Introduction

For people living with irritable bowel syndrome (IBS) or other digestive sensitivities, bread often feels like a tricky food. Many conventional breads contain high levels of FODMAPs fermentable carbohydrates that can trigger bloating, gas, and discomfort. But what about sourdough? Is sourdough bread low FODMAP, and can it be enjoyed safely on a low FODMAP diet?

This guide will walk you through what makes sourdough different, how fermentation affects FODMAP content, and which varieties and portion sizes are suitable if you’re following a low FODMAP lifestyle.

Understanding the Low FODMAP Diet

The low FODMAP diet, developed by researchers at Monash University, limits certain carbohydrates that are poorly absorbed in the small intestine. These FODMAPs—such as fructans, lactose, polyols, and galactooligosaccharides—can ferment in the gut, leading to IBS symptoms.

The diet doesn’t remove all carbs; instead, it helps people identify which FODMAPs trigger their symptoms. Bread, especially those made from wheat, rye, or barley, is often restricted since these grains contain high levels of fructans.

What Makes Sourdough Bread Unique?

Sourdough bread is distinct because it’s made using a natural fermentation process involving wild yeasts and lactic acid bacteria. Unlike commercial breads that rely on quick-acting baker’s yeast, sourdough takes hours—or even days—to ferment.

This process not only develops flavor but also partially breaks down gluten and fructans, potentially making sourdough easier to digest for sensitive individuals.

Are All Types of Sourdough Bread Low FODMAP?

Not all sourdough breads are created equal. The flour used, fermentation time, and portion size all determine whether sourdough is low or high in FODMAPs.

Wheat-Based Sourdough Bread

• Potentially low FODMAP in small portions
• Long fermentation reduces fructans, but wheat still contains them
• Monash University testing shows about 1–2 slices (40g) may be tolerated

Spelt Sourdough Bread

• Often better tolerated than wheat-based sourdough
• Spelt flour contains fewer fructans and ferments more easily
• A good choice for people who want a traditional bread taste with lower FODMAP content

Rye Sourdough Bread

• Generally not suitable on a low FODMAP diet
• Rye flour is high in fructans even after fermentation
• Even small portions may trigger symptoms in IBS sufferers

How Fermentation Reduces FODMAPs

During fermentation, sourdough’s natural bacteria consume and break down fructans—a major FODMAP in wheat and rye. The longer the dough ferments, the greater the reduction in FODMAP content.

This doesn’t mean all FODMAPs are eliminated, but it explains why sourdough may be better tolerated than regular bread.

Portion Sizes: How Much Sourdough Is Safe on Low FODMAP?

According to Monash University’s testing:

• Wheat sourdough: ~40g (1 slice) is low FODMAP
• Spelt sourdough: ~2 slices may be tolerated
• Rye sourdough: remains high FODMAP, best avoided

It’s important to remember that tolerance varies from person to person. Start with a small portion and monitor symptoms.

Store-Bought vs. Homemade Sourdough

• Store-bought sourdough: Many commercial “sourdough” breads are not true sourdough. They may include added yeast and short fermentation, leaving more FODMAPs intact.
• Homemade or artisan sourdough: Typically undergoes long fermentation (12–48 hours), reducing FODMAP levels more effectively.

If you’re following a low FODMAP diet, look for sourdough with simple ingredients (flour, water, salt, starter) and long fermentation.

Nutritional Benefits of Sourdough

Beyond being easier on digestion, sourdough offers several health benefits:

• Rich in B vitamins, iron, and magnesium
• Prebiotic effects from fermentation that support gut bacteria
• Lower glycemic index compared to white bread, leading to steadier blood sugar levels
• More bioavailable minerals, since fermentation reduces antinutrients like phytic acid

Tips for Choosing Low FODMAP Sourdough

When shopping or baking, keep these guidelines in mind:

• Choose spelt or wheat sourdough with long fermentation
• Avoid sourdoughs that include added honey, high-FODMAP seeds, or sweeteners
• Look for loaves labeled as “long-fermented” or “traditional”
• When unsure, start with half a slice to test tolerance

How to Make Low FODMAP Sourdough at Home

Homemade sourdough gives you full control over fermentation and ingredients. Key tips include:

• Use spelt flour for a more IBS-friendly loaf
• Allow at least 12–24 hours of fermentation
• Stick to a simple recipe: flour, water, salt, sourdough starter

This approach maximizes the chances of achieving a lower-FODMAP bread.

Common Mistakes to Avoid

• Assuming all sourdough is low FODMAP — rye sourdough is not
• Eating too much at once — even low FODMAP foods can cause issues in large portions
• Buying supermarket “sourdough” without checking fermentation time or ingredients
• Confusing gluten-free with low FODMAP — they are not the same

Expert Insights on Sourdough and Gut Health

Research from Monash University and other digestive health studies shows that fermentation significantly lowers FODMAP content in bread. Dietitians often recommend spelt sourdough as the best tolerated option for those on a low FODMAP diet.

Still, they stress individual tolerance testing since IBS varies widely among people.

Low FODMAP Alternatives to Sourdough

If sourdough doesn’t work for you, there are other bread options:

• Gluten-free low FODMAP bread (rice, corn, oat-based)
• Oat bread (low FODMAP in moderation)
• Rice cakes or corn tortillas for lighter alternatives

FAQs on Sourdough and Low FODMAP

1. Can I eat sourdough on a low FODMAP diet?
Yes, in small portions, especially spelt or wheat sourdough. Rye sourdough is high FODMAP and should be avoided.

2. Is sourdough gluten-free?
No. Sourdough may be lower in gluten, but it is not gluten-free unless made with gluten-free flours.

3. How many slices of sourdough are safe?
Typically 1–2 slices, depending on flour type and your personal tolerance.

4. Why is spelt sourdough better for IBS?
Spelt has fewer fructans than wheat and ferments more easily, reducing FODMAPs further.

5. Does supermarket sourdough count as low FODMAP?
Not always. Many commercial sourdoughs are not true long-fermented breads and may still be high FODMAP.

6. Should I make sourdough at home for IBS?
Yes, homemade sourdough allows better control over fermentation and ingredients, making it more IBS-friendly.

Conclusion: Can Sourdough Fit in a Low FODMAP Diet?

So, is sourdough bread low FODMAP? The answer is yes—sometimes. Traditional, long-fermented wheat or spelt sourdough can be low FODMAP in small servings, while rye sourdough remains high FODMAP.

If you’re following a low FODMAP diet for IBS, sourdough can be a flavorful and nutritious option—just pay attention to flour type, fermentation process, and portion size. When in doubt, start small and monitor your body’s response.

Sources & Further Reading

• Monash University – FODMAP Diet Resources
• Harvard T.H. Chan School of Public Health – The Nutrition Source: Sourdough Bread