Are Fermented Foods Allowed on a Low FODMAP Diet?

According to Monash University, the FODMAP content of foods can change with fermentation, meaning you can't assume a food is low FODMAP just because it's fermented. So, are fermented foods allowed on a low fodmap diet? The answer is a bit more complex than a simple yes or no.

Quick Summary

Many fermented foods are suitable for a low FODMAP diet when consumed in specific, tested portion sizes. Fermentation can decrease FODMAPs in some foods but increase them in others, so checking validated sources is essential.

Key Points

• Not all fermented foods are low FODMAP: Fermentation can both decrease and increase the FODMAP content of a food, so individual items must be checked.

• Portion control is key: Many fermented foods, like kimchi and kefir, are only low FODMAP in specific, small serving sizes.

• Trusted resources are vital: Always consult the Monash University FODMAP app for the most accurate and up-to-date serving size information.

• Fermentation can reduce FODMAPs in certain foods: For example, the process makes tempeh and genuine sourdough bread lower in FODMAPs than their base ingredients.

• Beware of hidden ingredients: Check labels on store-bought fermented products for high FODMAP additions like garlic, onion, and sweeteners.

• Listen to your body: Introduce new fermented foods in small amounts and monitor your body's response to determine your personal tolerance.

Understanding Fermentation and FODMAPs

Fermentation is an ancient process that uses bacteria and yeast to break down carbohydrates in food. This process can be both a friend and a foe to those on a low FODMAP diet. FODMAPs, or fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, are carbohydrates that are poorly absorbed in the small intestine. When they reach the large intestine, gut bacteria ferment them, producing gas and other byproducts that cause IBS symptoms like bloating and pain in sensitive individuals.

Interestingly, fermentation can sometimes decrease the FODMAP content of a food, making it more tolerable. For instance, the bacteria in sourdough bread and tempeh break down the fructans and galacto-oligosaccharides (GOS) respectively, lowering the overall FODMAP content. However, this isn't a universal rule. In some cases, the fermentation process can actually increase the FODMAP levels, as seen with some types of sauerkraut. This is why testing individual foods is crucial.

Low FODMAP Fermented Foods and Portion Sizes

For those following a low FODMAP diet, specific fermented foods can be enjoyed in controlled portions. The key is to rely on trusted sources like Monash University, which rigorously tests foods for their FODMAP content. Always remember to check labels for added high FODMAP ingredients, such as garlic, onion, or high-fructose corn syrup, especially in store-bought products.

Fermented dairy

• Lactose-free Yogurt and Kefir: Lactose-free varieties are safe. One tablespoon of traditional kefir or a 125g tub of coconut yogurt is considered low FODMAP.

Fermented vegetables

• Kimchi: Made from napa cabbage and other vegetables, a serving of up to ½ cup (47g) is low FODMAP. It's important to choose versions without added garlic or onion.
• Red Cabbage Sauerkraut: A portion of ½ cup is low FODMAP, but larger amounts increase fructans.
• Pickled Gherkins: Three pickled gherkins are a low FODMAP serving.

Fermented soy products

• Tempeh: Made from fermented soybeans, a slice (100g) is a low FODMAP serving and an excellent source of protein.
• Miso Paste: A tablespoon of this fermented soybean paste is low FODMAP and adds great flavor to soups and dressings.
• Firm Tofu: While not heavily fermented, the pressing process removes FODMAPs, making a 1-cup serving low FODMAP.

Fermented drinks and grains

• Kombucha: This fermented tea can be enjoyed in a small cup (180ml) as a low FODMAP serving. Some brands may add high FODMAP fruits, so check the label.
• Sourdough Bread: True sourdough, made with a long fermentation process, is lower in fructans. Two slices (52g) of spelt sourdough bread are a low FODMAP portion. Be sure the ingredients list does not include commercial yeast or vinegar.

High FODMAP Fermented Foods to Limit or Avoid

Just as some fermentation can be beneficial, other fermented foods remain high in FODMAPs, even in small amounts. These should be avoided during the elimination phase of the diet to prevent symptoms.

• White Cabbage Sauerkraut: Unlike red cabbage sauerkraut, which can be low FODMAP in smaller servings, common white cabbage sauerkraut becomes high in the polyol mannitol when fermented. A 1-cup serving is high FODMAP.
• Silken Tofu: Because the water is not pressed out during processing, silken tofu retains the high FODMAP content of the original soybeans.
• Fermented Vegetables with High FODMAP Additives: Pickles or other fermented vegetable mixes containing ingredients like garlic, onion, or cocktail onions should be avoided.

Low FODMAP vs. High FODMAP Fermented Foods

Feature	Low FODMAP Options	High FODMAP Options (Standard Servings)
Portion Size	Small, tested amounts (e.g., ½ cup kimchi, 1 slice tempeh)	Often high in FODMAPs even in small amounts (e.g., silken tofu)
Underlying Food	Foods where fermentation reduces FODMAPs (e.g., tempeh, sourdough)	Foods where fermentation increases or does not reduce FODMAPs (e.g., white cabbage sauerkraut)
Common Examples	Lactose-free yogurt, tempeh, kombucha, kimchi, sourdough spelt bread	White cabbage sauerkraut, silken tofu, most garlic-infused condiments
Preparation Details	Made from naturally low FODMAP bases or processed to reduce FODMAPs	Contains high FODMAP ingredients before fermentation or the process increases FODMAPs
Guideline	Adhere strictly to Monash app serving sizes	Avoid during the elimination phase

Tips for Incorporating Fermented Foods

1. Start Slow: If you are new to fermented foods, begin with very small portions. A tablespoon of kefir or a small amount of kimchi is a good starting point.
2. Monitor Your Symptoms: Track your symptoms after consuming new foods. This helps you identify your personal tolerance levels. Keep a food diary to note portions and reactions.
3. Use the Monash App: The official Monash University FODMAP app is an essential tool for accurate, up-to-date information on serving sizes.
4. DIY with Caution: When making fermented foods at home, be mindful of ingredients. For example, a low FODMAP kimchi recipe should omit garlic and high FODMAP chili.
5. Choose Plain Options: Opt for plain, unflavored fermented products to avoid hidden high FODMAP sweeteners or flavorings.
6. Work with a Dietitian: A registered dietitian specializing in IBS can provide personalized guidance and help you navigate the reintroduction phase of the low FODMAP diet.

Conclusion

In conclusion, fermented foods are not automatically off-limits on a low FODMAP diet. The key lies in understanding that fermentation affects different foods in unique ways. While some foods like tempeh and real sourdough become more digestible, others like white cabbage sauerkraut can become problematic in larger portions. By paying close attention to portion sizes and relying on certified resources like the Monash University FODMAP app, individuals can safely incorporate many nutritious fermented foods into their diet without triggering uncomfortable IBS symptoms. The goal of a low FODMAP diet is not permanent restriction but to discover personal triggers and build a broad, symptom-free diet, which for many can include these beneficial foods.

For more research-backed information on the low FODMAP diet, visit the official Monash University FODMAP website.

Frequently Asked Questions

Does fermentation always make a food low FODMAP?

No, fermentation does not always make a food low FODMAP. In some cases, like with common white cabbage sauerkraut, the fermentation process can increase the FODMAP content, making it high FODMAP even in standard servings.

Which fermented foods are safe on a low FODMAP diet?

Safe options include lactose-free yogurt, plain tempeh, genuine sourdough spelt bread, red cabbage sauerkraut in small servings, and specific portions of kimchi and kombucha. Always check the Monash app for serving sizes.

Can I eat sauerkraut on a low FODMAP diet?

It depends on the cabbage used. Red cabbage sauerkraut is low FODMAP in a ½ cup serving, but white cabbage sauerkraut is high in the polyol mannitol in a standard serving.

Why are some soy products low FODMAP while others aren't?

The key lies in how they are processed. Firm, drained tofu is low FODMAP because water is pressed out, taking some FODMAPs with it. Fermented tempeh also has reduced FODMAP content. However, silken tofu is not drained and is high FODMAP.

Is kombucha allowed on a low FODMAP diet?

Yes, a small cup (180ml) of kombucha is considered low FODMAP. Check labels to ensure no high FODMAP ingredients like certain fruits or added sugars were used in flavoring.

How should I introduce fermented foods while on a low FODMAP diet?

Start with a very small portion, like a tablespoon, and consume it alongside other low FODMAP foods. Gradually increase the serving size over time, paying close attention to any symptoms.

Where can I find reliable information on FODMAP content?

The most reliable source for FODMAP information is the official Monash University FODMAP app. It contains the most up-to-date and thoroughly tested data.