Thinking Nutrition

Managing IBS with the low-FODMAP diet and probiotics

May 31, 2022 Dr Tim Crowe Episode 100
Thinking Nutrition
Managing IBS with the low-FODMAP diet and probiotics
Show Notes Transcript

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal complaints. With no one single identified trigger or treatment, IBS can be a minefield for a person to try and get on top of. Diet changes are one area that can have a positive impact on IBS and in this podcast, I’ll look at the current evidence for different approaches with a focus on the popular low-FODMAP diet as well as probiotic supplements.

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Irritable bowel syndrome (IBS) is one of the most common gastrointestinal complaints. With no one single identified trigger or treatment, IBS can be a minefield for a person to try and get on top of. Diet changes are one area that can have a positive impact on IBS and in this podcast, I’ll look at the current evidence for different approaches with a focus on the popular low-FODMAP diet as well as probiotic supplements.

Irritable bowel syndrome is a common gastrointestinal disorder affecting up to 1 in 5 people. 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. 

The cause of IBS is unknown, but environmental factors such as changes in routine, emotional stress, infection and diet are all known to trigger an attack. With no definitive cause of IBS, treatment is mostly focused on managing the symptoms.

For a condition that affects so many people, there are few effective treatments that are well supported by evidence. One emerging dietary treatment for IBS that has gotten a lot of attention is a low-FODMAP diet.

FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols and includes carbohydrates such as lactose, fructose and fructans (which are long chains of fructose molecules such as inulin) and sugar alcohols. FODMAPs are found in many foods including wheat, milk, pears, plums, onions, garlic, and legumes.

FODMAPs can be poorly absorbed in some people, leading to their accumulation in the small intestine where they then pass into the large intestine. Once there, they can draw more water into the bowel which increases the chance of diarrhoea. FODMAPs can also increase gas production from their fermentation by colonic bacteria. These effects of FODMAPs in the bowel explain many of the symptoms reported in IBS.

So, what does the research say about following a low-FODMAP diet and improving IBS? A comprehensive systematic review from 2018 of seven randomised-controlled trials showed a reduction in global IBS symptoms through following a low-FODMAP diet. And I’ll link to this study in the show notes https://pubmed.ncbi.nlm.nih.gov/30046155

But research is never static, and since that 2018 review, there has been new research published. And this was the topic of a just-published systematic review that looked at not only the effectiveness of a low-FODMAP diet but also various species and strains of probiotics for relief of IBS symptoms. And I’ll link to the review in the show notes https://pubmed.ncbi.nlm.nih.gov/35355730

The reason probiotics were looked at in the review is 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.

So, what did this new review find? Agreeing with the building evidence base, a low-FODMAP diet did appear to offer symptomatic relief from IBS. And in a novel type of analysis asking the opposite question, they also looked at trials that used a high-FODMAP diet versus a standard diet and consequently saw a big jump in IBS symptom scores. It is almost at the stage now where a low-FODMAP diet is becoming first-line therapy for helping to manage IBS.

For probiotics, it was the Lactobacillus, Bifidobacterium, and Bacillus that appeared to be effective components in the management of IBS symptoms. But it was the evidence for Lactobacillus that was considered of the highest quality. In studies that used a combination of probiotics, these were hampered by small sample sizes. The optimal probiotic treatment duration is unclear with most studies in the analysis running for 4 to 8 weeks.

Despite the clinical benefits of the low FODMAP diet, a potentially negative impact on the gut microbiota is a concern, especially when you consider that probiotics appear to offer a benefit. Beneficial bifidobacteria concentrations are lower following a low FODMAP diet which is most likely due to reduced consumption of fermentable carbohydrates. It is a clear reason that while a low-FODMAP diet can offer symptomatic relief from IBS, it is not a diet intended to be followed long-term.

The impact of the low FODMAP diet on the gut microbiota is only one of the challenges. The low FODMAP diet is complex to follow and may lead to lower fibre, iron, and calcium intakes. Extensive food knowledge and label reading are required to identify suitable foods to eat and this is why it is advised to seek education and support from a dietitian for anyone considering trialling a low-FODMAP diet.

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 causes of IBS can be so varied and it is, after all, a syndrome. A syndrome is a group of symptoms which consistently occur together and in the case of IBS, the underlying ‘disease’ isn’t known.

Diet and lifestyle are one place to start in treating IBS and is where dietary strategies shown to improve IBS symptoms include peppermint oil, certain probiotic formulations, psyllium supplementation, avoiding trigger foods such as spicy foods and caffeine, and trialling a low-FODMAP diet all have a place.

So, let’s wrap all this up. As it is unlikely any one single dietary strategy will benefit everyone with IBS, then it may be a matter of trialling different approaches. This is where getting professional advice and support from a dietitian can help, especially with the more involved approaches such as a low-FODMAP diet.

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 if it supports it, 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.