Can sourdough bread increase bowel movements?

October 20, 2025 •

4 min read

Studies show that certain types of bread, particularly whole grain sourdough, can aid bowel regularity. Can sourdough bread increase bowel movements? The science points to its unique fermentation process and enhanced prebiotic fiber, making it a potentially powerful tool for digestive wellness.

Quick Summary

Sourdough bread can support regular bowel movements, especially when made with whole grains. Its fermentation process makes prebiotic fibers more bioavailable and is gentler on the gut, fostering a balanced microbiome and improved motility.

Key Points

Fermentation Enhances Digestibility: The natural fermentation process of sourdough helps break down difficult-to-digest starches, gluten, and FODMAPs, making it gentler on the gut than standard bread.
Acts as a Prebiotic Source: Baked sourdough bread contains prebiotic fibers that nourish and support the growth of beneficial bacteria in your gut, leading to a healthier microbiome.
Promotes Regularity with Whole Grains: For the most significant effect on bowel movements, choose sourdough made with whole grains, which provide both soluble and insoluble fiber to add bulk and softness to stool.
Improves Nutrient Absorption: Sourdough's fermentation reduces phytic acid, an 'antinutrient' in flour, which allows for better absorption of key minerals like magnesium and iron.
Supports Balanced Gut Microbiome: The combined effect of prebiotics and enhanced fiber helps foster a more balanced gut flora, which is directly linked to improved bowel motility and reduced constipation.
Not All Sourdough is Equal: The digestive benefits are most pronounced in traditionally fermented sourdough. Be mindful of store-bought versions that use commercial yeast, as they may lack these advantages.

The Fermentation Factor: How Sourdough Aids Digestion

Sourdough bread is made through a slow, natural fermentation process using wild yeast and lactic acid bacteria (LAB) from a sourdough starter. This differs significantly from conventional bread, which relies on commercial yeast. The prolonged fermentation fundamentally alters the bread's composition, creating several digestive benefits that can lead to increased bowel movements for many individuals.

Fermentation and Nutrient Availability

One of the primary benefits of sourdough fermentation is its effect on the phytic acid present in grains. Phytic acid is an 'antinutrient' that binds to minerals, inhibiting their absorption in the gut. The lactic acid bacteria in sourdough break down this phytic acid, significantly improving the bioavailability of essential minerals like magnesium, iron, and zinc. This improved nutrient absorption is crucial for overall health and supports the proper functioning of the digestive system.

Creating Prebiotics for Gut Health

While the high heat of baking kills off the beneficial live bacteria (probiotics) in the sourdough starter, the bread still contains prebiotics. These are non-digestible fibers and carbohydrates that act as a food source for the beneficial bacteria already residing in your gut. By nourishing the gut microbiome, sourdough can help foster a more diverse and balanced gut environment, which is linked to better motility and reduced constipation. The prebiotic fiber is a key mechanism behind why sourdough bread can increase bowel movements.

The Impact of Whole Grains

The flour choice is critical for maximizing sourdough's effect on bowel movements. While white sourdough is easier to digest than regular white bread, wholegrain sourdough provides a significantly greater fiber content.

Insoluble Fiber: This fiber adds bulk to stool, helping it pass more easily through the intestines. Wholegrain flour is rich in insoluble fiber.
Soluble Fiber: This type of fiber absorbs water, forming a gel-like substance that softens stool and aids in regularity. The fermentation process in sourdough can enhance the functionality and bioavailability of these fibers.

Reduced FODMAPs for Sensitive Stomachs

Some individuals experience digestive issues like bloating and constipation due to high FODMAP content in foods, particularly fructans found in wheat. The long fermentation process in sourdough breaks down these FODMAPs, making the bread much gentler on the digestive system for many people with sensitive guts or Irritable Bowel Syndrome (IBS). A study reviewed in Nutrients highlighted that sourdough fermentation can significantly lower FODMAP levels in bread.

Sourdough vs. Regular Bread for Digestion

To understand why sourdough is often considered a superior choice for promoting bowel movements, it's helpful to compare it directly with commercially produced, non-sourdough bread.


Feature	Sourdough Bread	Regular Commercial Bread
Fermentation	Slow, natural process with wild yeast and LAB.	Rapid process using commercial baker's yeast.
Digestibility	Easier to digest due to breakdown of gluten and FODMAPs.	Can be harder to digest for some due to high gluten and FODMAP content.
Fiber Content	Highly dependent on flour; wholegrain versions offer superior fiber.	Varies widely; refined white bread is low in fiber.
Prebiotic Effect	Yes, contains prebiotic fibers that feed gut bacteria.	No significant prebiotic effect.
Mineral Absorption	Higher due to reduced phytic acid content.	Phytic acid can inhibit mineral absorption.
Gut Microbiome	Supports a balanced, diverse microbiome.	Can contain additives that may disrupt gut flora.

Maximizing the Benefits for Bowel Regularity

Simply eating sourdough won't be a magic cure for constipation. For the best results, you should consider these factors:

Choose Whole Grains: Always opt for wholegrain sourdough to get the most fiber. Check labels to ensure the bread is truly made with whole grains.
Ensure Traditional Fermentation: Be wary of supermarket bread labeled 'sourdough' that may use commercial yeast. True sourdough undergoes a long, slow fermentation, which is key to its benefits.
Stay Hydrated: Fiber needs water to do its job. Increase your fluid intake when adding high-fiber foods to your diet to prevent constipation.
Pair with Probiotics: For an added gut health boost, combine prebiotic sourdough with probiotic-rich foods like yogurt, kefir, or fermented vegetables.
Maintain a Balanced Diet: No single food can solve digestive issues. A diet rich in a variety of high-fiber foods, fruits, and vegetables is the best approach.

Conclusion: Sourdough Can Be a Key Ally for Bowel Health

For many, the answer to the question, can sourdough bread increase bowel movements?, is a qualified yes, especially when choosing wholegrain varieties. The unique fermentation process enhances digestibility, creates prebiotic fiber to nourish the gut microbiome, and, particularly in wholegrain versions, provides bulk-forming fiber. While not a cure-all, incorporating genuine, slow-fermented sourdough into a balanced diet can be a gentle and effective way to promote regularity and support overall digestive wellness. For more insights into gut health and fermented foods, consider exploring resources from reputable sources like the Mayo Clinic's Health System.

Frequently Asked Questions

No, the most effective sourdough for promoting bowel movements is made with whole grains, as this provides a much higher and more beneficial fiber content than sourdough made with refined white flour.

The slow fermentation process breaks down gluten proteins and reduces the content of FODMAPs, like fructans, making the bread easier to digest for many individuals, including those with mild gluten sensitivity.

While the sourdough starter contains live bacteria, the high temperatures of the baking process kill most of these off. The benefit comes from the prebiotic fiber that remains, which feeds your existing gut bacteria.

It is unlikely to cause constipation, especially if it's a wholegrain variety. However, like any high-fiber food, it must be consumed with adequate water intake. Without enough fluids, high fiber can contribute to constipation.

A moderate amount, such as one to two slices per day, is a good starting point. It should be part of a balanced diet rich in other fiber-rich foods, and intake should be increased gradually to avoid gas or bloating.

Artisan or homemade sourdough often undergoes a much longer, traditional fermentation. Many commercial 'sourdough' products use commercial yeast, which speeds up the process and reduces the gut-friendly benefits.

The long fermentation in genuine sourdough reduces the amount of fermentable carbohydrates (FODMAPs), particularly fructans, that can trigger symptoms in individuals with IBS.