How much sourdough bread can you eat on a low FODMAP diet?

November 21, 2025 •

4 min read

According to Monash University, traditionally-made sourdough bread is lower in FODMAPs than regular bread due to its unique, long fermentation process. This means that for many people with Irritable Bowel Syndrome (IBS), it's possible to include a safe portion of sourdough bread on a low FODMAP diet by choosing the right type and quantity.

Quick Summary

The amount of sourdough bread safe for a low FODMAP diet depends on the flour used and how it's made. Traditional fermentation significantly reduces FODMAPs, making certain types, like white or wholemeal wheat and spelt sourdough, acceptable in specific portions. Not all sourdough is created equal, so checking ingredients and source is key.

Key Points

Serving Size Varies: The amount of sourdough you can eat depends on the flour used; always follow Monash University guidelines for specific serving sizes.
Fermentation is Key: Authentic sourdough fermentation, lasting 12+ hours, is what breaks down fructans and makes it lower in FODMAPs.
Choose the Right Flour: Stick to traditional wheat or spelt sourdough. Avoid rye, kamut, and other high-FODMAP flours.
Check for Traditional Methods: Many store-bought 'sourdough' breads are not traditionally made and can be high in FODMAPs. Look for a simple ingredient list without added baker's yeast.
Listen to Your Body: Individual tolerance varies. Start with a small serving during the elimination phase and monitor symptoms.
Consider Baking at Home: Homemade sourdough allows for full control over ingredients and the long fermentation process, ensuring it's low FODMAP.

The Science Behind Sourdough and FODMAPs

The key to why certain sourdough breads are low in FODMAPs lies in the traditional fermentation process. Unlike commercially produced breads that rely on fast-acting baker's yeast, authentic sourdough uses a live starter culture of wild yeasts and lactobacilli bacteria. This culture is responsible for a long, slow leavening and fermentation process, which can take 12 hours or more. During this time, the active microorganisms in the starter consume and break down the fermentable carbohydrates (FODMAPs), specifically fructans, which are abundant in wheat flour. By the time the bread is baked, the fructan content is significantly reduced, making it much more digestible for people with IBS and FODMAP sensitivities.

Recommended Sourdough Serving Sizes on a Low FODMAP Diet

The amount of sourdough you can safely eat is not a one-size-fits-all answer; it depends heavily on the flour used in its creation. Research from Monash University provides specific guidelines for different types of traditionally fermented sourdough. It is crucial to adhere to these tested serving sizes during the elimination phase of the low FODMAP diet to manage symptoms effectively.

White Wheat Sourdough: A low FODMAP serving is considered to be 2 slices, or approximately 109 grams. The long fermentation process breaks down enough fructans to make this amount tolerable for most people with IBS. Be sure to check that the bread was made using traditional methods.
Wholemeal Wheat Sourdough: For wholemeal varieties, the tested low FODMAP serving is also 2 slices, or around 97 grams. As with the white version, ensure it is authentically fermented to guarantee lower FODMAP content.
Spelt Sourdough: Traditionally made spelt sourdough is another excellent low FODMAP option, with a serving size of 2 slices, or about 52 grams. Spelt is an ancient grain naturally lower in fructans, which, when combined with the fermentation process, creates a very gut-friendly bread. Note that spelt flour is a close relative of wheat, so those with Celiac disease must avoid it.
Oat Sourdough: Monash testing shows that oat sourdough has a more moderate FODMAP level. The recommended low FODMAP serving is 1 slice (26g), with a second slice pushing it into moderate territory due to higher GOS content.
Rye and Kamut Sourdoughs: These varieties are typically high in fructans and GOS, and therefore should be avoided during the elimination phase of the low FODMAP diet, even with sourdough processing.

How to Choose a Low FODMAP Sourdough Bread

Not all bread labeled 'sourdough' is made using traditional, slow fermentation methods. Many supermarket varieties use added baker's yeast and a shorter rising time to speed up production, which does not sufficiently reduce the fructan levels. To find a truly low FODMAP product, consider these tips:

Check the ingredients list: Look for a short and simple list that includes only flour, water, salt, and a sourdough starter or culture. If baker's yeast is listed, it's likely not traditionally fermented.
Buy from a local baker: Artisanal bakeries often use traditional, long-fermentation methods. Don't be afraid to ask about their process and proving time.
Look for Monash certified products: Some brands have their products officially tested and certified as low FODMAP by Monash University. This is the most reliable way to ensure a product is safe.
Consider making your own: Baking sourdough at home gives you complete control over the ingredients and fermentation time, guaranteeing a low FODMAP end product.

Sourdough vs. Other Breads: A FODMAP Comparison


Bread Type	FODMAP Status	Why?	Recommended Serving Size (Monash University)
White Wheat Sourdough	Low	Long fermentation reduces fructans.	2 slices (~109g)
Regular White Bread	High (in larger quantities)	Quick fermentation leaves fructan levels high.	1 slice (~35g)
Spelt Sourdough	Low	Lower initial fructan content plus fermentation.	2 slices (~52g)
Regular Whole Wheat Bread	High (in larger quantities)	High fructan content in bran and germ.	1 slice (~24g)
Rye Sourdough	High	Rye flour is high in fructans and GOS.	Avoid during elimination phase

Conclusion

Sourdough bread does not have to be off-limits on a low FODMAP diet. By understanding the importance of traditional fermentation and adhering to specific serving sizes for different flour types, individuals with IBS can enjoy this tasty and often easier-to-digest bread. The key is to be a discerning consumer—check labels, ask bakers about their process, and stick to the Monash University-tested quantities. Whether you opt for a local bakery's traditionally-made loaf or bake your own, incorporating sourdough can add variety and enjoyment back into your diet without triggering uncomfortable symptoms.

Low FODMAP Sourdough Homemade Recipe

For those who prefer to have full control over their ingredients, a homemade spelt sourdough is a safe and delicious option. Use a spelt sourdough starter and ensure a long, slow fermentation process, which can be done by allowing the dough to rise for an extended period, perhaps overnight in the refrigerator. This cold fermentation further encourages the breakdown of FODMAPs, resulting in a perfectly digestible loaf. Experiment with different timings to find what works best for your tolerance and taste.

Authoritative Link Example: Monash University Low FODMAP App

Frequently Asked Questions

Sourdough bread is low FODMAP because of the long fermentation process used in its traditional preparation. During this time, the natural bacteria and yeasts in the sourdough starter break down the fructans (a type of FODMAP) found in the wheat flour. This reduces the overall FODMAP content of the finished bread.

The best way is to check the ingredient list. A traditional sourdough should only list flour, water, and salt, along with a 'sourdough starter' or 'sourdough culture'. If it lists added yeast or vinegar, it likely uses a shortcut process and is not a true, low FODMAP sourdough.

Yes, whole wheat sourdough that has been traditionally fermented is considered low FODMAP in a 2-slice serving, according to Monash University. The long fermentation reduces the fructans found in the bran and germ of the whole wheat grain.

For traditionally made spelt sourdough, a low FODMAP serving is 2 slices, or approximately 52 grams. Spelt flour is naturally lower in fructans, making it a good choice for those with sensitivities.

No, you don't have to avoid all sourdough. Certain types, particularly traditional wheat and spelt sourdough, are low FODMAP in specific serving sizes. However, you should avoid sourdough made from rye or kamut during this phase.

FODMAP stacking occurs when multiple low FODMAP foods, each containing a small amount of a specific FODMAP, are eaten together and combine to create a high FODMAP load. It's important to be mindful of this, even with sourdough. Stick to the recommended serving size per meal and leave a few hours between servings.

Freezing sourdough does not change its FODMAP content. However, baking your own large loaf and freezing pre-portioned slices can help with meal planning and ensure you always have a known low FODMAP bread on hand.