Irritable bowel syndrome is one of the most common gastrointestinal complaints. With no single identified trigger or treatment, IBS can be a minefield for a person to try and get on top of. Dietary changes like a low-FODMAP diet, supplements and stress modification all have a role to play. Another emerging treatment for IBS are probiotics. Probiotics may improve IBS symptoms by changing the gut microbiota and their metabolite production which can change gut motility, inflammation and gut hypersensitivity. In this podcast, I’ll look at the evidence for the use of probiotic supplements in IBS.
Irritable bowel syndrome is a common gastrointestinal disorder with some estimates saying it could affect up to 1 in 5 people. The prevalence of IBS tends to be higher in developed countries, and it is more commonly seen in women than in men. Symptoms of IBS include abdominal bloating, pain, flatulence, diarrhoea and altered bowel habits. The condition can be difficult to diagnose because other conditions share the same symptoms.
As a gastroenterologist once said to me, IBS is code for “We don’t know”. And that is a fair call to make as the underlying cause or causes of IBS can be so varied and it is, after all, a syndrome which is a group of symptoms that consistently occur together and in the case of IBS, the underlying ‘disease’ isn’t known. Environmental factors such as changes in routine, emotional stress, infection and diet are all known to trigger a flare-up of IBS.
With no definitive cause of IBS, treatment is mostly focused on managing the symptoms. Dietary changes such as increasing the amount of fibre eaten, eliminating potential ‘problem foods’ such as gas-producing beans or cabbage, spicy foods, removing dairy foods and wheat from the diet or following a low-FODMAP diet can all work for some people. A range of medications are sometimes prescribed to manage IBS, while stress management techniques can also help some people.
One area of interest is the role of probiotics as they may help improve IBS symptoms by inducing changes in the gut microbiota and their metabolite production. Probiotics can also interact with the intestinal immune system and the nervous system. Probiotics thus may modulate gut motility, inflammation and gut hypersensitivity.
Although multiple probiotics have been tested in IBS in randomised controlled trials, it still isn’t clear which probiotic strains, either alone are as a combination, may be the most beneficial. But as more and more research trials are published, there is greater resolution of important aspects to the question such as larger sample sizes in trials, comparison of similar IBS-related outcomes, and evaluation of a similar pool of probiotic bacteria and doses.
This was the focus of a recently published and updated systematic review that could incorporate newly published trials as part of evaluating the wider evidence base. The review included all up 82 randomised controlled trials that enrolled over 10,300 people over the age of 16 who had been diagnosed with IBS. Every trial compared probiotic supplementation to a placebo. And the studies included participants with all subtypes of IBS where either diarrhoea, constipation or fluctuation between the two was the predominant symptom presentation.
As for the probiotics used, about half of the studies used a combination of probiotic bacteria while the other half used single-strain probiotics. The genera of probiotics used in order of most common included Lactobacillus, Saccharomyces, Bifidobacterium, Bacillus, Streptococcus, Escherichia, Blautia and Clostridium. And I’ll link to the study in the show notes. https://pubmed.ncbi.nlm.nih.gov/37541528
So, what were the findings? Global symptoms of IBS were improved with the use of a combination of probiotics and also for certain individual strains with ones from the genera of Lactobacillus, Bacillus and Escherichia strains showing the greatest benefit.
For abdominal pain specifically, there was some benefit seen with combination probiotics, Lactobacillus strains, Saccharomyces strains, Bifidobacterium strains and Bacillus strains when compared to placebo.
However I need to add that in most cases, the grading of evidence was rated at a very low certainty level. And many of the studies had noteworthy sources of bias. So it was not quite a glowing report card for probiotics based on the quality of evidence, but it still showed a signal that some benefit was being seen and where combination approaches or specific strains worked best.
On a positive note, the incidence of adverse events and side effects was no greater in people who took probiotics compared to people who took the placebo.
So, let’s wrap all this up. The research field for the use of probiotics in IBS is mixed. There also is not a lot of clarity for which bacterial species and the form they are found in are best to use. So, for professionals listening, it is very unhelpful to advise someone with IBS to ‘take a probiotic’ without specifying what strain and to be able to source the evidence for such as many of the effects of probiotics come down to what strain is being trialled for what condition.
If you have IBS and are considering trialling a probiotic supplement, then it may be a case of experimenting with different strains or a combination of them and importantly, you should trial it consistently for at least 4 to 6 weeks before evaluating its effectiveness.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.