by Liz Kenyon, Physiology Assistant
What are probiotics?
Probiotics are defined as microorganisms that have beneficial effects on the host’s health. Over recent years they have attracted lots of public interest for their positive impacts on gut health and gastrointestinal (GI) diseases. Consequently, taking probiotics has made its way into the mainstream, with them readily available at many supermarkets and pharmacies as yoghurt drinks and supplements.
What is small intestinal bacterial overgrowth syndrome (SIBO)?
Our GI tract is home to a rich population of microorganisms called our gut microbiota. The gut microbiota has a significant role in maintaining healthy gut function and its disruption is associated with the development of GI diseases (1-2).
In a healthy gut, the number of microbes increases as you move down the intestinal tract, with low levels in the small bowel and high levels in the large bowel, or colon. If conditions are disrupted, bacteria can overgrow in the small bowel causing small intestinal bacterial overgrowth (SIBO) (3-4). Low stomach acid and intestinal motility issues are common causes of SIBO as stomach acid and intestine contraction patterns help keep bacteria levels low in the small bowel (3).
SIBO is associated with symptoms of irritable bowel syndrome (IBS) including bloating, abdominal pain, and diarrhoea, which may be caused by excessive intestinal gas production. SIBO is sometimes accompanied by vitamin deficiencies, most commonly seen with vitamin B12 (3).
How do we test and treat SIBO?
At the Functional Gut Clinic, we test for SIBO using hydrogen and methane breath tests according to the latest guidelines (5). These tests assess the gases in your exhaled breath at time intervals after fasting and consuming a sugary drink. Breath tests are simple and accurate as the bacteria readily digest the sugars in the drink and produce hydrogen during digestion. This hydrogen ends up in your exhaled breath, indicating the presence of SIBO (5).
The current recommended clinical treatment for SIBO is an antibiotic called Rifaximin. This can effectively eradicate SIBO while preserving the lower GI microbiota. A course of rifaximin has been shown to be better tolerated and have less severe gastrointestinal side effects compared to other antibiotics (6). However, rifaximin is not approved for the treatment of SIBO or IBS in the UK, so a course can be expensive. Alternative antibiotics can be used but these have varying rates of success and failed treatments increase the risk of antibiotic resistance. This means that there is a need for new therapies to make antibiotics more efficacious or replace them altogether.
Are probiotics helpful for SIBO?
Probiotics have been speculated to be helpful for SIBO, which sounds counterproductive by adding more bacteria to bacterial overgrowth. However, the main theory is that probiotics replace the bacteria causing SIBO and promote GI motility, helping restore a healthy microbiota, although these effects are not certain (7). In addition, probiotics may well be adding more fuel to the fire, as a study showed that people taking probiotics were more likely to produce higher levels of methane gas on breath testing (8). Also, another study showed that probiotic use in SIBO can enhance symptoms of brain fog, wind and bloating (9).
Despite this, some studies have shown that probiotics are effective at treating the symptoms of SIBO and decreasing hydrogen production (10). As there are only a few studies in this area with varying data, more evidence is needed to determine which specific probiotic strains may be helpful for SIBO.
In conclusion, SIBO causes an increase in intestinal gas production and unpleasant symptoms. Studies have shown that probiotics may be both help and hindrance for SIBO. Ultimately, there is no convincing evidence that probiotics eradicate SIBO, but antibiotics can, and they remain the most effective way to treat it.
- Jandhyala, S.M., Talukdar, R., Subramanyam, C., Vuyyuru, H., Sasikala, M. and Reddy, D.N. (2015). Role of the normal gut microbiota. World Journal of Gastroenterology, 21(29): 8787-8803
- Kim, S.M., Guevarra, R.B., Kim, Y.T., Kwon, J., Kim, H., Cho, J.H., Kim, H.B. and Lee, J.H. (2019). Role of Probiotics in Human Gut Microbiome-Associated Diseases. Journal of Microbiology and Biotechnology, 29(9): 1335-1340
- Bures, J., Cyranu, J., Kohoutova, D., Forstl, M., Rejchrt, S., Kvetina, J., Vorisek, V. and Kopacova, M. (2010). Small intestinal bacterial overgrowth. World Journal of Gastroenterology, 16(24): 2978-2990
- Rao, S.S.C. and Bhagatwala, J. (2019). Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management. Clinical and Translational Gastroenterology, 10(10): e00078
- Rezaie, A., Buresi, M., Lembo, A., Lin, H., McCallum, R., Rao, S., Schmulson, M., Valdovinos, M., Zakko, S. and Pimentel, M. (2017). Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. The American Journal of Gastroenterology, 112(5): 775-784
- Rezaie, A., Pimentel, M. and Rao, S.S. (2016). How to Test and Treat Small Intestinal Bacterial Overgrowth: An Evidence-Based Approach. Current Gastroenterology Reports, 18(2):8
- Pimentel, M., Saad, R.J., Long, M.D. and Rao, S.S.C. (2020). ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. The American College of Gastroenterology, 115: 165-178
- Mitten, Emilie MD; Goldin, Alison MD, MPH; Hanifi, Jasmine MD; Chan, Walter W. MD, MPH Recent Probiotic Use Is Independently Associated With Methane-Positive Breath Test for Small Intestinal Bacterial Overgrowth, American Journal of Gastroenterology: October 2018 – Volume 113 – Issue – p S660
- Rao SSC, Rehman A, Yu S, Andino NM. Brain fogginess, gas and bloating: a link between SIBO, probiotics and metabolic acidosis. Clin Transl Gastroenterol. 2018 Jun 19;9(6):162. doi: 10.1038/s41424-018-0030-7. PMID: 29915215; PMCID: PMC6006167.
- Zhong, C., Qu, C., Wang, B., Liang, S. and Zeng, B. (2017). Probiotics for Preventing and Treating Small Intestinal Bacterial Overgrowth A Meta-Analysis and Systematic Review of Current Evidence. Journal of Clinical Gastroenterology, 51(4): 300-311