Probiotics For IBS: Exploring the Science

Irritable bowel syndrome (IBS) affects approximately 11% of the global population. However, despite its frequent occurrence, doctors still do not know what causes this digestive disorder. Genetic, environmental, and psychosocial factors may all contribute. There is also mounting evidence that the gut microbiota is involved.

The gut microbiota, also known as the intestinal flora, is the population of microorganisms that inhabit the digestive tract. A growing number of people now take probiotics to influence their gut health via the microbiota. But is it worth taking probiotics for IBS? Let’s take a look.

What Is IBS?

IBS is a functional digestive disorder. This means that it does not harm the intestines in the same way as other conditions like inflammatory bowel disease. Instead, it affects the way that the digestive system works, especially the large intestine.

Under normal circumstances, digested food is pushed through the large intestine by a series of muscular contractions. If these contractions become irregular, IBS is the result.


For example, if the contractions become too rapid, food waste can pass through too quickly and cause diarrhea. On the other hand, if the contractions become sluggish, constipation can occur.

It is possible to subcategorize IBS as follows:

  • Diarrhea-predominant (IBS-D)
  • Constipation-predominant (IBS-C)
  • Mixed diarrhea and constipation (IBS-M)

Other common IBS symptoms include:

  • Abdominal pain and cramping
  • Bloating
  • Flatulence (gas)

Some people also experience nausea and vomiting, a sensation of incomplete bowel emptying, or mucus in the stools. However, these symptoms are more unusual.

What Causes IBS?

Most experts agree that IBS symptoms occur due to miscommunication between the intestine and the brain via the gut-brain axis. However, it is unclear what causes IBS to develop initially. There appears to be a genetic link, and factors such as certain foods and stress may trigger flare-ups.

The suggestion is that people with IBS have less stable microbiota than healthy individuals.

An imbalance in the gut microbiota also appears to play a significant role. Researchers have suggested a link between gastrointestinal infections and IBS. Its symptoms are also similar to those of a condition called small intestine bacterial overgrowth (SIBO).

The suggestion is that people with IBS have less stable microbiota than healthy individuals. This has led many scientists to study the potential of probiotics for IBS.

Can Probiotics Help IBS?

Probiotics are foods or supplements containing microorganisms such as bacteria and yeasts. They increase the diversity of the intestinal flora, which has a range of possible benefits.

According to a 2015 review, probiotics may help people with IBS in the following ways:

  • Protecting against pathogenic microorganisms
  • Regulating the gastrointestinal immune system
  • Stabilizing the barrier function of the intestinal walls
  • Stimulating mucus production in the gut
  • Normalizing bowel movements
  • Reducing sensitivity to pain

Some of the most helpful probiotics for irritable bowel syndrome include the bacterial species Lactobacillus and Bifidobacterium. Within these species, there are many different subspecies, known as strains. Some products contain a single strain, while others include a combination of several.

Because of this variety, research on the subject of probiotics and IBS is highly complex. Many studies have incredibly positive results, while others show no significant benefits. We will discuss several examples in detail below.

Are Probiotics Good For IBS?

Much of the research into IBS and probiotics has yielded promising results. However, studies often involve very different methodologies, IBS subtypes, and probiotic strains. This has led some to question the reliability of the evidence. It also makes it difficult to determine whether one probiotic is better than another when treating IBS.

For example, in a 2019 review of 11 trials, just seven (63.6%) of the studies reported symptomatic improvements. Three studies evaluated the effects of a single probiotic strain, while eight involved multi-strain varieties. Based on these results, the review’s authors concluded that using a multi-strain probiotic for at least eight weeks was most beneficial.

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However, a 2020 review and meta-analysis of 59 studies suggested the opposite was true. Its authors stated that a high-dose, single probiotic taken for under eight weeks provided the best results.

Therefore, there is still much confusion surrounding how probiotics help IBS. Further research is necessary to confirm their overall effectiveness and determine an optimal treatment regimen.

Can Probiotics Make IBS Worse?

One thing that researchers agree on, at least, is that probiotics do not appear to make IBS worse. Humans have been eating probiotic foods for centuries, and adverse effects are rare.

However, it is necessary to be cautious when taking probiotic supplements. The market is not well-regulated, and low-quality products could contain dangerous contaminants.

Furthermore, certain groups of people may have adverse reactions to probiotics. They include those with compromised immune systems and serious illnesses. Possible side effects include:

  • Infections
  • The production of harmful substances
  • The transfer of antibiotic resistance genes

Therefore, it is advisable to seek medical advice before taking probiotics and carefully weigh the benefits against the risks.

How Do Probiotics Work For IBS?

It is currently unclear exactly how probiotics work for irritable bowel syndrome. For example, a 2012 study found that taking a supplement for eight weeks did not appear to alter IBS-D patients’ intestinal flora.

This finding raises many questions about how probiotics help IBS. It seems that the mechanism may not be directly linked to the microbiota, although there is currently no obvious alternative.


That said, there is evidence that probiotics can relieve many IBS symptoms, including:

  • Overall symptom improvement
  • Abdominal pain
  • Bloating and gas
  • Diarrhea
  • Constipation

Let’s look at each one in a little more detail.

Overall Symptom Improvement

A 2008 study found that treating IBS with probiotics provided overall symptomatic relief. It involved 52 participants who took either a multi-strain probiotic or placebo for eight weeks.

At the end of the study, those who took the probiotic preparation showed significant improvements in symptom severity scores. Those who took the probiotic also experienced enhanced quality of life, reduced pain days, and increased bowel habit satisfaction.

Abdominal Pain

Several studies also support the use of probiotics for stomach pain. For example, a 2008 study compared the probiotic L. acidophilus to a placebo in 40 IBS patients. After four weeks, those who took the probiotic experienced 20% greater pain reduction than the placebo group.

Another 2008 study investigated the effects of a multi-strain probiotic or placebo in 100 IBS patients. The researchers did not find the probiotic superior to placebo in terms of overall symptom reduction. However, probiotic use was associated with significant reductions in abdominal pain after four weeks. Participants with the IBS-M subtype reported the lowest pain scores.

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Finally, a 2012 multi-center trial involving 214 participants had similar results. It showed that L. plantarum reduced pain severity by 45.2% compared to 23.3% for placebo. The probiotic also improved daily bowel movement frequency.

Bloating and Gas

A 2004 study assessed a multi-strain probiotic for bloating and abdominal pain in 68 IBS patients. They took the probiotic or an inactive control for six weeks. At the end of the study, participants in the treatment group reported significant improvements in bloating and pain. Furthermore, 80% of the subjects rated the treatment as ‘effective’ or ‘very effective.’

A 2005 study investigated the benefits of probiotics for IBS gas and colonic transit. A total of 48 patients took a multi-strain probiotic for either four or eight weeks. The results indicated that the probiotic reduced flatulence scores and slowed colonic transit without altering bowel function.


In a 2016 study, researchers gave the probiotic Bacillus coagulans MTCC 5856 or placebo to 36 newly diagnosed IBS-D patients. After 90 days of treatment, those who took the probiotic experienced a significant reduction in a range of symptoms, including:

  • Bloating
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Bowel movement frequency

They also reported reductions in overall disease severity and improved quality of life. These results support the use of probiotics for IBS diarrhea and other symptoms. 


A 2016 study investigated the effects of two different probiotic blends vs. placebo in 150 IBS-C patients. One probiotic blend (F1) contained L. acidophilus and L. reuteri. The other (F2) included L. plantarum, L. rhamnosus, and B. animalis subspecies lactis. After 60 days, both probiotic groups had a significantly higher number of responders according to the following outcome measures:

  • Bloating
  • Abdominal pain
  • Constipation
  • Abdominal cramps
  • Flatulence

Overall, the F2 group had the highest number of responders, supporting the use of multi-strain probiotics for IBS constipation and associated symptoms.

Summary on Probiotics for IBS

The studies we have discussed above suggest that probiotics help IBS in several ways. However, there is a wealth of other research that has less conclusive results.

Some individuals may respond to certain strains better than others, and some may not respond at all.

The efficacy of probiotics for IBS likely depends upon a variety of factors. Some individuals may respond to certain strains better than others, and some may not respond at all. Therefore, it may be necessary to experiment with a few varieties to find one that is suitable.

In all cases, it is best to take probiotics for several weeks to gauge their effects accurately. Consumers should also ensure they choose a reputable brand and seek advice from a healthcare provider before commencing treatment.

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