What is a Low Fodmap Serving of Sourdough Bread?

October 5, 2025 •

5 min read

According to Monash University, the institution that pioneered the low FODMAP diet, the long fermentation process used to make traditional sourdough bread significantly reduces its FODMAP content. This means that for many people with Irritable Bowel Syndrome (IBS), a specific quantity of sourdough can be a tolerable and delicious option, but understanding what is a low Fodmap serving of sourdough bread? is crucial for managing symptoms.

Quick Summary

Serving sizes for sourdough bread on a low FODMAP diet depend on the flour used and traditional fermentation methods. White wheat, whole wheat, and spelt sourdoughs are generally well-tolerated in two-slice servings due to fructan reduction during processing. Oat sourdough is more restricted, while others like rye are best avoided during the elimination phase.

Key Points

Fermentation Reduces FODMAPs: Traditional sourdough's long fermentation process significantly reduces the fructan content found in wheat flour, making it low FODMAP.
Serving Size is Key: A low FODMAP serving of white wheat, wholemeal wheat, and spelt sourdough is generally two slices.
Flour Type Matters: The type of flour used determines the serving size; for example, oat sourdough is limited to just one slice.
Avoid High FODMAP Flours: Sourdough made with flours like rye or kamut should be avoided during the elimination phase due to their high FODMAP content.
Look for Traditional Methods: When buying sourdough, check for a live starter or culture in the ingredients and opt for bread with a long fermentation process.
Certified Products are Safest: Choosing sourdough bread certified as low FODMAP by Monash University or FODMAP Friendly provides the highest assurance of safety.
Sourdough is NOT Gluten-Free: Although sourdough is lower in fructans, it still contains gluten and is not suitable for individuals with celiac disease.

Understanding the Low FODMAP Diet and Bread

The low FODMAP diet, developed by researchers at Monash University, is a dietary approach used to manage symptoms of Irritable Bowel Syndrome (IBS) and other functional gut disorders. FODMAPs are short-chain carbohydrates that can be poorly absorbed in the small intestine, leading to fermentation by gut bacteria and causing bloating, gas, pain, and other digestive distress. Many traditional wheat-based breads are typically high in fructans, a type of FODMAP, making them off-limits during the elimination phase of the diet.

However, sourdough bread offers a unique solution. Unlike commercially produced breads that use fast-acting yeast, traditional sourdough relies on a live culture of bacteria and wild yeast for fermentation. This lengthy process gives the microorganisms time to "eat" the fructans present in the flour, effectively lowering the overall FODMAP content of the final product. The result is a bread that many with IBS can tolerate, provided they adhere to specific, tested serving sizes. The key takeaway is that not all sourdoughs are created equal; the specific flour used and the duration of fermentation play a significant role in its FODMAP level.

Specific Low FODMAP Sourdough Serving Sizes

Monash University, the leading authority on FODMAPs, has tested various types of sourdough bread to determine safe serving sizes. The results show that the tolerable amount varies depending on the flour base. It is important to note that these portion sizes are specific to the elimination phase of the low FODMAP diet and should be used as a guide. Individuals can reintroduce higher quantities during the reintroduction phase to determine their personal tolerance.

White Wheat Sourdough

For white wheat sourdough, a low FODMAP serving is approximately 2 slices, or 109 grams. The long fermentation process breaks down the fructans in the wheat flour, making a two-slice portion acceptable for most individuals following the diet.

Wholemeal Wheat Sourdough

Similar to white wheat, wholemeal wheat sourdough is also typically low FODMAP in a two-slice serving. Monash University's testing indicates a safe portion size of 2 slices, or 97 grams. The wholemeal variety offers added fiber, which is often beneficial for gut health.

Spelt Sourdough

Made from spelt, an ancient grain with a lower natural fructan content than modern wheat, spelt sourdough is another excellent low FODMAP choice. A safe serving is typically 2 slices. It is essential to ensure the bread is made with 100% spelt flour, as mixed-flour products may have different FODMAP levels.

Oat Sourdough

Oat sourdough is a more nuanced case. It is considered low FODMAP at a smaller serving size of 1 slice, or 26 grams. A larger portion of 2 slices is considered moderate in FODMAPs (specifically GOS), so it is best to stick to the single-slice serving during the elimination phase.

Rye Sourdough

Rye is naturally very high in fructans, and while the sourdough process can reduce this amount, it is not considered low FODMAP. Rye sourdough should be avoided during the elimination phase and only tested during reintroduction with extreme caution.

How to Choose a Low FODMAP Sourdough

Simply seeing the word "sourdough" on a label is not a guarantee of a low FODMAP product. Several factors determine the final FODMAP content.

Read the Ingredients: A true sourdough is made with a live sourdough starter (or culture), flour, and water. Avoid products that list baker's yeast as a primary ingredient, as this suggests a quick fermentation process. While some certified low FODMAP sourdoughs might contain added yeast, relying on a product made with a traditional, live culture is the safest approach.
Check the Flour Type: Be mindful of other flours that may be included, such as rye or kamut, which are high in FODMAPs.
Verify with the Baker: If purchasing from a local bakery, inquire about their process. A traditionally made sourdough will have a longer fermentation or proving time, which is essential for breaking down the fructans.
Look for Certification: The easiest and most reliable option is to purchase sourdough bread that has been certified as low FODMAP by an organization like Monash University or the FODMAP Friendly Food Program.

Low FODMAP vs. High FODMAP Bread Comparison


Feature	Low FODMAP Sourdough Bread	High FODMAP Bread (e.g., regular wheat bread)
Fermentation Process	Long, slow fermentation using a live culture (starter).	Quick fermentation using fast-acting baker's yeast.
Fructan Content	Significantly reduced due to fermentation.	High, as the quick process does not break down fructans.
Serving Size	Generally two slices (dependent on flour).	Limited to a small portion (e.g., one slice for regular wheat) or best avoided.
Digestibility	Often easier to digest for those sensitive to fructans.	Can trigger significant digestive symptoms in sensitive individuals.
Flour Type	White wheat, wholemeal wheat, spelt, or other low FODMAP grains.	Modern wheat, rye, or other high FODMAP grains.

Incorporating Sourdough into a Low FODMAP Diet

For those who miss having bread, properly selected sourdough can be a welcome addition. Use the Monash University app or consult the guidelines outlined above to ensure you are selecting a low FODMAP-appropriate variety. Enjoy a two-slice portion with low FODMAP toppings such as a smear of butter, a drizzle of olive oil, or paired with a low FODMAP protein source. Remember to allow a few hours between servings to minimize the risk of cumulative FODMAP intake affecting symptoms. Listening to your body is also key, as individual tolerance levels can vary.

Conclusion

For individuals navigating a low FODMAP diet, understanding what is a low Fodmap serving of sourdough bread is key to enjoying this beloved food without triggering digestive discomfort. The long fermentation process of traditional sourdough breaks down problematic fructans, making specific types like white wheat, whole wheat, and spelt tolerable in two-slice servings. By prioritizing traditionally made or certified low FODMAP versions and being mindful of portion sizes, you can safely reintroduce this flavorful and versatile bread into your diet. Consulting a registered dietitian can provide further personalized guidance to help you find the right balance for your unique digestive needs. You can refer to the Monash University FODMAP blog for additional research on FODMAPs and sourdough.

Nutritional Breakdown and Health Considerations

Beyond just its FODMAP content, sourdough bread offers nutritional benefits, particularly if made from whole grains. It can be a good source of fiber, and the fermentation process may enhance the bioavailability of certain vitamins and minerals. The longer fermentation also results in a lower glycemic index compared to regular bread, meaning it has a gentler effect on blood sugar levels. It is important to emphasize that while sourdough reduces the FODMAPs in wheat, it is not a gluten-free product and is therefore unsuitable for those with celiac disease or a gluten intolerance.

For the best results, it's wise to source your sourdough from a reputable bakery that uses traditional methods or to purchase products explicitly labeled as low FODMAP. With careful attention to detail and portion control, sourdough bread can be a nourishing and delicious addition to a low FODMAP eating plan, proving that a restricted diet doesn't have to be restrictive in flavor.

Frequently Asked Questions

No, not all sourdough is low FODMAP. The bread must be made using a traditional, long fermentation process with a sourdough starter to ensure the fructans in the flour are sufficiently broken down. 'Sourdough style' loaves made with fast-acting yeast are not low FODMAP.

A safe low FODMAP serving of traditionally made white wheat sourdough bread is up to two slices, which is approximately 109 grams, according to Monash University.

The long fermentation process breaks down the fructans in the wholemeal wheat flour, making a two-slice serving (approx. 97 grams) low FODMAP. This allows for the benefits of whole grains while minimizing FODMAP content.

Yes, spelt sourdough is low FODMAP at a two-slice serving size, provided it is made using a traditional process with 100% spelt flour. Spelt is an ancient grain that has a naturally lower fructan content than modern wheat.

According to Monash University, a low FODMAP serving of oat sourdough is one slice (26 grams). The FODMAP levels (specifically GOS) increase in larger portions, so adherence to the smaller serving is advised during the elimination phase.

Look at the ingredient list for 'sourdough starter' or 'sourdough culture' and avoid loaves that primarily list fast-acting baker's yeast. If buying from a bakery, ask the baker about their process and fermentation time.

No, sourdough bread made from wheat or spelt flour is not gluten-free. It is only low FODMAP. It is not suitable for individuals with celiac disease or a gluten sensitivity, who must follow a completely gluten-free diet.