Is Sourdough Bread Acidic or Alkaline? The Truth Behind the Tang

January 8, 2026 •

3 min read

During fermentation, a key characteristic of traditional sourdough is a drop in pH, which means sourdough bread is acidic, not alkaline. This tangy quality is a result of the unique interaction between wild yeast and lactic acid bacteria, which produce acids that change the dough's chemistry.

Quick Summary

Sourdough bread is decidedly acidic due to lactic and acetic acid production during its slow fermentation process, not alkaline. This acidity contributes to its unique flavor, improves digestibility, and enhances its shelf life.

Key Points

Acidic, not Alkaline: Sourdough bread is acidic due to the lactic and acetic acids produced by bacteria during fermentation, with a typical pH of 3.5 to 5.5.
Source of Tang: The signature sour flavor comes from these naturally occurring acids, which are byproducts of the wild yeast and lactic acid bacteria present in the sourdough starter.
Digestibility Benefits: The long fermentation process breaks down phytic acid and fructans, making the bread's nutrients more bioavailable and easier for many people to digest compared to regular bread.
Controlling Acidity: Bakers can influence the final acidity and flavor by adjusting factors like fermentation temperature, the type of flour used, and the dough's hydration level.
Impact on Blood Sugar: The fermentation process results in a lower glycemic index for sourdough, which helps to slow the rate of sugar release into the bloodstream.
Not a Probiotic: While the starter culture contains live microorganisms, the baking process kills the bacteria. However, sourdough provides prebiotic fiber that nourishes good gut bacteria.

Sourdough: A Product of Acidic Fermentation

Traditional sourdough bread is acidic, with a typical pH range of 3.5 to 5.5. This tangy characteristic comes from the wild yeasts and lactic acid bacteria (LAB) in the sourdough starter. During fermentation, these microorganisms convert sugars in the flour into lactic and acetic acids, which lower the dough's pH. This acidic environment is key to both its flavor and health benefits.

The Role of Lactic and Acetic Acids

The balance of lactic and acetic acids determines sourdough's flavor. Lactic acid offers a milder, yogurt-like tang and is favored by warmer temperatures and higher hydration. Acetic acid, providing a sharper, vinegar-like sourness, is more volatile and prominent with cooler temperatures and stiffer doughs. Bakers adjust factors like temperature, hydration, and flour type to control the level of tanginess.

Acidity's Impact on Digestion and Nutrition

The long fermentation process makes sourdough potentially easier to digest and more nutritious than conventional bread.

Improved Mineral Absorption

Sourdough's acidity activates the enzyme phytase, which breaks down phytic acid found in grains. This enhances the absorption of minerals like zinc, iron, and calcium.

Enhanced Digestibility

For some, sourdough is easier on the stomach due to the breakdown of gluten proteins and fructans during fermentation. However, it is not gluten-free and is not suitable for those with celiac disease.

Better Blood Sugar Control

Sourdough bread generally has a lower glycemic index (GI), leading to a slower release of sugar into the bloodstream.

Sourdough vs. Regular Yeast Bread: A Comparison


Feature	Traditional Sourdough Bread	Commercial Yeast Bread
Leavening Agent	Wild yeast and LAB from starter.	Commercial baker's yeast.
Fermentation Time	Typically long (12-24+ hours).	Fast (a few hours).
Primary Acids	Lactic and acetic acids.	Carbonic acid, minimal organic acids.
Typical pH	3.5 to 5.5 (acidic).	5.0 to 6.5 (mildly acidic).
Shelf Life	Longer due to acids.	Shorter, often uses preservatives.
Flavor Profile	Distinctive tangy or sour flavor.	Milder, less complex.

Can Sourdough Fit into an Alkaline Diet?

Sourdough is acidic and doesn't fit the criteria of an alkaline food. The body tightly regulates blood pH, and diet has little effect on it. Sourdough's health benefits relate to its fermentation and prebiotic qualities, not its impact on overall pH balance. A balanced diet is key for health.

How Bakers Control Sourdough's Acidity

Bakers can adjust acidity through:

Temperature: Warmer temperatures favor acetic acid (sharper tang), cooler temperatures favor lactic acid (milder tang).
Flour: Whole grain and rye flours increase acidity.
Hydration: Stiffer doughs promote acetic acid, wetter doughs favor lactic acid.
Proofing Time: Longer fermentation enhances sourness.

Conclusion: The Final Verdict on Sourdough Acidity

Sourdough bread is acidic, a result of its natural fermentation. This acidity provides its complex flavor and health benefits like improved digestion and nutrient absorption. Instead of focusing on its intrinsic pH for an 'alkaline diet', consider the nutritional value and prebiotic effects of long-fermented sourdough. Understanding the science reveals the unique character of sourdough.

For more detailed information on the science of sourdough fermentation, you can explore research from the National Institutes of Health.(https://pmc.ncbi.nlm.nih.gov/articles/PMC7392915/)

Frequently Asked Questions

No, consuming sourdough bread does not make your body's pH more acidic. The body has sophisticated mechanisms to regulate blood pH within a very narrow, healthy range, and food has a negligible impact on it.

Yes, many people find sourdough bread easier to digest. The long fermentation process breaks down complex carbohydrates and some gluten, which can reduce bloating and digestive discomfort.

The typical pH of sourdough bread ranges from 3.5 to 5.5, which is notably acidic. This low pH helps inhibit the growth of spoilage microorganisms, extending its shelf life.

Sourdough bread is tangy because of the lactic acid and acetic acid produced by the lactic acid bacteria during the fermentation of the dough. The balance of these two acids determines the specific flavor profile.

No, baked sourdough bread does not contain live probiotics. The high heat of the baking process kills the beneficial bacteria. However, the fermentation process can create prebiotic fiber that nourishes good gut bacteria.

Yes, the type of flour used can affect the acidity. Whole grain and rye flours have more minerals, which can buffer the dough and encourage the production of acetic acid, leading to a tangier loaf.

Not always. Many commercial sourdoughs use some baker's yeast and additives to speed up production, which can result in a less complex flavor and lower acidity compared to traditionally, long-fermented homemade loaves.