Are Fermented Things Low in FODMAP? A Guide to Navigating Probiotics and IBS

According to Monash University research, fermenting foods can both increase and decrease FODMAP content, meaning not all fermented things are low in FODMAP. Understanding how fermentation impacts different foods is crucial for those following a low-FODMAP diet to manage irritable bowel syndrome (IBS) symptoms.

Quick Summary

Fermentation unpredictably alters a food's FODMAP content; some become low in FODMAPs, while others increase in FODMAPs like mannitol. Safe serving sizes are key, and checking reliable resources like the Monash University app is essential for confirming a fermented product's FODMAP status.

Key Points

• Fermentation Impacts FODMAPs Variably: The fermentation process can either decrease or increase the FODMAP content of a food, so testing is necessary to confirm its status.

• Portion Size is Critical: Even for low-FODMAP fermented foods like kombucha and sauerkraut, exceeding recommended serving sizes can lead to a high FODMAP load.

• Low FODMAP Options Exist: Tempeh, sourdough spelt bread, lactose-free yogurt, and small portions of red cabbage sauerkraut are safe choices.

• Traditional White Sauerkraut is High FODMAP: The fermentation of white cabbage increases the polyol mannitol, making it a high FODMAP food.

• Fermentation Reduces FODMAPs in Some Cases: The prolonged fermentation of sourdough and tempeh effectively breaks down fructans and GOS, making them more digestible.

• Read Labels and Use Apps: Commercial fermented products can contain high-FODMAP ingredients like garlic, onion, or added sugars, so checking labels and the Monash app is essential.

Understanding Fermentation and FODMAPs

Fermentation is an ancient process that uses microorganisms like bacteria and yeast to break down carbohydrates and other compounds in food. It’s widely celebrated for producing delicious flavors and providing potential health benefits through probiotics. However, the effect of fermentation on FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) is not straightforward. The final FODMAP content depends on the type of microbe used, the specific food, and the duration of fermentation.

For example, traditional sourdough bread undergoes a long fermentation process where wild yeast and lactic acid bacteria break down fructans, the FODMAPs in wheat. This process makes sourdough spelt bread low in FODMAPs, whereas non-fermented spelt products are high. Conversely, while raw white cabbage is low in FODMAPs, the fermentation into sauerkraut can increase its mannitol content, making it high in FODMAPs in larger servings. This unpredictable outcome means relying on reliable testing, such as from Monash University, is vital.

Low FODMAP Fermented Foods

Not all fermented foods are off-limits on a low-FODMAP diet. Many can be enjoyed in specific, tested portion sizes. Here are some examples of fermented foods that can be incorporated safely:

• Tempeh: Made from fermented soybeans, plain tempeh has been found to be low in FODMAPs at a serving size of 100g, as the fermentation process breaks down the GOS and fructans in soybeans.
• Red Cabbage Sauerkraut: Unlike its white cabbage counterpart, a half-cup serving of fermented red cabbage is low in FODMAPs, though a full cup may contain moderate amounts of fructans.
• Pickled Gherkins: Small servings of pickled gherkins (e.g., three pieces) are considered low FODMAP and can be a safe addition to your meals.
• Lactose-Free Yogurt: Cow's milk yogurt is typically high in lactose, but lactose-free versions are specifically treated with the lactase enzyme, making them a safe, probiotic-rich option.
• Miso Paste: A tablespoon of miso paste is low FODMAP, thanks to the fermentation process that breaks down the FODMAPs in the soybeans.
• Kombucha: Small servings of kombucha (up to 180ml or a small cup) have been tested as low FODMAP. However, larger servings increase fructan content, so portion control is key.

High FODMAP Fermented Foods to Limit

For those sensitive to FODMAPs, certain fermented products should be consumed with caution or avoided entirely, especially in the elimination phase:

• Traditional White Cabbage Sauerkraut: A higher serving of traditional sauerkraut can be high in the polyol mannitol, which can trigger symptoms.
• Regular Dairy Products: Many yogurts, kefir, and fresh cheeses contain significant lactose, a FODMAP that is not sufficiently broken down during standard fermentation to be considered low FODMAP. Lactose-free alternatives should be chosen instead.
• Large Servings of Kombucha: While small servings are safe, exceeding the recommended portion size for kombucha can significantly increase your intake of fructans.
• Silken Tofu: Unlike firm tofu, silken tofu is not pressed as heavily, meaning the water-soluble FODMAPs remain, keeping it high in FODMAPs.
• Some Pickled Vegetables: Some pickled items, such as cocktail onions, can be high in fructans or other FODMAPs and should be avoided. Always check the Monash app or label for specific ingredients like onion or garlic.

Comparison of Fermented Foods and Their FODMAP Content

Fermented Food	Raw Counterpart's FODMAP Status	Fermented FODMAP Status (Safe Serving)	Key FODMAP Type	Notes
Sourdough Spelt Bread	Spelt flour is high in fructans.	Low FODMAP (2 slices)	Fructans (reduced)	Long fermentation breaks down fructans.
Traditional White Cabbage Sauerkraut	Raw white cabbage is low FODMAP.	High FODMAP (at ½ cup)	Mannitol (increased)	Fermentation creates mannitol.
Tempeh	Soybeans are high in GOS and fructans.	Low FODMAP (100g)	GOS and Fructans (reduced)	Fermentation lowers FODMAP content.
Kombucha	Black/Green tea is low FODMAP.	Low FODMAP (180ml)	Fructans (increased)	Fructans increase with larger portions.
Lactose-Free Yogurt	Dairy yogurt is high in lactose.	Low FODMAP (standard serving)	Lactose (removed)	Enzyme is added to break down lactose.
Kimchi (made with Napa Cabbage)	Napa cabbage is low FODMAP.	Low FODMAP (⅓ cup)	Mannitol (increased in large portions)	Portion size is critical; often includes garlic/onion, which are high FODMAP.
Miso Paste	Soybeans are high in GOS and fructans.	Low FODMAP (1 tbsp)	GOS and Fructans (reduced)	Fermentation process lowers FODMAPs.

Making Your Own Fermented Foods

For those on a low-FODMAP diet, making your own fermented foods provides the highest level of control over ingredients and portion sizes. Here are some simple steps to ensure your homemade ferments are gut-friendly:

1. Choose Low-FODMAP Ingredients: Start with ingredients that are already low in FODMAPs, such as napa cabbage for kimchi or spelt flour for sourdough. Avoid high-FODMAP additions like onion and garlic.
2. Use Tested Recipes: Follow recipes specifically designed for a low-FODMAP diet, which often indicate longer fermentation times to ensure FODMAPs are properly broken down.
3. Monitor Fermentation Time: Longer fermentation can lead to a greater reduction in fructans and GOS, as bacteria have more time to consume these carbohydrates.
4. Practice Portion Control: Even with homemade ferments, portion sizes are crucial. Be mindful of the quantities you consume to stay within a safe limit.

How to Reintroduce Fermented Foods

Once you have completed the elimination and challenge phases of the low-FODMAP diet, you can begin reintroducing fermented foods to assess your tolerance. The process works as follows:

1. Start with Small Portions: Begin with a small, tested portion of a single fermented food, such as a tablespoon of red cabbage sauerkraut.
2. Monitor Symptoms: Observe your symptoms over a few days. If you experience discomfort, that particular food or portion size may be a trigger for you.
3. Increase Slowly: If the small portion is well-tolerated, gradually increase the serving size in subsequent tests to determine your personal threshold.
4. Repeat for Each Food: Test each fermented food individually to understand your unique tolerance to different FODMAP types. Some people might tolerate tempeh but not sauerkraut, for example.

Conclusion: Informed Choices Are Key

The question of are fermented things low in FODMAP is complex, with the answer being that it depends on the food, the fermentation process, and the portion size. While fermentation can reduce the FODMAP content of some foods, it can also increase it in others. The best approach is to rely on up-to-date, scientifically tested information from resources like the Monash University FODMAP app and to use portion control. By being mindful of your choices, you can enjoy the probiotic benefits of certain fermented foods while effectively managing your IBS symptoms.

Note: This article is for informational purposes and is not a substitute for professional medical advice. Always consult with a healthcare provider or a registered dietitian before making significant changes to your diet, especially if you have a medical condition like IBS. For more information on food processing and FODMAPs, visit the Monash University website, which provides comprehensive, test-based data: Monash University Blog on Fermented Foods and FODMAPs.

Frequently Asked Questions

Is all sauerkraut low FODMAP?

No, not all sauerkraut is low FODMAP. Traditional sauerkraut made from white cabbage is high in the polyol mannitol. However, red cabbage sauerkraut is low FODMAP in a ½ cup serving, but it's important to stick to that portion size.

Can I have kombucha on a low FODMAP diet?

Yes, you can have kombucha in small servings. A 180ml serving is considered low FODMAP, but larger portions increase the fructan content, so portion control is critical.

Why is traditional yogurt high FODMAP but some other fermented products are not?

Traditional yogurt is high in lactose, a FODMAP. While fermentation does reduce some lactose, it doesn't reduce it enough to be low FODMAP for most sensitive individuals. Lactose-free yogurts are treated with the lactase enzyme to break down the lactose, making them a better choice.

Is tempeh low FODMAP?

Yes, plain tempeh is low FODMAP. The fermentation of soybeans breaks down the FODMAPs (GOS and fructans) enough that a 100g serving is safe on the diet.

How do I know if a commercial fermented food is low FODMAP?

The best way is to check the Monash University FODMAP app, which tests specific foods and lists safe serving sizes. Additionally, read ingredient lists carefully to avoid high-FODMAP additions like onion, garlic, or certain sugars.

Does fermenting always lower the FODMAP content?

No, fermenting does not always lower the FODMAP content. The effect is unpredictable and depends on the food and process. As seen with sauerkraut, fermentation can sometimes increase the FODMAP content by converting sugars into polyols.

What is the difference between sauerkraut and kimchi in terms of FODMAPs?

Both can be high or low FODMAP depending on the ingredients and portion size. Traditional white cabbage sauerkraut is high FODMAP (mannitol), while red cabbage sauerkraut is low FODMAP in smaller servings. Kimchi made with napa cabbage is often low FODMAP in smaller portions (⅓ cup), but can contain high-FODMAP ingredients like garlic.