Sourdough is a type of bread first made in Ancient Egypt over 5,000 years ago. It’s considered the earliest form of leavened bread, or bread made with a rising agent.
Until the development of commercial yeasts in the 1800s, sourdough, made with naturally occurring yeasts and lactic acid bacteria, was the main type of leavened bread consumed worldwide.
Sourdough undergoes natural fermentation, which may lessen its impact on blood sugar, improve its digestibility, and enhance nutrient bioavailability.
Here’s everything you need to know about sourdough bread, including its potential health benefits, nutrition, and uses.
A Better Choice for Blood Sugar Control
Compared to regular leavened bread, sourdough has been shown to have less of an impact on blood sugar levels and is lower on the glycemic index than other types of bread, like white bread. The glycemic index (GI) is a classification system that ranks carbohydrate-rich foods on a scale of 0-100 according to their impact on blood sugar levels. Low-GI foods score less than 55, moderate GI foods score between 56-69, and high-GI foods score greater than 70 or greater. The GI estimates how quickly food is digested and absorbed into the bloodstream.
The fermentation process used to make sourdough produces organic acids, such as lactic acid and acetic acid, that slow the absorption of starch in the digestive tract, which results in a slower rise in blood sugar.
Studies show that sourdough bread has a lower GI than bread made with baker’s yeast. For example, the GI for a 30-gram (g) serving of bread made with white wheat flour is 71, which is considered high GI, while the GI for a 30g serving of sourdough bread is 54, which is considered low GI. This means that sourdough may be a better choice for promoting healthy blood sugar regulation compared to bread made with baker’s yeast.
A 2023 study that included 43 women with gestational diabetes and 38 pregnant women without diabetes found that after consuming refined white bread, the women experienced 45.5% greater insulin secretion and 9.6% higher post-meal blood sugar levels compared to when the women consumed the same amount of whole grain sourdough bread.
A 2022 review of 18 studies concluded that sourdough bread, especially sourdough made with whole wheat flour, has a lower impact on blood sugar levels than other types of bread, such as refined white bread.
This suggests that swapping more common types of bread, like white sandwich bread, with sourdough may help support healthier blood sugar control.
May be Easier to Digest
Many people report that sourdough is easier to digest than commercially-leavened breads. This is due to the fermentation process that sourdough undergoes, which improves its protein digestibility and degrades gluten, a group of proteins found in grains such as wheat, barley, and rye that are resistant to digestion.
Though not everyone has an issue digesting gluten, people with gluten-related disorders, such as celiac disease and non-celiac gluten sensitivity (NCGS), experience uncomfortable digestive symptoms after ingesting gluten-containing products.
Studies show that sourdough has lower levels of gluten as well as lower levels of other compounds known to cause digestive issues in many people, including Fermentable Oligo-, Di-, Mono-saccharides, And Polyols (FODMAPs) and anti-nutritional factors such as phytates, tannins, and trypsin inhibitors, which can aggravate digestive symptoms in susceptible individuals, such as in those with irritable bowel syndrome (IBS).
This means that sourdough may be easier to digest and result in fewer gastrointestinal symptoms compared to commercially leavened bread.
A 2023 review of 25 studies found that compared to bread made with baker’s yeast, people reported significant improvements in gastrointestinal comfort after ingesting sourdough bread.
Even though sourdough may be easier to digest and result in fewer gastrointestinal symptoms in some people, it may not be the best choice for everyone, especially those with celiac disease who need to completely avoid all gluten-containing products.
A More Bioavailable Source of Nutrients
Anti-nutritional factors, such as phytates, tannins, and trypsin inhibitors, can make it harder to absorb nutrients from food.
For example, phytates found in foods like grains and legumes, bind to certain minerals, such as magnesium, calcium, and iron, blocking their absorption in the digestive tract.
The fermentation process used to make sourdough breaks down anti-nutritional factors such as phytates. In fact, some studies suggest that certain sourdough formulations can degrade over 96% of the phytic acid in the dough.
Certain compounds found in sourdough, such as phytate-degrading enzymes and lactic acid bacteria reduce anti-nutritional factors, improving the availability and absorption of some micronutrients found in the bread, such as iron, calcium, magnesium, and zinc.
Nutritional Facts of Sourdough
The nutrition of sourdough depends on the type of sourdough bread and the ingredients used to make the bread. For example, sourdough made with whole grain flour is higher in fiber and certain vitamins and minerals compared to sourdough made with white flour. Sourdough bread made with enriched flour, which contains added nutrients, will provide greater amounts of B vitamins than bread made with unenriched flour.
Here’s the nutrition breakdown for a medium-sized 59-gram slice of sourdough made with enriched white flour:
Calories: 188
Carbs: 36.5 grams (g)
Fiber: 1.8 g
Protein: 7.67 g
Fat: 1.26 g
Iron: 2.28 milligrams or 13% of the Daily Value (DV)
Copper: 0.088 mg or 10% of the DV
Folate: 82.6 micrograms (mcg) or 21% of the DV
Thiamine: 0.252 mg or 21% of the DV
Niacin: 3.17 mg or 20% of the DV
Riboflavin: 0.218 mg or 17% of the DV
Manganese: 0.33 mg or 14% of the DV
Selenium: 17.5 mcg or 32% of the DV
Zinc: 0.619 mg or 6% of the DV
Breads made with enriched flour are good sources of B vitamins such as thiamine, which is needed for energy metabolism, growth, cellular function, and development, and folate, a B vitamin that’s required for cellular division. Folate also regulates levels of homocysteine, an amino acid that can increase inflammation and oxidative stress when levels get too high in the body. High homocysteine is linked to an elevated risk of several health conditions, including heart disease.
Wheat flour is naturally high in the mineral selenium, which functions as a powerful antioxidant in the body, protecting cells from oxidative damage that may otherwise lead to disease.
Enriched flour also contains added iron, a mineral that’s required for energy production, oxygen transport, and hormone synthesis. Compared to non-fermented breads, the minerals that are found in sourdough, such as iron, may be more easily absorbed by your body as sourdough contains fewer anti-nutrient compounds.
In addition to fiber, sourdough contains natural prebiotics, which are fibers that promote overall digestive health. For example, sourdough contains beta-glucan, a type of prebiotic fiber that’s fermented by bacteria in the large intestine, which releases compounds called short-chain fatty acids (SCFAs). SCFAs benefit gut health by acting as a fuel source for the cells that line your intestinal tract, regulating inflammation, supporting mucus production, and more.
Keep in mind that the nutritional content, including levels of fiber, vitamins, and minerals will vary depending on sourdough ingredients.
Risks of Eating Sourdough
Though sourdough offers several health benefits, it’s not the right choice for everyone.
While sourdough contains less gluten than other breads made with wheat flour, it’s not gluten-free and isn’t safe for people with celiac disease or those who are sensitive to gluten-containing foods.
If you’d like to enjoy sourdough but can’t eat gluten, choose a gluten-free sourdough product. Gluten-free sourdough bread is made with gluten-free flours such as those made with millet, sorghum, teff, quinoa, and buckwheat.
Keep in mind that gluten-free sourdough will have a different texture than sourdoughs made with wheat flour, as gluten adds a chewy and airy texture to baked goods.
Additionally, sourdough is high in carbs and isn’t appropriate for those on very-low-carb diets, such as the keto diet.
Tips for Eating Sourdough
Sourdough has a crisp crust and a chewy and airy texture. It has a characteristic tangy flavor that’s more pronounced in some sourdough breads than others.
Sourdough can be enjoyed in a number of ways and is delicious paired with both sweet and savory ingredients.
Here are some healthy ways to add sourdough into your diet:
Spread sourdough toast with mashed avocado and top with kimchi, red pepper flakes, and a fried egg for a nutritious breakfast or lunch option.
Use leftover sourdough to make croutons for salads.
Use sourdough for sweet dishes like French toast and bread pudding.
Swap regular bread for sourdough when making sandwiches and grilled cheese.
Serve hearty soups, stews, and curries with a side of toasted sourdough.
Toast thinly sliced sourdough and use it on cheese plates and veggie platters.
Sourdough can be purchased at bakeries, farmer’s markets, grocery stores, and online. You can also purchase sourdough starter or make your own at home, which you can use to make your own sourdough bread.
Sourdough starter can be used to make traditional sourdough bread as well as other recipes, like pancakes, muffins, crackers, pizza crust, and pastries.
A Quick Review
Sourdough is a tangy-tasting bread made with naturally occurring yeasts and lactic acid bacteria.
Studies show that sourdough has less of an impact on blood sugar levels compared to refined breads made with baker’s yeast and may be easier to digest as it contains lower levels of gluten, FODMAPs, and anti-nutrient compounds.
Nutrition varies depending on ingredients used, but most sourdough provides a good source of several vitamins and minerals, including B vitamins and selenium.
Though sourdough makes a healthy choice for most people, those who need to avoid or restrict gluten, such as people with celiac disease and gluten intolerance, should avoid sourdough made with gluten-containing flours.