Best Probiotics for IBS: What the Latest Research Reveals

What is IBS?

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal (GI) disorder that affects at least 12% of the UK population¹. Many people who suffer from IBS experience a combination of symptoms, including abdominal pain, cramping, bloating, diarrhoea, and constipation, which can significantly affect their mental health and quality of life².

Even though many people suffer from IBS, there is currently no specific biological marker to diagnose the condition, making diagnosis challenging³. In the UK, IBS is typically diagnosed based on symptom assessment using the Rome IV or NICE guidelines, alongside ruling out other conditions like inflammatory bowel disease, coeliac disease, colorectal cancer, and anaemia. This often involves stool and blood tests to check for inflammation, abnormal blood counts, and nutritional deficiencies.

Types of IBS

There are four types of IBS²:

• IBS-C – Individuals with IBS who experience constipation, with hard and lumpy stools that are difficult to pass.
• IBS-D – Individuals with IBS who experience diarrhoea, with loose, watery stools, and a frequent need to defecate.
• IBS-M – Individuals with IBS who experience mixed bowel habits. They often experience both constipation and diarrhoea, with their symptoms fluctuating between the two.
• IBS-U – Individuals with IBS who do not clearly fit into any of the other categories, with less than 25% of their stools being hard or lumpy and less than 25% of their stools being loose or watery.

The gut microbiome and IBS

The human gut hosts trillions of microbes, which are essential for absorbing nutrients, facilitating normal immune responses, and maintaining intestinal homeostasis⁴. IBS causes changes within this ecosystem, characterised by reduced diversity, differences in microbial composition, and altered metabolic output. These changes in the gut microbiome then influence IBS in three principal ways:

• Modulation of the gut-brain axis – This network allows communication between the gut and the central nervous system. The gut microbiome produces signalling molecules, such as serotonin and short-chain fatty acids (e.g. butyrate), that influence GI motility, visceral sensation, and mood regulation⁵.
• Immune responses and intestinal barrier function – Disruption of immune signalling and barrier integrity contributes to visceral hypersensitivity and altered bowel motility, which are key features of IBS⁶.
• Different microbiota in IBS subtypes – Small intestinal bacterial overgrowth (SIBO) is more frequently seen in IBS-D and IBS-M, while increased methanogenic archaea are more commonly found in IBS-C⁷.

Probiotics and IBS: What are they and how do they help?

Probiotics are live microorganisms that specifically work by altering the gut microbiota. Clinical studies have shown that probiotics can improve IBS symptoms through a range of key mechanisms:

• Modulation of inflammation – Probiotics balance pro- and anti-inflammatory cytokines, reducing low-grade inflammation and symptoms seen in IBS⁸.
• Restoring microbiota balance – Probiotics help restore a healthy microbial balance by inhibiting harmful bacteria, increasing beneficial bacteria, and producing short-chain fatty acids, which nourish the gut lining and support barrier integrity⁹.
• Enhancing intestinal mucosal barrier function – Probiotics reduce permeability and prevent the translocation of toxins and pathogens that trigger IBS symptoms. This happens by strengthening tight junctions between epithelial cells and increasing mucus production⁹.
• Gut-brain axis regulation – Probiotics modulate the gut-brain axis by producing neuroactive compounds such as serotonin, reducing stress-induced visceral hypersensitivity and pain, improving mood, and reducing anxiety and depression¹⁰.

The best probiotics for IBS – what the research shows

There are a number of well-studied and well-tolerated bacterial species that have been shown to help manage IBS:

• Bacillus coagulans – Strains LBSC and BCP92 have shown significant improvements in IBS symptom severity, GI symptom frequency, stool consistency, and mental stress compared to placebo^11,12.
• Bifidobacterium bifidum – The MIMBb75 strain improved pain, discomfort, bloating, urgency, and quality of life compared to placebo¹³.
• Bifidobacterium lactis – The UABla-12 strain combined with Lactobacillus acidophilus DDS-1 showed improvements in abdominal pain, bowel habits, stool consistency, and quality of life¹⁴.
• Bifidobacterium longum – The ES1 strain improved symptom severity in IBS-D patients compared to placebo¹⁵.
• Lactobacillus acidophilus – A two-strain mixture improved flatus in IBS patients versus placebo¹⁶.
• Lactobacillus gasseri – The BNR17 strain improved abdominal pain in IBS patients¹⁷.
• Lactobacillus plantarum – The 299v DSM 9843 strain relieved abdominal pain and bloating in 78.1% of patients compared to 8.1% in placebo¹⁸.
• Lactobacillus reuteri – The DSM 17938 and ATCC PTA 6475 strains improved pain, bloating, gas, and inflammation¹⁹.
• Saccharomyces boulardii – This species increased IL-10 and decreased IL-8 and TNF-α in IBS-D patients, also improving quality of life⁸.

Clinical takeaways – can probiotics help IBS?

Probiotics may be a valuable addition to care plans when high-quality, evidence-backed supplements are selected. For clinicians, it’s important to guide patients with realistic expectations, encourage symptom tracking, and recognise that not all individuals will respond equally. If symptoms persist or worsen, or if red flags such as rectal bleeding, weight loss, or significant mental health issues arise, referral to a dietitian or GI specialist is advised.

While probiotics are not a cure for IBS, there is significant evidence from RCTs that supports their role in symptom management for IBS patients. Specific strains have been shown to be well-tolerated and offer substantial improvements in symptoms, including abdominal pain, bloating, diarrhoea, inflammation, and quality of life^8,11–19. Therefore, probiotics offer a natural, low-risk option that may provide meaningful relief for some individuals with IBS.

References

1. Luo M, Zhuang X, Tian Z, Xiong L. Alterations in short-chain fatty acids and serotonin in irritable bowel syndrome: a systematic review and meta-analysis. BMC Gastroenterol. 2021 Dec;21(1).
2. Burns GL, Talley NJ, Keely S. Immune responses in the irritable bowel syndromes: time to consider the small intestine. BMC Med. 2022 Mar 31;20(1).
3. Takakura W, Pimentel M. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome – An Update. Front Psychiatry. 2020 Jul 10;11.
4. Abbas Z, Yakoob J, Jafri W, Ahmad Z, Azam Z, Usman MW, et al. Cytokine and clinical response to Saccharomyces boulardii therapy in diarrhea-dominant irritable bowel syndrome: a randomized trial. Eur J Gastroenterol Hepatol. 2014 Jun;26(6):630–9.
5. Chandrasekaran P, Weiskirchen S, Weiskirchen R. Effects of Probiotics on Gut Microbiota: An Overview. Int J Mol Sci. 2024 May 30;25(11):6022.
6. Rajanala K, Kumar N, Chamallamudi MR. Modulation of Gut-Brain Axis by Probiotics: A Promising Anti-depressant Approach. Curr Neuropharmacol. 2021 Jul;19(7):990–1006.
7. Shaikh SS, Kumar S. Role of Bacillus coagulans (Heyndrickxia coagulans)BCP92 in managing irritable bowel syndrome: A randomized, double-blind, multicenter, placebo-controlled clinical trial. Medicine (Baltimore). 2024 Aug 2;103(31):e39134.
8. Gupta AK, Maity C. Efficacy and safety of Bacillus coagulans LBSC in irritable bowel syndrome: A prospective, interventional, randomized, double-blind, placebo-controlled clinical study [CONSORT Compliant]. Medicine (Baltimore). 2021 Jan 22;100(3):e23641.
9. Guglielmetti S, Mora D, Gschwender M, Popp K. Randomised clinical trial: Bifidobacterium bifidum MIMBb75 significantly alleviates irritable bowel syndrome and improves quality of life -- a double-blind, placebo-controlled study: Randomised clinical trial: B. bifidum MIMBb75 in IBS. Aliment Pharmacol Ther. 2011 May;33(10):1123–32.
10. Martoni CJ, Srivastava S, Leyer GJ. Lactobacillus acidophilus DDS-1 and Bifidobacterium lactis UABla-12 Improve Abdominal Pain Severity and Symptomology in Irritable Bowel Syndrome: Randomized Controlled Trial. Nutrients. 2020 Jan 30;12(2):363.
11. Srivastava S, Basak U, Naghibi M, Vijayakumar V, Parihar R, Patel J, et al. A randomized double-blind, placebo-controlled trial to evaluate the safety and efficacy of live Bifidobacterium longum CECT 7347 (ES1) and heat-treated Bifidobacterium longum CECT 7347 (HT-ES1) in participants with diarrhea-predominant irritable bowel syndrome. Gut Microbes. 2024 Dec 31;16(1).
12. Sadrin S, Sennoune S, Gout B, Marque S, Moreau J, Zinoune K, et al. A 2-strain mixture of Lactobacillus acidophilus in the treatment of irritable bowel syndrome: A placebo-controlled randomized clinical trial. Dig Liver Dis. 2020 May;52(5):534–40.
13. Kim JY, Park YJ, Lee HJ, Park MY, Kwon O. Effect of Lactobacillus gasseri BNR17 on irritable bowel syndrome: a randomized, double-blind, placebo-controlled, dose-finding trial. Food Sci Biotechnol. 2018 Jun;27(3):853–7.
14. Ducrotté P. Clinical trial:Lactobacillus plantarum299v (DSM 9843) improves symptoms of irritable bowel syndrome. World J Gastroenterol. 2012;18(30):4012.
15. Cruchet S, Hirsch S, Villa-López D, Moreno-Portillo M, Palomo JC, Abreu-Abreu AT, et al. Limosilactobacillus reuteri DSM 17938 and ATCC PTA 6475 for the treatment of moderate to severe irritable bowel syndrome in adults: a randomized controlled trial. Front Gastroenterol. 2024 Jan 4;2.