Can I Eat Sourdough Bread If I Have SIBO? A Gut-Friendly Guide

October 16, 2025 •

4 min read

According to researchers at Monash University, the long, slow fermentation process of traditional sourdough can significantly reduce its FODMAP content, making it more digestible than regular bread for many people with sensitivities. While sourdough is often an approved food on a low-FODMAP diet, which is frequently used to manage SIBO, success depends on the bread's ingredients and preparation, as well as individual tolerance.

Quick Summary

Individuals with Small Intestinal Bacterial Overgrowth (SIBO) often tolerate traditional, long-fermented sourdough better than other breads. The fermentation breaks down fructans, a fermentable carbohydrate, reducing the potential for digestive distress. Selecting genuine sourdough made with low-FODMAP flours and monitoring portion sizes are key strategies.

Key Points

Sourdough fermentation reduces FODMAPs: The long, natural fermentation process of traditional sourdough significantly lowers fructan content, making it easier to digest for many people with SIBO.
Choose wisely, avoid 'sourfaux': Commercial sourdough often uses commercial yeast and shortcuts, lacking the long fermentation needed to reduce FODMAPs. Look for simple ingredients and a long proofing time.
Tolerance is individual: What works for one person with SIBO may not for another. Portion size and personal sensitivity play a big role in tolerating sourdough.
Sourdough is not gluten-free: The fermentation process reduces but does not eliminate gluten, so sourdough is unsafe for individuals with celiac disease.
Consider flour types: Wheat or spelt sourdough are often tolerated, while rye sourdough is typically high in FODMAPs. Gluten-free sourdough options are also available.

Understanding SIBO and Its Dietary Triggers

Small Intestinal Bacterial Overgrowth (SIBO) is a condition where an excessive amount of bacteria, especially the wrong type, grows in the small intestine. While a healthy gut relies on a balanced microbial community, this overgrowth leads to uncomfortable symptoms such as bloating, abdominal pain, gas, and altered bowel movements. A key dietary strategy for managing SIBO is the low-FODMAP diet.

FODMAPs are a group of short-chain 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 trigger SIBO symptoms. A low-FODMAP diet temporarily restricts these fermentable carbohydrates to starve the overgrown bacteria and alleviate symptoms. Wheat-based products are often restricted on this diet because they are a primary source of fructans, a type of FODMAP. This is where sourdough bread presents a unique opportunity.

The Sourdough Advantage: How Fermentation Reduces FODMAPs

Traditional sourdough bread is made using a starter culture of wild yeasts and lactic acid bacteria instead of commercial baker's yeast. This slow, natural fermentation process is what sets it apart. During fermentation, the microorganisms in the starter feed on the carbohydrates present in the flour, including the fructans. This "pre-digestion" significantly lowers the FODMAP content of the final product, potentially making it easier for people with SIBO to tolerate.

Benefits of traditional sourdough fermentation:

Fructan Reduction: The microbes actively consume and break down fructans during the long fermentation period, which can last 12 to 24 hours or more.
Increased Digestibility: The pre-digestion of complex carbohydrates and some proteins makes the bread gentler on the gut.
Improved Nutrient Availability: Fermentation can break down phytic acid, an "anti-nutrient" in grains that can inhibit mineral absorption, thereby increasing the bioavailability of minerals like zinc and magnesium.
Lower Glycemic Index: Sourdough has been shown to have a lower glycemic index compared to conventional bread, resulting in a slower and more gradual release of sugar into the bloodstream.

Not All Sourdough Is Equal: Choosing Wisely

While the science behind traditional sourdough and FODMAP reduction is promising, it's crucial to understand that not all loaves labeled "sourdough" are the same. Many commercial breads use a combination of sourdough starter and commercial yeast to speed up the process, or use flavoring additives like vinegar to mimic the tangy taste. This accelerated production bypasses the extensive fermentation needed to break down FODMAPs effectively. To ensure you are getting a genuine, gut-friendly loaf, read the ingredient list carefully.

Comparing Traditional vs. Commercial Sourdough


Feature	Traditional Sourdough	Commercial "Sourdough"
Fermentation	Slow and long (often 12-24+ hours)	Short and fast (2-4 hours)
Leavening Agent	Naturally occurring wild yeasts and bacteria from the starter	Commercial baker's yeast
FODMAP Content	Significantly reduced fructan levels	High fructan levels, similar to regular bread
Ingredients	Typically flour, water, salt, and a starter	May contain commercial yeast, vinegar, and other additives
Flour Type	Can be made with low-FODMAP wheat or spelt; some wholemeal options also tolerate well	Often made with high-FODMAP wheat and other ingredients
Digestibility	Easier to digest for many individuals	Can cause symptoms like bloating and gas

Considering Flour Type for SIBO

For those with SIBO, the type of flour used in the sourdough is also a significant factor. While traditional wheat and spelt sourdoughs are often tolerated, not all flours are suitable. For example, rye sourdough is typically high in FODMAPs and should be avoided. For those with gluten sensitivity, gluten-free sourdough options made with low-FODMAP flours like rice, millet, or quinoa are also available. It is important to note that while fermentation reduces fructans, it does not eliminate gluten, and sourdough is not safe for individuals with celiac disease.

How to Safely Reintroduce Sourdough into Your Diet

If you have SIBO, it is recommended to test your tolerance for sourdough in the reintroduction phase of the low-FODMAP diet, ideally under the guidance of a healthcare provider or a dietitian experienced with SIBO.

Steps for reintroduction:

Start Small: Begin with a small portion, such as one slice of a certified low-FODMAP or genuinely traditional wheat or spelt sourdough.
Monitor Symptoms: Track your symptoms for a few days before trying the next portion. Note any bloating, gas, or pain.
Increase Gradually: If you tolerate the small portion well, gradually increase the amount over several days to find your personal tolerance level.
Confirm Authenticity: When purchasing bread, check the ingredient list for commercial yeast. If possible, buy from a local baker who can confirm a long fermentation process, or choose a product certified by Monash University as low-FODMAP.

Other SIBO-Friendly Bread Alternatives

If sourdough isn't a good fit, or you need other options, there are several alternatives that are generally well-tolerated on a SIBO diet.

Gluten-Free Bread: Some gluten-free breads made from low-FODMAP flours like rice, millet, or quinoa can be safe. However, always check the ingredients, as some contain high-FODMAP additives like inulin.
Grain-Free Bread: Made from flours like almond or coconut, these can be a good option for those sensitive to grains.
White Bread: Some low-fermentation diets approve of small, infrequent servings of simple white bread, as it contains fewer fermentable components compared to whole wheat, but this should be tested individually.

Conclusion

For many individuals with SIBO, traditional, long-fermented sourdough bread can be a safe and enjoyable option that doesn't trigger uncomfortable digestive symptoms. The key lies in the extensive fermentation process, which naturally reduces the bread's FODMAP content. However, not all sourdough is created equal, and choosing genuinely fermented bread made with tolerated flours is essential. When reintroducing sourdough, start with small portions and carefully monitor your body's reaction. By being a mindful consumer and working with a healthcare professional, you can navigate your diet and enjoy a satisfying bread option without compromising your gut health.

For further guidance on the low-FODMAP diet and SIBO management, consider consulting authoritative resources such as Monash University.

Frequently Asked Questions

The main reason is the long fermentation process used in traditional sourdough. This process allows the wild yeasts and lactic acid bacteria to break down fructans, which are fermentable carbohydrates that often trigger SIBO symptoms, making the bread easier to digest.

Check the ingredient list. True sourdough should contain only flour, water, salt, and a starter culture, with no added commercial yeast. A longer fermentation process (12-24+ hours) is key, so look for artisan-made loaves or products specifically certified by Monash University.

No, sourdough fermentation does not eliminate gluten. It is only suitable for individuals with an intolerance to the FODMAPs in wheat, not for those with celiac disease or a genuine gluten allergy.

Yes. While white wheat and spelt sourdoughs are often tolerated in small portions, wholemeal wheat sourdough can be higher in FODMAPs. Rye sourdough is typically high in FODMAPs, and gluten-free sourdoughs made with low-FODMAP flours like rice or millet are also available.

Tolerance varies by individual, but a good starting point is one slice of traditional, long-fermented sourdough. It's best to test your personal tolerance by gradually increasing the portion size while monitoring your symptoms.

Generally, sourdough should be introduced during the reintroduction phase of a low-FODMAP diet, not the initial elimination phase. This helps to determine your specific tolerance once symptoms have subsided.

Other safe options include white bread in small amounts, certified low-FODMAP gluten-free breads made from flours like rice or millet, and grain-free breads from almond or coconut flour. These should also be tested for individual tolerance.