You’ve probably heard someone recommend fermented foods are a good idea for improving gut health, but are fermented foods good for IBS?

What are fermented foods?

Fermented foods include foods like:

  • yoghurt (fermented milk)
  • kefir (fermented milk)
  • sauerkraut (fermented cabbage)
  • kimchi (Korean fermented spicy vegetables)
  • tempeh (fermented soya)
  • kombucha (fermented tea)

The benefits of fermented foods

Fermentation of foods dates back to preserving fresh produce before refrigeration. Our modern way of living with freezers and chilled goods, as well as plentiful supplies in the shops means fermenting foods fell out of fashion for a while.

The process of fermentation involves beneficial micro-organisms breaking down the sugars and starches, which helps preserve the foods.

The beneficial bacteria and yeasts remain in the food when we eat it, and they are good for us, sometimes called probiotics. Probiotics have been shown in several studies to improve gut bacteria diversity, support the integrity of gut mucus membranes and help support immunity.

Fermentation can help some people with IBS by partially pre-digesting the sugars. For example the fructans in bread were found to be lower when the dough was fermented with a specific strain of yeast. 


This may be why sourdough can be easier to digest for some people than other breads, because the fermentation breaks down some of the starch.

But wait! It’s not all good news…

Fermenting can increase FODMAPS

Low FODMAP dieters look out! Some fermented foods can actually be higher in FODMAPS than the unfermented version. (Read more about FODMAPs and IBS)





Well, white cabbage is low in FODMAPS, but through the fermenting process the fructose is released and converted to mannitol (a Polyol). It’s considered low FODMAP up to a tablespoon, but high FODMAP at 75g / quarter of a cup. This could be the same for kimchi.


But red cabbage sauerkraut is still low in FODMAPS.
The bottom line is – portion sizes are important, sometimes a small amount of a fermented food will be ok for you, but a large amount causes IBS symptoms.


Fermented foods for IBS

As always, whether fermented foods will suit you or not depends on your individual symptoms and experience of IBS.
One food isn’t going to make or break your symptoms, it’s all about context and your overall diet patterns.
Fermented foods can be good for adding a diversity of probiotic bacteria, increasing fibre (e.g. sauerkraut) or other nutrients (e.g. calcium from kefir), and to increase diet variety.


Should you eat sauerkraut if you have IBS?

Eating fermented cabbage may help improve your IBS symptoms.

  • A small study in 2018 showed eating sauerkraut for 6 weeks improved the IBS symptom severity and gut microbiome (it was only 34 people). This could be due to the positive effect of adding beneficial microbes into the gut. Even the pasteurised version of sauerkraut (with no live bacteria) had a significant beneficial impact on the gut bacteria which is probably down to the pre-biotic content of the cabbage (fibre feeds the beneficial bacteria).
  • Another study in 2022 reduced symptoms of IBS when participants ate 210g kimchi for 12 weeks. Kimchi is Korean fermented cabbage and participants had improvement in defecation time and stool type. 

Is Kefir better than milk for IBS? 

Fermented dairy may be easier for you to digest if you struggle with dairy intolerance. Live bacteria break down lactose in the fermentation process. One study found yogurts and kefir reduced the perceived severity of flatulence by 54% to 71% compared to milk.

(This won’t help you if you have a dairy allergy though, you still need to avoid kefir.)


Low FODMAP fermented foods

Also – if you’re dairy free you can sometimes find coconut or soy kefir.

However, some people with IBS will also react to these products as well.

Can I buy fermented foods for IBS?

  • It can be cheaper to make your own – and relatively easy.
  • If you buy fermented foods check your product isn’t pasteurised which means all the beneficial bacteria will be killed off. Look out for markings of Live bacteria or probiotic bacteria on the label.
How to start using fermented foods for IBS

Start slowly. Don’t eat a whole jar of sauerkraut or gulp down a whole carton of kefir if you haven’t tried it before. Start with a small amount, notice any reactions.

Fermented foods can be a great way to support a healthy balanced diet. If they don’t work for you, it’s not essential to include them.

Hi I'm Anna Mapson, registered Nutritional Therapist.

I help people with IBS and SIBO get control of unpredictable gut symptoms to find long term relief from painful and embarrassing IBS without restrictive dieting.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • develop better digestion and more energy

Find more about my 3 month 1:1 Gut Reset programme

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