Sourdough bread is an old favorite that has recently risen in popularity. Many people consider it to be tastier and healthier than conventional bread. Some even say that it’s easier to digest and less likely to spike your blood sugar. But is there any truth to these claims? This article takes a close look at the evidence.
What Is Sourdough Bread?
Sourdough is one of the oldest forms of grain fermentation. It’s believed to have originated in ancient Egypt around 1,500 BC and remained the customary form of bread leavening until baker’s yeast replaced it a few centuries ago.
A leavened bread is a bread whose dough rises during the bread-making process as a result of gas being produced as the grain ferments. Most leavened breads use commercial baker’s yeast to help the dough rise. However, traditional sourdough fermentation relies on “wild yeast” and lactic acid bacteria that are naturally present in flour to leaven the bread.
Wild yeast is more resistant to acidic conditions than baker’s yeast. This is what allows it to work together with lactic acid-producing bacteria to help the dough rise. Lactic acid bacteria can be found in several other fermented foods, including yogurt, kefir, pickles, sauerkraut and kimchi.
The mix of wild yeast, lactic acid bacteria, flour and water used to make sourdough bread is called a “starter.” During the bread-making process, the starter ferments the sugars in the dough, helping the bread rise and acquire its characteristic taste.
Sourdough bread takes much longer to ferment and rise than other types of bread, which is what creates its particular texture. To this day, making sourdough bread remains popular in Mediterranean and Middle Eastern countries. However, some store-bought sourdough breads are not made using the traditional sourdough method, thereby reducing their health benefits.
Buying sourdough bread from an artisan baker or a farmer’s market increases the likelihood of it being “true” sourdough bread.
The nutrition composition of sourdough bread depends on the type of flour used to make it — whether it’s whole grain or refined. Nevertheless, sourdough’s nutrition profile resembles that of most other breads.
On average, one medium slice weighing approximately 2 ounces (56 g) contains (2):
• Calories: 162 calories
• Carbs: 32 grams
• Fibre: 2–4 grams
• Protein: 6 grams
• Fat: 2 grams
• Selenium: 22% of the RDI
• Folate: 20% of the RDI
• Thiamine: 16% of the RDI
• Sodium: 16% of the RDI
• Manganese: 14% of the RDI
• Niacin: 14% of the RDI
• Iron: 12% of the RDI
In addition, sourdough has some special properties that allow it to surpass the nutrition profile of most other types of bread, which is discussed in the next chapter.
It’s More Nutritious Than Regular Bread
Although sourdough bread is often made from the same flour as other types of bread, the fermentation process improves its nutrition profile in several ways. For starters, whole grain breads contain a good amount of minerals, including potassium, phosphate, magnesium and zinc. Unfortunately, the absorption of these minerals is limited by the presence of phytic acid, which is commonly referred to as phytate.
Phytates are considered anti nutrients because they bind to minerals, reducing your body’s ability to absorb them. Interestingly, the lactic acid bacteria found in sourdough bread lower the bread’s pH, which helps degrade phytates. This results in a bread that has a much lower phytate content than other types of bread.
One study showed that sourdough fermentation may reduce the phytate content of bread by 24–50% more than conventional yeast fermentation. Lower phytate levels increase mineral absorption, which is one of the ways in which sourdough bread is more nutritious than conventional bread.
Moreover, studies show that the lactic acid bacteria present in sourdough bread have the ability to release antioxidants during sourdough fermentation. Sourdough fermentation also increases folate levels in the bread, although levels of certain nutrients like vitamin E may be slightly reduced in the process.
Finally, sourdough’s longer fermentation time helps improve the flavour and texture of whole grain bread. This may make people more likely to opt for a whole grain bread, thereby promoting a higher consumption of fibre and nutrient-rich breads.
In summary sourdough bread contains higher levels of folate and antioxidants than other breads. Also, its lower phytate levels allow your body to absorb the nutrients it contains more easily.
It’s Easier to Digest
Sourdough bread is often easier to digest than bread that’s fermented with brewer’s yeast. Researchers believe this could partly be due to sourdough bread’s prebiotic content and probiotic-like properties. Prebiotics are non-digestible fibres that feed the beneficial bacteria in your gut, while probiotics are beneficial bacteria found in certain foods and supplements.
Regularly consuming both may help improve your gut health, easing digestion. Sourdough fermentation may also degrade gluten to a greater extent than baker’s yeast. Gluten is a type of protein found in certain grains. It can cause digestive problems in people who are sensitive or allergic to it.
Gluten tolerance varies from person to person. Some have no visible issues digesting gluten, whereas it can cause stomach pain, bloating, diarrhoea or constipation in others. Sourdough bread’s lower gluten content may make it easier to tolerate for individuals sensitive to gluten.
Research has shown that the sourdough fermentation process may also help improve the taste, texture and nutrient availability of gluten-free bread. This makes gluten-free sourdough bread a possible option for gluten-sensitive people. However, keep in mind that sourdough fermentation does not degrade gluten completely. Sourdough bread containing wheat, barley or rye should be avoided by people with gluten intolerance or celiac disease.
In Summary sourdough bread contains lower amounts of gluten and its prebiotic- and probiotic-like properties may help improve digestion.
It May Be Better for Blood Sugar Control
Sourdough bread may have a better effect on blood sugar and insulin levels than other types of bread, though the reason for this isn’t yet fully understood. Researchers believe that sourdough fermentation may modify the structure of carb molecules. This reduces the bread’s glycemic index (GI) and slows down the speed at which sugars enter the bloodstream.
The GI is a measure of how a food affects blood sugar. Foods with a lower GI are less likely to produce a spike in blood sugar levels. In addition, the lactic acid bacteria found in the dough produce organic acids during fermentation. Some researchers believe these acids may help delay stomach emptying and prevent a spike in blood sugar in a way similar to vinegar.
The sourdough fermentation process is often used to make rye breads, as rye does not contain enough gluten for baker’s yeast to work effectively. One study showed that participants who consumed rye bread had a lower spike in insulin levels than those given the same amount of conventional wheat bread. In addition, several other studies compared participants’ glucose response after eating sourdough bread and bread fermented with baker’s yeast.
Overall, participants who ate the sourdough bread had lower blood sugar and insulin levels than those who ate the breads fermented with baker’s yeast.
In summary sourdough fermentation produces changes in the bread that may allow for better blood sugar control and improved insulin sensitivity.
The Bottom Line
Sourdough bread is a great alternative to conventional bread. Its lower phytate levels make it more nutritious and easier to digest. Sourdough bread also seems less likely to spike your blood sugar levels, which makes it an option for those monitoring their blood sugar.
All things considered, it’s worth giving it a try.
Just remember that sourdough bread can be made from virtually any type of flour, so opt for a whole grain variety.
Our thanks to Alina Petre for this article.
Alina Petre MS, RD (CA)
Alina is a registered dietitian with an expertise in sport nutrition. She completed her nutrition undergrad in Canada, received her Master’s degree in the U.K. and currently calls the Netherlands home. In her free time, Alina loves exploring new corners of the world, especially if they include a good wave to surf or a nice slope to descend. Alina loves wholesome foods, working up a sweat, and taking care of our planet.