Sourdough is a naturally fermented type of bread made with wild yeast and lactobacilli.
It is common to hear assertions that sourdough bread has superior health benefits compared to bread made with commercial yeast.
But do these claims stand up to scrutiny?
This article delves into the nutritional properties of sourdough and investigates the scientific research surrounding its purported health benefits to provide an answer.
Is sourdough bread a healthier choice than bread made with commercial yeast?
What Is Sourdough Bread?
First, let’s explore what sourdough bread is and how it’s made.
Sourdough is a traditional way of making bread that has been practiced for thousands of years. On this note, historical records demonstrate that the ancient Egyptians were making sourdough bread as far back as 2000 BC (1).
The process involves pre-fermenting a starter mixture that typically contains flour, water, salt, wild yeast, and strains of lactobacilli. Lactobacilli strains, belonging to the lactic acid bacteria family, produce lactic acid during fermentation (2).
Following this fermentation, the sourdough bread is shaped and left in a warm environment. This stage of the process is known as proofing, which allows the bread to rise as fermentation continues (3).
Once proofing is complete, the sourdough is baked in the oven.
As a result of the fermentation process, sourdough bread acquires a slightly tangy flavor and often boasts a chewier texture compared to most commercial bread (4).
Furthermore, sourdough bread typically has a more uneven, irregular texture characterised by large holes formed by air pockets. These air pockets are a result of carbon dioxide produced by the sourdough bacteria during fermentation.
The following image demonstrates the bread’s characteristic texture:
In contrast to the commercial yeast bread found on supermarket shelves, sourdough undergoes a longer fermentation time and typically excludes additional ingredients like sugar and fat.
Additionally, commercial yeast bread relies on standardised baker’s yeast rather than the wild yeast and lactobacilli bacteria used in sourdough.
Key Point: Sourdough is a traditional bread crafted through a natural fermentation process using wild yeast and lactobacilli bacteria.
Does Sourdough Bread Have Any Benefits?
Now that we know what sourdough bread is, let’s explore whether it has any documented benefits.
Taste
First of all, it is worth acknowledging the taste ‘benefit’ that sourdough brings to the table.
Many people appreciate the range of flavors sourdough provides, contrasting with the simple taste of commercial yeast bread.
A sourdough survey conducted by the ‘Real Bread Campaign’ gathered responses from 77 bakers, revealing a rising trend in sourdough bread sales, primarily attributed to its flavor. Participating bakers noted that customers often express a taste preference for sourdough, with one adding “once people try sourdough, they often prefer the texture, taste and keeping ability” (5).
Key Point: Sourdough’s complex flavor profile is superior to that of commercial yeast bread, and most consumers prefer its taste.
Lower Phytic Acid Content
Another potential advantage of sourdough bread lies in its reduced phytic acid content (6, 7).
Phytic acid is a compound abundant in numerous plant foods like grains, legumes, nuts, and seeds.
While phytic acid has a range of potential benefits and downsides, it is known for its effects as an anti-nutrient. This is because phytic acid can bind to minerals such as calcium, iron, magnesium, and zinc, reducing the amount of these minerals we can absorb (8).
Thus, the phytic acid content of bread reduces the bioavailability of calcium, iron, magnesium, and zinc naturally contained in the bread.
During sourdough fermentation, the lactic acid bacteria produce phytase, an enzyme that breaks down phytic acid (9, 10).
Consequently, sourdough bread boasts greater bioavailability of calcium, iron, magnesium, and zinc compared to commercial yeast bread (11, 12).
A 2001 study demonstrated a 62% reduction in phytic acid content in sourdough bread compared to a 38% reduction in bread fermented with regular commercial yeast (13).
To summarize, opting for sourdough likely enhances mineral absorption from bread.
Key Point: Sourdough’s fermentation process more significantly diminishes phytic acid levels than commercial yeast bread. This enhances the bioavailability of essential minerals in the bread.
Does Sourdough Bread Have Benefits For Blood Sugar Control?
Although both sourdough and commercial yeast breads predominantly consist of starchy carbohydrates with similar carbohydrate content, research indicates a potential advantage for sourdough in blood sugar control and type 2 diabetes management.
A 2024 systematic review evaluated the evidence from clinical trials on sourdough bread’s impact on glycemic control, comparing it to commercial yeast bread (14).
Interestingly, the review revealed that sourdough bread elicited a lower average blood glucose response 60 minutes post-consumption compared to commercial yeast bread. Furthermore, 120 minutes after sourdough bread consumption, blood sugar levels were either the same or lower compared to other types of bread.
However, it should be noted that the researchers assessed the certainty of evidence as being “low to very low.”
With this in mind, we should refrain from making definitive statements on sourdough’s efficacy for blood sugar control. Larger randomized controlled trials are necessary to provide greater clarity.
Key Point: Evidence suggests that sourdough bread might offer slight advantages in blood sugar control. However, the certainty of evidence has been rated as low to very low.
Does Sourdough Bread Contain Beneficial Probiotics?
Probiotics are a type of live bacteria that can potentially have health benefits, holding particular promise for digestive health and the gut microbiota. For this reason, they are sometimes referred to as “good bacteria” (15, 16).
We can find probiotics in various fermented foods such as kefir, kimchi, sauerkraut, and yogurt (17).
While sourdough bread’s starter mix contains live lactobacilli bacteria, unfortunately, the high heat baking process destroys these probiotics (1).
That said, intriguing preliminary research on ‘heat-killed probiotics’ suggests they may have potential benefits.
Heat-killed probiotics are also known as ‘non-viable probiotics’ or ‘heat-inactivated biotics.’ Though they are not ‘live’ and further research is warranted, these heat-treated probiotics retain certain characteristics, such as their cell wall components, and may still offer benefits for the immune system (19).
Key Point: Sourdough bread’s live probiotics are lost during baking, but heat-killed probiotics may still offer some health benefits. Further research in this area is ongoing.
The Nutritional Values of Sourdough Bread Depends on the Type of Flour Used
A critical aspect to consider regarding the nutritional benefits of sourdough bread is the specific flour used to make the bread.
For example, sourdough can be made with wholegrain wheat flour or rye flour, or white (wheat) flour. As with commercial yeast bread, the choice of flour significantly impacts the bread’s nutritional profile.
Rye bread and whole grain wheat bread, for instance, offer higher levels of fiber, protein, vitamins, and minerals compared to white bread.
For a detailed nutritional comparison between rye bread and white bread, please refer to the following article:
In short, opting for regular rye bread would arguably be a better nutritional choice compared to white sourdough bread. Similarly, sourdough crafted with whole wheat flour or rye flour typically offers more nutritional value than its white flour counterpart.
Based on USDA data, here are the calorie, protein, and fiber content of rye, whole wheat, and white bread per 100 grams (20, 21, 22):
White bread: 267 calories, 9.43g protein, 2.3g fiber
As evident from the data, whole wheat and rye breads contain fewer calories and more fiber than white bread. The same holds true for sourdough bread made using these flours.
Glycemic Impact
It’s noteworthy that research indicates bread made from whole wheat flour or rye exerts a lower glycemic impact compared to white flour bread, particularly when the former has larger whole grain particles rather than being finely milled (23, 24, 25, 26).
In simpler terms, sourdough made with rye or whole wheat flour should elicit a lower blood sugar response post-consumption compared to white bread.
Key Point: Sourdough made with rye flour or whole wheat flour offers better nutritional value than sourdough made with white wheat flour.
Does Sourdough Bread Have Any Downsides?
When comparing sourdough bread to commercial yeast bread, there are no nutritional drawbacks.
However, there are some other considerations to take into account.
Sourdough Costs More
One notable downside for many people is the price difference. Sourdough bread typically commands a premium price, being significantly more expensive than its commercial yeast counterpart.
This cost difference largely stems from the time it requires to produce sourdough. Furthermore, mass-produced commercial yeast bread benefits from economies of scale, keeping its price down.
While sourdough’s superior taste and potential health benefits may justify its higher cost for some, others may understandably find the price difference prohibitive.
Sourdough Bread Contains Gluten
Another factor to bear in mind is that regular sourdough bread, being a wheat (or rye) product, is still a source of gluten.
As such, it’s unsuitable for individuals with celiac disease or those with gluten sensitivities (27).
That said, sourdough bread can be gluten-free if made with a gluten-free flour. A quick online search should help locate local producers offering gluten-free sourdough options.
Key Point: Some potential drawbacks of sourdough bread may include its higher cost compared to commercial yeast bread and its gluten content, making it unsuitable for some individuals.
Is Sourdough Bread Healthier Than Commercial Yeast Bread?
Opting for sourdough over commercial yeast bread typically means choosing a product with fewer additional ingredients, which may appeal to some consumers.
Moreover, research suggests there may be some positive aspects of the bread, such as its lower phytic acid content and potential benefits from its heat-inactivated probiotic content.
There are also some indications that sourdough may have a lower impact on blood sugar compared to commercial yeast bread, although the evidence for this remains uncertain.
Overall, when evaluating the healthfulness of any bread, the biggest consideration should be the flour its made with.
Breads made with rye and whole wheat flours offer more nutritionally than white bread, regardless of whether the bread is sourdough or not.
Michael works as a nutritionist in a community setting and holds a Master's Degree in Clinical Nutrition. He believes in providing reliable and objective nutritional information to allow informed decisions.
