Fermented foods, gut health and the Low FODMAP diet

I was asked to write a blog post about FODMAP-friendly gut repairing and fermented foods. I thought I’d cover both topics together as they are actually connected.


There’s one important point to understand first: if you have IBS, you cannot repair the gut and miraculously rid yourself of the condition. People with IB do not have anything physically wrong with the gut. There is no inflammation, there are no cysts and no damage to your gastrointestinal tract. It can be frustrating when a gastroenterologist says your colonoscopy and/or a gastroscopy tests came back clear – you wanted a diagnosis of some disease that’s cased all your troubles! But being disease-free is a good thing.


So what causes your symptoms? We do know that certain FODMAPs are highly osmotic, which means that they draw water into the intestine. Because of this, they create pressure within the gut and often cause diarrhoea. FODMAPs are fermented by the bacteria that naturally live in the large intestine, which can create large volumes of gas. For those with sensitive nerve endings (e.g. IBS sufferers) this can result in IBS symptoms.


Let’s get two things clear: FODMAPs are NOT damaging your intestine, and malabsorption of FODMAPs does NOT result in nutritional deficiencies.



We do know that some high-FODMAP foods are actually prebiotics and are really beneficial for the gut. I’m talking about the inulin, fructans and GOS found in cereal products like wheat and rye, as well as pulses, garlic, onion and artichokes. Prebiotics are a substrate that is used by the host and gives health benefits. This is why you should only do the elimination diet for 2-6 weeks, as cutting out these foods (after only 4 weeks) can change your microbiota. We don’t actually know the impact of this change in microbiota on our long-term health. So please, don’t eliminate foods unnecessarily. A little gas production is actually normal and a sign of a healthy gut. Include foods that you can tolerate!


Another dietary aspect of gut health is resistant starch. As its name suggests, it actually doesn’t get digested in the small intestine – it actually passes into the large intestine, where the bacteria break it down and produce gas. It is thought that resistant starch assists the microbiome, but there’s so much more we need to lean about this. Resistant starch is found in unripe bananas, al-dente pasta, cooked and cooled potato and other grains. We know that 1 unripe banana is low FODMAP, ½ cup of wheat pasta is low FODMAP and potato is low FODMAP. Including these in your diet is beneficial.


There’s lots of talk these days about fermented foods: sourdough bread, sauerkraut, kimchi, kombucha, kefir etc. A recent article https://isappscience.org/wp-content/uploads/2017/01/Marco-health-benefits-fermented-foods-ISAPP-rev-17.pdf published in 2017 suggests that fermentation can enhance or alter the nutritive and health properties of the food. Fermented foods can enhance health in a similar way to probiotics. The microbes found in fermented foods actually introduce new compounds to the foods and deliver it directly to the gut, making them an important dietary source of live micro-organisms.


My second attempt at sourdough bread - it was so scrumptious! 

My second attempt at sourdough bread - it was so scrumptious! 

You might wonder whether these fermented “goodies” can fit into the low FODMAP diet. The good news is the process of fermentation affects the FODMAP content of foods. During fermentation, micro-organisms like lactobacilli actually “feed” on FODMAPs like fructans and GOS, lowering the fructan and GOS content of that product. This is why white bread is low FODMAP at 1 slice, but sourdough white bread is low FODMAP at 2 slices. One issue is that the process can also cause an increase in the polyol mannitol, which is a by-product of fermentation. Sourdough which has been left to rise for 2-24hours is low FODMAP, but becomes high FODMAP if it has been left for longer than 24hours. Interesting hey?


White sauerkraut (fermented cabbage) is low FODMAP at 1tbs and red is low FODMAP at ½ cup. Kombucha (fermented tea) is an interesting one – Monash has suggested 180ml is low FODMAP; however FODMAP Friendly suggest it’s high FODMAP at quantities greater than 30ml. For products with such a discrepancy, it may be best to limit your intake to the smaller amount until you are through the elimination phase of the diet. When you’re in the reintroduction phase, you can test these products to see what level your body can tolerate. Including safe low-FODMAP serves of fermented foods is very healthy for your gut. If you haven’t had them before, start out small and always check back with the Monash Low FODMAP diet ap on the safe serves.


If you want to read more about fermenting, read “Ferment for Good”, a book by an absolutely inspiring dietitian, Sharon Flynn. It talks about fermentation and how you can do it at home. She also runs workshops –check her out here: https://www.thefermentary.com.au


My very first sauerkraut - it's still fermenting so I haven't tried it yet! Sharon Flynn's "Ferment For Good" book gave me the recipe, include hints and tips that I needed to give this a go! 

My very first sauerkraut - it's still fermenting so I haven't tried it yet! Sharon Flynn's "Ferment For Good" book gave me the recipe, include hints and tips that I needed to give this a go! 

As with all areas of nutrition, there is no one-size-fits-all solution and no one food that’s going to fix everything. The key is to eat a wide variety of foods, including foods containing resistant starches, fructans and GOS and also include some fermented products (if you like them). Don’t forget to add some dairy products or alternatives, some fruit and vegetables, lean meats or non-meat alternatives if you’re vego! These foods all contain important nutrients and are great for health.*


If you have a topic you’d like me to blog about, please comment below :) 

* As always, if you have specific food allergies or a condition like coeliac, avoid any foods you cannot tolerate.


- Jenna