What is the nutritional value of one slice of sourdough bread?

November 13, 2025 •

3 min read

According to the USDA, an average 50-gram slice of white sourdough contains approximately 130 calories, with its unique nutritional profile influenced by the long fermentation process. This makes knowing what is the nutritional value of one slice of sourdough bread essential for those monitoring their diet.

Quick Summary

This guide breaks down the typical macronutrient content of one slice of sourdough, including calories, protein, and carbohydrates. It also examines how fermentation enhances nutrient absorption and affects digestion, detailing key differences compared to standard bread varieties.

Key Points

Moderate Calories: One slice of sourdough bread typically contains between 130 and 188 calories, depending on its size and flour composition.
Enhanced Nutrient Absorption: The long fermentation process breaks down phytic acid, allowing the body to absorb minerals like iron, zinc, and magnesium more effectively.
Lower Glycemic Index: Fermentation results in a bread with a lower glycemic index, causing a more stable and gradual rise in blood sugar compared to standard breads.
Easier Digestion: Sourdough's pre-digestion of gluten and starches can make it easier to digest for individuals with mild gluten sensitivities or IBS.
Improved Nutritional Profile with Whole Grains: Choosing a whole grain sourdough loaf provides significantly more fiber, vitamins, and minerals than a white flour variety.

Sourdough's Unique Nutritional Breakdown

While sourdough's reputation for being a healthier bread option is well-known, understanding the specific nutritional value per slice provides more clarity for your diet. The exact figures can vary depending on the flour used (white versus whole grain), brand, and preparation method. However, general estimates can be derived from reliable sources like the USDA. A medium-sized slice, around 50-59 grams, offers a balance of macronutrients.

Macronutrients and Key Minerals in a Typical Slice

Calories: A single slice typically contains between 130 and 188 calories, depending on its size and density.
Carbohydrates: Expect around 25-37 grams of total carbohydrates. The fermentation process can alter the carb structure, contributing to sourdough's lower glycemic index.
Protein: A slice usually provides about 4-8 grams of protein, a decent amount that adds to its satiating quality.
Fat: Sourdough is naturally low in fat, with most slices containing only 1 gram or less.
Fiber: Fiber content varies based on the flour. White sourdough has about 1-2 grams per slice, while whole grain varieties offer significantly more.
Minerals: Sourdough's fermentation enhances the bioavailability of important minerals like iron, zinc, and magnesium.
Vitamins: The bread is often a source of B vitamins, including folate, thiamine, and niacin.

The Health Benefits of Fermentation

Sourdough's distinct advantages over standard bread are largely due to its unique, slow fermentation process, which utilizes a starter culture of wild yeast and lactic acid bacteria instead of commercial yeast. This process creates several health-boosting effects.

First, fermentation helps to break down phytic acid, an “anti-nutrient” naturally present in grains that can inhibit the absorption of minerals. By deactivating this compound, sourdough makes essential minerals like iron, zinc, and magnesium more available for the body to absorb.

Second, the breakdown of starches during fermentation results in a lower glycemic index (GI) compared to regular white bread. This means sourdough causes a slower, more gradual rise in blood sugar, making it a better option for those monitoring their glucose levels.

Finally, sourdough is often easier to digest. The fermentation process partially breaks down the gluten and FODMAPs (fermentable oligo-, di-, mono-saccharides, and polyols) in the flour, which can benefit individuals with mild gluten sensitivities or irritable bowel syndrome (IBS). While it is not gluten-free and not suitable for those with celiac disease, many find it gentler on their stomach.

Sourdough Nutrition: A Comparison Table

To put the nutritional value of one slice of sourdough bread into perspective, here is a comparison with other common bread types, based on approximate values for a 50-gram serving.


Nutrient	White Sourdough	Whole Wheat Sourdough	Standard White Bread	Standard Whole Wheat Bread
Calories	130-188 kcal	120-180 kcal	100-140 kcal	110-150 kcal
Carbohydrates	25-37 g	22-35 g	20-30 g	20-30 g
Fiber	1-2 g	3-5 g	1-2 g	2-4 g
Protein	4-8 g	5-9 g	3-6 g	4-7 g
Fat	<1 g	<2 g	<1 g	<2 g
GI Score	Lower	Lower	Higher	High/Variable
Mineral Bioavailability	Higher	Higher	Standard	Standard

Factors Affecting Sourdough's Nutritional Value

Several factors can influence the final nutritional profile of your sourdough loaf. The type of flour is one of the most significant. Whole grain flours, such as whole wheat or rye, contain more fiber, vitamins, and minerals than refined white flour. As the table above demonstrates, a whole grain sourdough will have a more robust nutritional profile than one made with white flour.

Another important factor is the length of the fermentation process. Longer fermentation times allow the wild yeast and bacteria more time to break down phytates and starches, maximizing the health benefits like improved mineral absorption and lower GI. Be aware that many commercially produced sourdoughs use added baker's yeast and a quicker process to speed production, which may reduce these benefits. For the most authentic, health-maximizing sourdough, consider seeking out an artisan bakery or learning to bake it yourself. Checking the ingredient list for a simple composition of flour, water, salt, and a starter culture is a good indicator of a traditional product.

Conclusion

While the exact nutritional values for one slice of sourdough bread can vary, it consistently offers a healthier alternative to conventional breads due to its unique fermentation process. The breakdown of antinutrients leads to enhanced mineral absorption, while a lower glycemic index and improved digestibility make it a smart choice for many people. To maximize these benefits, opt for whole grain varieties and seek out traditionally prepared loaves that have undergone a long fermentation. A systematic review on sourdough fermentation highlights its nutritional benefits.

Frequently Asked Questions

The calorie count for one slice of sourdough bread typically ranges from 130 to 188 calories, depending on the slice's thickness, size, and whether it's made from white or whole-grain flour.

Yes, whole grain sourdough is generally considered healthier. While both have the benefits of fermentation, the whole grains in whole wheat sourdough provide significantly more fiber and a richer variety of vitamins and minerals.

For many people, yes. The fermentation process breaks down some of the gluten and starches, reducing the amount of FODMAPs and potentially making it easier to digest, particularly for those with mild sensitivities.

Sourdough bread has a lower glycemic index than many other breads due to fermentation, which can lead to a slower rise in blood sugar. However, portion control and pairing it with protein or healthy fats are still important for managing blood sugar levels effectively.

While the sourdough starter contains beneficial bacteria (probiotics), the high temperatures used during the baking process kill most of them. The bread itself does contain prebiotics, which are fibers that feed the good bacteria already in your gut.

No, sourdough bread often has less gluten than conventional breads. The fermentation process helps to break down gluten proteins, making the bread more digestible for those with mild gluten sensitivities.

To ensure you are buying traditionally fermented sourdough, check the ingredient list. Look for a simple list of flour, water, salt, and a starter culture, and avoid loaves that also list commercial yeast.