Can fermented foods help your IBS?

5th April, 2024
Written by Jo Cunningham RD

Living with IBS (Irritable Bowel Syndrome) can feel like navigating a minefield of trigger foods. And fermented foods are often feared. But there are studies coming out that show including them in your diet could actually help relieve tummy troubles and support gut health in the long run.

So how can you feature fermented foods on your plate for your IBS and overall wellbeing? Read on to find out.

First, a quick recap. What actually are fermented foods?

We humans have been feasting on fermented foods for centuries. Traditionally, fermenting was a way to preserve foods and boost their flavour. But recently the health benefits and the potential power for our gut health have grabbed our attention.

Fermented foods include kefir (fermented milk), kimchi and sauerkraut (fermented cabbage and veggies). Tempeh, natto and miso (fermented soy). Kombucha (fermented tea). And even sourdough (fermented bread).

How can fermented foods help IBS?

For people with IBS, the balance of gut bacteria can often be out of whack. And that plays a role in those pesky symptoms like bloating, gas and stomach pain.

Fermented foods can help in a few ways:

  • Prebiotic Power: Fermented foods have a prebiotic effect. And that means they feed our good gut microbes.
  • Probiotic Punch: They also have a probiotic effect. Introducing new beneficial microbes into our gut. We just can’t exactly call them “probiotics” because we don’t know exactly what microbes are in there.
  • Gut Guardians: Fermented foods are filled with live bacteria and the substances they produce (called metabolites). And these can protect our gut lining. In turn, that helps our immune system and protects us against the bad guys (aka disease-causing pathogens) getting into our bodies.

Let’s take a look at the science on specific fermented foods. It’s pretty promising for managing IBS symptoms.



Kefir & Live Yoghurt Small studies suggest drinking that creamy kefir could be helpful for improving symptoms of constipation, especially for people with IBS-C (constipation-dominant IBS).
Sourdough Bread lovers: sourdough could be your solution. Research shows eating sourdough can mean more beneficial bacteria in the gut and reduced bloating and stomach pain. How? Fermenting reduces the FODMAPs – potentially good news if you’re sensitive to wheat.
Sauerkraut In a small but high quality study, participants with IBS had significantly reduced severity scores after eating sauerkraut for 6 weeks. So it looks like incorporating sauerkraut into your diet could help. Try adding in small amounts first (low FODMAP serving sizes).
Kimchi A high quality study in Korea found regularly eating kimchi was linked to significantly improved IBS symptoms like pain, bloating and not completely emptying your bowels. It also helped to normalise poo consistency and regularity. Inflammation went down and beneficial gut microbes went up too! Kimchi is a staple in Korea and the participants upped their kimchi intake to 210g a day over 12 weeks. But if you’re on a low FODMAP diet as part of your IBS treatment, just remember 75g of kimchi is “high FODMAP”. So beware of those portion sizes.
Tempeh, natto, miso (fermented soy Human studies in people with IBS are limited. But some small studies suggest eating fermented soy could reduce harmful gut bacteria and increase beneficial gut microbes. Fermenting soy beans also boosts nutrient absorption and reduces the FODMAP content. And that means it could be a great addition to an IBS-friendly diet.


What if you’re following a low FODMAP diet?

If you’re following a low FODMAP diet and you’re in the first “restriction” phase, think about the FODMAP content of fermented foods. It’s often all about the portion size.

Take cabbage for example. 75g of raw white cabbage is low FODMAP (according to Monash University, who developed the low FODMAP diet). But when it’s fermented to sauerkraut, that portion size changes to a high FODMAP food.

This doesn’t mean you have to cut out ‘high FODMAP’ fermented foods completely. Pick the right portion for you and try spacing them out so you’re not having too much at once. Use the Monash FODMAP Diet app to check FODMAP ratings or get the help you need from an IBS specialist dietitian.

For other foods, fermenting actually lowers the FODMAP rating. Soy beans are high fodmap but fermented to tempeh is low FODMAP. Other low FODMAP fermented foods include pickled gherkins and sourdough.

*But* not everyone with IBS needs to be on a low FODMAP diet. It’s actually the last thing I’d do with a client in my IBS clinic! I like to go for a much less restrictive and less stressful approach first. *Adding in* the right types of food and *spacing out* (not cutting out) your FODMAP load is often a much more effective way of tackling IBS symptoms.

5 tips for enjoying fermented foods

  1. Not currently eating fermented foods? Start slow. 1 tbsp of kefir with your breakfast. A little kimchi or sauerkraut in your sandwich or salad. Increase the amount and variety gradually to find how much you can tolerate personally.
  2. Go for small amounts of different fermented foods every day rather than large amounts less frequently. You don’t need to go overboard.
  3. Pick products that are low on the additives and preservatives.
  4. Try a new fermented food when you’re feeling calm and positive.
  5. If you’re sensitive to lactose (the main FODMAP found in dairy), keep your portion size 1 tbsp or go for lactose free yoghurts or kefir.

IBS-friendly one day meal plan *ft. fermented foods*





Overnight Oats. Mix rolled or jumbo oats with kefir or yoghurt, chia seeds, almonds and walnuts. Leave in the fridge overnight. Top with fresh or frozen berries and hemp seeds in the morning.
Lunch Sourdough Sandwich. Fill 2 slices of sourdough bread with sliced tempeh, avocado, lettuce and tomato. Add a spoonful of miso or kimchi for a flavour boost.


Saucy Salad. Toss mixed greens with a homemade dressing made from kefir or yoghurt, lemon juice, olive oil and your favourite herbs. Add fermented vegetables like pickled cucumbers or beetroot for extra flavour and crunch.

Dinner Soybean Stir-fry. Stir-fry your favourite veggies and protein (like tofu, chicken or tempeh) in a wok with a sauce made from tamari, ginger, garlic oil and a spoonful of miso. Serve with brown rice or quinoa for a hearty and nutritious meal.

What if I get gut symptoms?

It could be worth monitoring your symptoms. But remember: IBS symptoms are rarely due to one food in isolation. IBS and digestion is about your overall diet intake. Lifestyle factors like sleep, stress and movement – and your menstrual cycle for the ladies – all play a part.

Symptoms tend to trigger from FODMAP stacking (aka having too much in one go from different sources) and from having a hypersensitive gut lining.

The “nocebo” effect can be powerful too. That means if we’re expecting a symptom, we’re actually more likely to experience it.

Are fermented foods good for everyone?

The science suggests fermented foods could bring big health benefits – including for people with IBS. But ultimately there’s no one size fits all. We don’t need to go overboard with fermented foods. Let them feature as part of a balanced diet alongside a whole bunch of other nutrient-rich foods.

Some people with a histamine intolerance or food sensitivities might not get on too well with fermented foods. If you’re not sure, check with your healthcare team or a registered dietitian to get personalised advice.

About Jo Cunningham RD, Gut & IBS specialist dietitian and founder of Green Light Nutrition

Jo Cunningham is an award-winning dietitian specialising in IBS and other gut health conditions, as well as cancer nutrition. She has worked at leading hospitals, acted as the director of a leading London gut health clinic and currently runs Green Light Nutrition with a team of specialist dietitians. Personalised guidance to manage IBS symptoms is key and working with a qualified IBS dietitian can help you find what works best for you.

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