What Switching From White Bread to Sourdough Does to Your Body

In recent years, sourdough has become a popular choice for bread lovers. It's also touted as a healthier alternative to white bread, as it's high in essential nutrients. With that in mind, you might consider swapping your usual white bread for sourdough, especially if you'd like to boost the nutritional content of your meals. What will happen if you do? We spoke to dietitians for a deep dive into the potential effects of switching to sourdough.

The Effects of Eating White Bread

Though white bread isn't inherently unhealthy, there are a few things to keep in mind. This type of bread is made of refined flour, which means most of the fiber found in whole grains has been removed. "Because of this, it is digested relatively quickly, which can lead to a faster rise in blood sugar and may not keep you full for long," says Nicole Guzman, MS, RDN, CDN, registered dietitian.

However, white bread can be part of a healthy diet, especially when paired with protein, healthy fats, or fiber-rich foods, which can help slow digestion and improve satiety, Guzman notes. But if you're looking for other options, sourdough is a delicious choice.

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What Happens When You Replace White Bread with Sourdough

If you typically eat white bread, switching to sourdough may have several benefits for your body.

Improved Blood Sugar Control

As mentioned, white bread is digested quickly, which can cause a blood sugar spike after eating. Thus, if you're only eating white bread, especially on its own, it could increase the risk of higher blood sugar levels, says Roxana Ehsani, MS, RD, CSSD, LDN, a registered dietitian nutritionist. This could lead to insulin resistance and type 2 diabetes over time.

Sourdough, however, has a different effect on blood sugar. "Sourdough generally has a lower glycemic index than traditional white bread, which means it tends to cause a slower rise in blood sugar," Guzman says. This is due to the fermentation process required to make sourdough. It "changes the structure of the starches in the bread, which may help slow digestion and glucose absorption," says Guzman.

"This can be beneficial for people with diabetes, pre-diabetes, insulin resistance, or anyone looking for more stable energy levels throughout the day," notes Guzman. 

Better Digestion

The fermentation process used to make sourdough breaks down some of the starches and proteins in the bread, says Ehsani. This can make it easier for many people to digest, particularly when compared to white bread. "Fermentation also produces compounds that may have prebiotic effects and help support beneficial gut bacteria," says Guzman.

"For many healthy individuals, the difference may be subtle. However, people with sensitive digestive systems, IBS, or mild sensitivities to certain carbohydrates may notice less bloating, gas, or digestive discomfort when choosing traditionally fermented sourdough," Guzman says.

Enhanced Nutrient Absorption

Flour naturally contains phytic acid. This is a compound that binds to minerals like zinc, iron, and calcium, potentially making them harder for the body to absorb. White bread is quite low in phytic acid because the refining process reduces it. 

But if you're looking for bread with even fewer phytates, consider sourdough. "The fermentation process of sourdough breaks down phytic acid, which allows certain minerals to be better absorbed by the body," says Ehsani.

Increased Antioxidant Intake

"Sourdough contains higher levels of antioxidants compared to white bread," notes Ehsani. This matters because antioxidants can help protect healthy cells from free radicals, or harmful molecules that cause damage. "You can think of antioxidants as a defense team," says Ehsani. 

This noteworthy antioxidant content is also due to fermentation. In sourdough specifically, the process increases the availability of compounds such as polyphenols and organic acids, which boast antioxidant activity. 

What to Know Before Making the Switch

If you've been buying the same white bread for years, switching to sourdough may come with a learning curve—especially when it comes to choosing authentic sourdough products.

That's why it's worth learning how to identify real sourdough. "True sourdough typically contains just a few simple ingredients," says Guzman. This includes flour, water, salt, and a fermented starter. In contrast, faux sourdough may have a long ingredient list, including commercial or baker's yeast (for leavening) and tangy ingredients (like vinegar or acetic acid).

Also, "terms like 'sourdough flavor' or 'sourdough style' may indicate the bread was made to taste like sourdough without going through the traditional fermentation process," says Guzman. "If you're looking for authentic sourdough, check the ingredient list and look for brands that specifically mention a sourdough starter or long fermentation process. Artisanal bakeries and farmers markets are often more likely to sell traditionally fermented sourdough," Guzman says.

But remember: If you regularly eat white bread, you don't need to replace all of it with sourdough to improve your nutrition. All foods, even white bread, can fit into a healthy diet, says Ehsani. The key is to pair it with a source of fiber and protein, which will provide better blood sugar control, according to Ehsani. "Also, note that simply consuming lots of sourdough won't magically cure your gut health. It's still important to eat a well-balanced diet rich in fiber," says Ehsani.