (1991) Terminal Ileal Mucosal Mast-Cells in Irritable-Bowel-Syndrome, Clin Res 39, A716-A716.
[6] Dunlop, S. P., Jenkins, D., and Spiller, R. C. (2003) Distinctive clinical, psychological, and histological features of postinfective irritable bowel syndrome, Am J Gastroenterol 98, 1578–1583.
[7] Long, Y., Wang, W., Wang, H., Hao, L., Qian, W., and Hou, X. (2012) Characteristics of intestinal lamina propria dendritic cells in a mouse model of postinfectious irritable bowel syndrome, J Gastroenterol Hepatol 27, 935–944.
[8] Gwee, K. A., Collins, S. M., Read, N. W., Rajnakova, A., Deng, Y., Graham, J. C., McKendrick, M. W., and Moochhala, S. M. (2003) Increased rectal mucosal expression of interleukin 1 beta in recently acquired post-infectious irritable bowel syndrome, Gut 52, 523–526.
[9] Clarke, G., Cryan, J. F., Dinan, T. G., and Quigley, E. M. (2012) Review article: probiotics for the treatment of irritable bowel syndrome — focus on lactic acid bacteria, Aliment Pharmacol Ther 35, 403–413.
[10] Dunlop, S. P., Jenkins, D., Neal, K. R., Naesdal, J., Borgaonker, M., Collins, S. M., and Spiller, R. C. (2003) Randomized, double-blind, placebo-controlled trial of prednisolone in post-infectious irritable bowel syndrome, Aliment Pharmacol Ther 18, 77–84.
[11] Desbonnet, L., Garrett, L., Clarke, G., Bienenstock, J., and Dinan, T. G. (2008) The probiotic Bifidobacteria infantis: An assessment of potential antidepressant properties in the rat, J Psychiatr Res 43, 164–174.
[12] O’Mahony, L., McCarthy, J., Kelly, P., Hurley, G., Luo, F. Y., Chen, K. S., O’Sullivan, G. C., Kiely, B., Collins, J. K., Shanahan, F., and Quigley, E. M. M. (2005) Lactobacillus and Bifidobacterium in irritable bowel syndrome: Symptom responses and relationship to cytokine profiles, Gastroenterology128, 541–551.

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