Fermented Foods for IBS Symptom Relief?

Living with Irritable Bowel Syndrome (IBS) often feels like tiptoeing around a minefield of trigger foods. Fermented foods are often feared by many with IBS. They are now emerging as potential allies, however, in IBS symptom relief. This article delves into the potential benefits of incorporating fermented foods into your diet to help manage your IBS symptoms.

What exactly are fermented foods?

Fermented foods have been staples in human diets for centuries, typically used as a method of food preservation and flavour enhancement. There has been a huge trend towards including fermented foods in the diet for their gut health benefits.

Examples include:

  • Kefir (fermented milk)
  • Kombucha (fermented tea)
  • Sauerkraut (fermented cabbage)
  • Tempeh (fermented soy)
  • Natto (fermented soy)
  • Miso (fermented soy)
  • Kimchi (fermented spicy vegetables)
  • Sourdough (fermented bread)

The role of fermented foods in IBS

Imbalances in gut bacteria can potentially exacerbate symptoms such as bloating, gas and abdominal discomfort commonly experienced by someone with IBS. Including fermented foods can be helpful in different ways. Firstly, they have a prebiotic effect that nourishes existing gut microbes to help them thrive. Secondly, they have the benefit of introducing new beneficial bacteria to the gut microbiome. Furthermore, they have been associated with strengthening of the gut’s mucosal lining (which can get a bit leaky in IBS), as well as supporting the immune function and shielding against invading pathogens. 

If you’re currently in the first phase of the low FODMAP diet (a proven therapeutic treatment for IBS), it’s important to be aware that the FODMAP content of fermented foods can be different to their non-fermented versions. Monash University has tested the FODMAP content of fermented foods. Their traffic light system in the mobile app can help guide you as to appropriate serving sizes.

Interestingly, whilst a cup of raw cabbage is considered low FODMAP, its fermented counterpart, sauerkraut, is high FODMAP in the same serving size. Conversely, fermented soy and wheat foods show a reduction in FODMAPs through the fermentation process. Confusing? It can be. That’s where IBS specialist dietitian can guide you.

Whilst fermented foods offer promise for IBS management, it’s important to note that not everyone requires a low FODMAP diet. In clinical practice, my team and I prefer a less restrictive approach, focusing on incorporating the right foods and spacing out FODMAP intake to manage symptoms effectively. 

It is also worth mentioning that fermented foods may not be suitable for everyone, particularly those with histamine intolerance or food sensitivities. Consulting a registered dietitian can provide guidance in such cases. 

Exploring the evidence for fermented foods

Research highlights the potential of specific fermented foods in managing IBS symptoms. 


A 2018 randomised double-blind trial demonstrated a significant reduction in IBS severity scores after six weeks of sauerkraut consumption, suggesting its potential in alleviating symptoms such as bloating and discomfort. Two tablespoons (23g) of sauerkraut is classified as a low FODMAP portion size. 


A randomised, double-blind placebo-controlled study a couple of years ago found that regular kimchi consumption led to significant improvements in IBS symptoms, stool frequency, stool consistency, and gut microbiota composition. ⅓ of a cup (47g) is classified as a low FODMAP serving of kimchi.

Fermented Soy Foods

Whilst research is limited in humans, small studies suggest that fermented soy foods like tempeh, natto, and miso, may positively influence the balance of gut microbes (enhancing the good ones and lowering the harmful ones). This make these a nutrient-dense and promising addition to an IBS-friendly diet. A tablespoon of miso paste is low FODMAP, as is a cup (170g) of firm tofu, or a slice (100g) of tempeh.

Sourdough Bread

Studies suggest that sourdough consumption can enrich beneficial gut bacteria while reducing symptoms like bloating. Bread is something many of my IBS clients struggle with due to the high fructan (FODMAP) content. The FODMAP content in sourdough is lower than that of regularly produced bread. 2 slices of spelt sourdough (52g) is low FODMAP compared to 1 slice of whole wheat bread. This makes it a great option for IBS breadlovers!

Kefir and Yoghurt

Scientific findings suggest that kefir may alleviate constipation in individuals with IBS-C. If an individual is sensitive to lactose (the FODMAP in dairy), where symptoms are often bloating and loose stools, then including a tablespoon of kefir or yoghurt can help keep symptoms at bay whilst still including these foods for their potential health benefits. Lactose-free yoghurts and kefirs are also available these days which are a wonderful low FODMAP alternative to ensure no one misses out on these nutritious staples.

Incorporating Fermented Foods

For those new to fermented foods, start with small servings. If you’re in the first phase of the low FODMAP diet, use the Monash app to help guide you with appropriate portion sizes. Aim to gradually increase the portion size and the variety of fermented foods over a period of a few weeks. Choose fermented products which ideally don’t have additives and preservatives. 

It’s important to remember that IBS symptoms often stem from a combination of factors, including FODMAP stacking and heightened gut sensitivity. Non-diet factors can play a huge role in IBS too. It’s best to ask for guidance from an expert who will tailor recommendations based on your own unique needs. 

Here’s some suggestions on how to incorporate fermented foods into your day or week:


Serve a nut and see rich granola with chia seeds, berries and kefir or yoghurt. For some added fibre and plant protein, serve with hulled hemp seeds. Alternatively add some yoghurt or kefir into a smoothie or overnight oats. 


Try a spelt sourdough sandwich and consider a filling of sliced tempeh, avocado, lettuce and tomato. Alternatively, add fermented vegetables like pickled cucumbers, kimchi or beetroot to a salad; or stir in some kefir or yoghurt to a nourishing soup. 


If you’re a stir-fry fan, try some tofu marinated in tamari, and ginger and garlic oil. Alternatively marinate some salmon in miso, balsamic vinegar and tamari. Serve with wholegrain rice noodles or brown rice and a rainbow of vegetables for a nourishing and satisfying evening meal.


Integrating fermented foods into your diet can be a promising approach for addressing IBS symptoms and improving gut health. Whilst fermented foods boast a spectrum of health benefits, it’s important to acknowledge that dietary strategies should be customised to suit individual needs, preferences and tolerances. An IBS specialist dietitian can help you incorporate these fermented foods into your diet while effectively managing your symptoms. 

For expert advice, reach out to the team at Green Light Nutrition who can talk to you about incorporating more of these gut-friendly foods into your diet. 


Valentino V, Magliulo R, Farsi D, et al. Fermented foods, their microbiome and its potential in boosting human health. Microb Biotechnol. 2024;17(2):e14428. doi:10.1111/1751-7915.14428


Leeuwendaal NK, Stanton C, O’Toole PW, Beresford TP. Fermented Foods, Health and the Gut Microbiome. Nutrients. 2022;14(7):1527. Published 2022 Apr 6. doi:10.3390/nu14071527


Kim, Hee-Young et al. “Kimchi improves irritable bowel syndrome: results of a randomized, double-blind placebo-controlled study.” Food & nutrition research vol. 66 10.29219/fnr.v66.8268. 23 May. 2022, doi:10.29219/fnr.v66.8268


Garnås, Eirik. “Fermented Vegetables as a Potential Treatment for Irritable Bowel Syndrome.” Current developments in nutrition vol. 7,3 100039. 18 Feb. 2023, doi:10.1016/j.cdnut.2023.100039  


Shahbazi, Roghayeh et al. Anti-Inflammatory and Immunomodulatory Properties of Fermented Plant Foods. Nutrients vol. 13,5 1516. 30 Apr. 2021, doi:10.3390/nu13051516 


Polese B, Nicolai E, Genovese D, et al. Postprandial Gastrointestinal Function Differs after Acute Administration of Sourdough Compared with Brewer’s Yeast Bakery Products in Healthy Adults. J Nutr. 2018;148(2):202-208. doi:10.1093/jn/nxx049


Castellone V, Bancalari E, Rubert J, Gatti M, Neviani E, Bottari B. Eating Fermented: Health Benefits of LAB-Fermented Foods. Foods. 2021; 10(11):2639. https://doi.org/10.3390/foods10112639


González, S et al. “Fermented Dairy Foods: Impact on Intestinal Microbiota and Health-Linked Biomarkers.” Frontiers in microbiology vol. 10 1046. 24 May. 2019, doi:10.3389/fmicb.2019.01046

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