Your guide to fermented foods and FODMAPs

Fermented food is a hot topic, with fermented products such as kombucha and kimchi emerging on the trendiest of cafe menus.

The benefits offered by fermented foods are reported as anything from improving your gut health to treating major chronic disease. So, with an increasing focus on gut health and the impact of the gut microbiome on many aspects of our wellbeing – the potential benefits of fermented food are exciting!

But what is all the fuss about, and is there evidence to back it up?

What is a fermented food?

Fermentation is a natural process in which microorganisms including yeast, bacteria and fungi turn a compound (usually a carbohydrate like a starch or sugar) into an alcohol or acid. For example, yeast converts sugar into alcohol. Examples of fermented foods include bread, yoghurt, cheese, sauerkraut, and kombucha.

Why ferment food?

Fermentation has been used to make food such as wine and cheese long before it was really understood. Fermenting food has a range of uses and functions, including:

• Food preservation e.g. pickled vegetables.
• Produces carbon dioxide e.g. to leaven bread, carbonated drinks.
• Adds good microbes to the gut (fermented foods containing ‘probiotics’) e.g. yoghurt, miso, kefir.
• Assists digestion e.g. fermentation makes products such as yoghurt and cheese easier for those with lactose intolerance to digest. The lactose normally present in milk is broken down into simple digestible sugars.
• Breaks down anti-nutrients. Anti-nutrients interfere with digestion and absorption of nutrients that we need! E.g. phytic acid in legumes/grains interferes with the absorption of iron and zinc.

What are the health benefits?

The health benefits spruiked around fermented foods come down to the probiotics they contain. Probiotics are living microorganisms (bacteria, fungi, yeasts), or simply ‘good bacteria,‘ that in ample amounts can have health benefits. Studies have shown evidence that probiotics can improve digestion, relieve IBS symptoms, improve immune function and protect against disease.

Like the collection of microorganisms in each person’s gut, the probiotics found in different foods vary greatly. So, it is hard to generalise the benefits of different fermented foods, and the evidence for some is stronger than others. Strains of lactobacillus and bifidobacterium are most often used with strong evidence for their effectiveness and are found in yoghurt and Yakult.

Fermented foods and FODMAPs

The FODMAP content of some foods is the same whether they are fermented or not, whilst the FODMAP content of others is increased by fermentation e.g. white cabbage.

So, it is possible to enjoy fermented foods while low FODMAP, but it is important to check the appropriate serve size and other ingredients which may have been added. Some examples of appropriate serve sizes are:

• 1 tbsp white cabbage sauerkraut
• ½ cup fermented red cabbage
• 180ml kombucha
• 1 tub goats milk yoghurt

Should you be eating fermented food?

Fermented foods seem to have some health benefits, and the evidence is particularly strong for some. However, you should include them in the context of a healthy diet, exercise, adequate sleep and stress management.

Regardless of the health benefits of fermentation, yoghurt is a great go-to breakfast or snack, kombucha makes a delicious sweet treat, and sauerkraut and kimchi make great additions to a salad, and go well with peanut butter on toast!

What about fermented foods and FODMAPs?

Can you eat fermented food on a low FODMAP diet? Well, it’s a bit of a mixed bag. Monash's world-class FODMAP testing found that while some foods were low FODMAP eaten raw, fermenting them made them high FODMAP. For example, cabbage as a raw ingredient is low in FODMAPs in a 1 cup serving however when fermented to produce Sauerkraut this 1 cup of fermented cabbage is high in the polyol, mannitol. It’s best to check their app before you tuck into fermented foods.

Need help with the low FODMAP diet? Our FREE dietitian developed program will guide you through it, step-by-step. Includes a low FODMAP food guide. Sign up now.

If you are experiencing gut symptoms and have not been recommended a low FODMAP diet by a health professional, get started with the manage your gut symptoms program.

Reviewed by the healthylife Advisory Board March 2022