Probiotics and IBS: Are they effective?


About 1.5–2 kg of bacteria resides in the human gastrointestinal tract. It is estimated that there are more intestinal bacteria than there are cells in the body. The dominant bacterial species in the colon are bifidobacteria and bacteroids while the flora of the small intestine is generally dominated by lactobacilli and streptococci. The bacterial flora forms protection in the intestinal mucosa against unwanted bacteria, microorganisms, and parasites. Intestinal bacteria stimulate bowel movements, help break down the remnants of food, produce several vitamins, and secrete certain hormones. They also release antioxidants from the residues of vegetables which in turn protect against chronic inflammation and various diseases. Many functions of bacteria are still unknown but research shows that taking certain strains of probiotics could potentially help fight against IBS. But how does it work and which bacterial strains you should choose?

What are probiotics?

Probiotics are so-called “good bacteria” which when administered in adequate amounts could be beneficial for the host’s health.  They can be found in certain food products such as yogurt, kefir, fermented cheese, cottage cheese, and pickled vegetables but also in the form of dietary supplements. It is good to know that there are many types of probiotics and each probiotic product contains different bacterial species or a combination of several bacterial strains. The most common species are Lactobacillus and Bifidobacteria. [2.]

Probiotic foods

How do probiotics work?

There are several theories about how taking probiotics might work against IBS.

They influence intestinal permeability

Reduced intestinal permeability is common among IBS-D patients. It was also found that patients with the IBS-D subtype often have less diverse microbial flora. Adding probiotics to the daily diet could potentially positive effect on intestinal permeability and alleviate abdominal pain.

They modulate intestinal motility

They stimulate intestinal epithelial cells to diminish diarrheal symptoms by decreasing contraction amplitude and frequency. IBS patients with subtypes D and M might benefit from increasing the intake of probiotics in their diets. If you don’t which IBS subtype you have, make sure to read our post about the different subtypes.

They help restore microbiome dysbiosis

Dysbiosis refers to the disruption of the balance between “good” and “bad” bacteria. Dysbiosis is common in IBS patients. Taking probiotics could help restore the balance. The issue is that there is no perfect microbiome and it is not clear what a ‘normal’ microbial flora should look like. But it is clear from several studies that the intestinal flora of an IBS is different from healthy individuals. [1.]

Which probiotics should you choose?

The best way to find out if probiotics work for you is to test them. Probiotics in the form of supplements (tablets, capsules, or drops) are not necessarily better than probiotics found in foods. We recommend testing one product at a time, every day, for four weeks. If there is no effect, this does not necessarily mean that probiotics do not work – but perhaps not the chosen product. Different products contain different species or strains and you may not get it right on the first few attempts!

People with IBS who want to test if probiotics work for them should also know that some products contain other ingredients that can increase IBS symptoms (such as dietary fiber, FOS, inulin, lactose, fructose, sorbitol, and xylitol). It is important to be aware that the results of many research papers differ and there is no definite conclusion on the effect of probiotics on IBS patients.


Probiotics could potentially have an effect on general symptoms such as stomach pain, bloating, and gassiness but every individual’s gut flora is unique which makes it difficult to determine which bacterial species or bacterial strains have the best effect. Future research should focus further on the identification of the bacterial strains that get the best response in specific IBS subtypes, gut compositions, and age groups. etc. For now, all you can do is keep track of what works for you.


[1.] Zhang, T., Zhang, C., Zhang, J., Sun, F., & Duan, L. (2022). Efficacy of Probiotics for Irritable Bowel Syndrome: A Systematic Review and Network Meta-Analysis. Frontiers in Cellular and Infection Microbiology12.

[2.] Simon, E., Călinoiu, L. F., Mitrea, L., & Vodnar, D. C. (2021). Probiotics, Prebiotics, and Synbiotics: Implications and Beneficial Effects against Irritable Bowel Syndrome. Nutrients13(6).