Are Fermented Foods OK on a Low FODMAP Diet? The Definitive Guide

January 4, 2026 •

4 min read

According to Monash University, the originators of the low FODMAP diet, some fermented foods are indeed safe to eat while others are not. The key lies in understanding how the fermentation process alters the FODMAP content of the final product and how serving sizes impact tolerance.

Quick Summary

Some fermented foods can be included in a low FODMAP diet, depending on the food type, fermentation process, and serving size. Key factors include the breakdown of FODMAPs like lactose and fructans by bacteria and yeast during fermentation. Certain options like red cabbage sauerkraut and specific yogurts can be tolerated, while others like white cabbage sauerkraut and some kefirs may be high in FODMAPs.

Key Points

Fermentation alters FODMAP content: Live bacteria and yeast break down fermentable carbohydrates during the fermentation process, which can lower the final FODMAP levels.
Not all fermented foods are low FODMAP: Foods made with naturally high-FODMAP ingredients, like white cabbage sauerkraut or some kefirs, can remain high in FODMAPs, particularly in larger servings.
Serving size is crucial: Monash University guidelines specify portion sizes for many fermented foods. A small, 'green-light' serving may be fine, but a larger one could trigger symptoms.
Look for specific types: Red cabbage sauerkraut, long-fermented sourdough bread, and tempeh are generally safe low-FODMAP options.
Individual tolerance varies: Use the reintroduction phase of the low FODMAP diet to test your personal tolerance to fermented foods. Start with small quantities and monitor symptoms carefully.
Check for hidden high-FODMAP ingredients: Always read labels on store-bought fermented foods for additives like garlic, onion, inulin, or high-fructose corn syrup.

The Fermentation Paradox: Why Some Foods Are OK and Others Aren't

The relationship between fermented foods and the low FODMAP diet can be confusing. Fermented foods are often celebrated for their probiotic benefits and gut-supporting properties, which seems beneficial for those with Irritable Bowel Syndrome (IBS). However, many fermented foods are made from ingredients that are naturally high in FODMAPs. The fermentation process is what makes the difference. During fermentation, the live microorganisms, such as bacteria and yeasts, consume the fermentable carbohydrates (FODMAPs) in the food. The longer the fermentation process, the more FODMAPs are broken down, potentially lowering the final content to a tolerable level.

Lactose Fermentation in Dairy Products

Dairy products are a prime example. Regular milk is high in lactose, a type of FODMAP. In the production of cheese, bacteria ferment the milk, breaking down the lactose. This is why aged, hard cheeses like cheddar and parmesan are low FODMAP, whereas fresh cheeses like ricotta or cottage cheese contain more lactose and are often not tolerated. Similarly, some yogurts and kefir can be low FODMAP if fermented for a long time or if lactase enzymes are added to break down the lactose. It is crucial to check product labels for added high-FODMAP ingredients like high-fructose corn syrup or inulin.

Cabbage Fermentation in Sauerkraut and Kimchi

Another example is fermented cabbage. Traditional sauerkraut made from white cabbage is actually high in mannitol, another type of FODMAP, because the fermentation process converts some of the naturally occurring fructose into mannitol. However, red cabbage sauerkraut is considered low FODMAP in servings up to 1/2 cup, and homemade versions can be carefully controlled for FODMAP content. The same logic applies to kimchi. When made with low FODMAP ingredients like Napa cabbage, daikon, and the green parts of scallions, and without high FODMAP additions like garlic or onion, kimchi can be safe in controlled portions.

Fermented Foods on a Low FODMAP Diet: What to Enjoy

Incorporating low-FODMAP fermented foods can be beneficial for gut health without triggering symptoms. Here is a list of generally safe options and important considerations:

Certain Yogurts: Look for plain, unsweetened lactose-free yogurt or those specifically tested and certified as low FODMAP. Coconut yogurt can also be a safe alternative, provided it contains active cultures and no high FODMAP additives.
Red Cabbage Sauerkraut: A serving of 1/2 cup or less is generally well-tolerated. Always check for added ingredients that might be high in FODMAPs, such as garlic or onion.
Sourdough Bread: The long fermentation process of sourdough helps break down fructans, the FODMAP in wheat. True, traditionally fermented spelt or wheat sourdough can be low FODMAP. It's essential to ensure the bread was made using a genuine sourdough process.
Tempeh: This fermented soybean product is low FODMAP in servings of about 1/2 cup. Tempeh is a high-protein option that works well in stir-fries and other dishes.

Comparison Table: Fermented Foods and FODMAP Status


Fermented Food	FODMAP Status (Guideline)	Key Considerations
Milk Kefir	Low to Moderate FODMAP	Can be low in lactose if fermented longer; limit to 1-3 tablespoons.
Water Kefir	Low FODMAP	Dairy-free, but individual tolerance may vary. Start with small amounts.
Red Cabbage Sauerkraut	Low FODMAP	Safe in 1/2 cup servings. Avoid varieties with garlic or onion.
White Cabbage Sauerkraut	High FODMAP	Avoid, as fermentation creates mannitol.
Sourdough Bread	Low FODMAP	Choose true, long-fermented varieties; testing for gluten-free grains can provide extra assurance.
Aged Cheese (e.g., Cheddar, Parmesan)	Low FODMAP	Lactose is broken down during aging; fresh cheeses are higher FODMAP.
Tempeh	Low FODMAP	Fermented soybeans are well-tolerated in moderate servings.
Lactose-Free Yogurt	Low FODMAP	Ensure no high-FODMAP additives. Check for active, live cultures.

Importance of Individual Tolerance and Portion Sizes

While Monash University provides valuable guidance, individual tolerance is key. The low FODMAP diet involves an elimination phase followed by a reintroduction phase to determine which FODMAPs trigger symptoms. It is during this reintroduction phase that you can test your personal tolerance to various fermented foods. Always start with a small serving and monitor your body's reaction. What works for one person may not work for another. It's also vital to remember that 'moderate' amounts of some foods are acceptable on the low FODMAP diet, but exceeding the recommended portion size can lead to symptoms.

Conclusion: Navigating Fermented Foods on a Low FODMAP Diet

The short answer to whether fermented foods are okay on a low FODMAP diet is: sometimes, and with caution. The crucial factors are the type of food, the method of fermentation, and the serving size. By choosing options like red cabbage sauerkraut, true sourdough bread, tempeh, and lactose-free dairy alternatives, you can enjoy the benefits of fermented foods while minimizing the risk of triggering IBS symptoms. Always refer to a trusted source like the Monash University FODMAP app and consider working with a registered dietitian to navigate the reintroduction phase effectively. The right approach allows for dietary diversity and improved gut health, even with FODMAP sensitivities.

For more detailed information on specific ingredients and food testing, the Monash University Low FODMAP Diet app is an indispensable resource. It provides up-to-date guidance based on laboratory analysis, making it the gold standard for anyone following this dietary protocol.

Frequently Asked Questions

The difference depends on the type of cabbage used. Red cabbage sauerkraut is generally low FODMAP in a 1/2 cup serving. Traditional sauerkraut made from white cabbage is high in mannitol, a type of FODMAP created during fermentation, and is not recommended.

While water kefir is low FODMAP, the FODMAP content of kombucha can vary depending on the type of tea, sugar, and fermentation time. It is best to approach kombucha with caution and test your own tolerance, as there is no universal FODMAP-tested serving size available.

Not necessarily. A small serving of milk kefir (around 1-3 tablespoons) can be moderate to low in FODMAPs due to the bacteria breaking down the lactose during fermentation. Water kefir is typically a safer, dairy-free option that is low FODMAP. Be sure to check labels for added high-FODMAP flavorings.

Yes, true sourdough bread, especially from spelt flour, can be low FODMAP because the long fermentation process breaks down the fructans. For best results, ensure the bread was made using a traditional, long-fermentation method.

Probiotics are live bacteria found in fermented foods, while prebiotics are fibers that feed beneficial gut bacteria. Many high-FODMAP foods are prebiotics. For those with IBS, adding probiotics from fermented foods is possible with careful selection, but caution is needed with prebiotics to avoid triggering symptoms.

Lactose-free yogurt is not automatically low FODMAP. You must also check for other high-FODMAP additives like inulin, high-fructose corn syrup, or certain fruits. Certified low-FODMAP or plain coconut yogurt with active cultures can be good alternatives.

It is generally recommended to avoid introducing new variables, like fermented foods, during the strict elimination phase. The reintroduction phase is the appropriate time to test your tolerance for specific low-FODMAP fermented foods in controlled amounts.