A sourdough bagel might not be your first choice – but it could be a better option for people looking to improve their gut health.

That’s because of the way sourdough bread is made, using just a handful of simple ingredients.

It has no yeast or chemical additives, like other kinds of bread.

“When buying sourdough, look at the ingredient list,” Hartford HealthCare’s Dr. Ulysses Wu advised.

“The best versions have just flour, water, and salt, and ideally use whole grain flour for added fiber.”

A sourdough bagel could be a healthier choice this National Bagel Day (Getty Images for ESPN)

The secret’s in the starter

Unlike regular bread, sourdough is made using a starter: a live culture of wild yeast and bacteria.

The starter ferments over the course of a week while sitting out at room temperature, producing natural bacteria and yeast.

The yeast produced then feeds on the starches and gluten in the flour, which is what provides the health benefits of sourdough bread, according to University Hospitals Cleveland Medical Center.

That includes the essential minerals zinc, iron and magnesium, that help regulate the immune system and blood flow.

“Fermentation makes sourdough bread easier to digest by breaking down certain carbohydrates that are poorly absorbed in the small intestine. This process can make sourdough a good choice for many people, even those with mild gluten sensitivities,” the center explains.

A sweet truth

The fermentation process is also a boon for your blood sugar levels.

High blood sugar is a risk factor in life-threatening conditions such as heart disease, diabetes and stroke.

But fermentation helps to release sugars more slowly into the bloodstream compared to white or wheat breads.

“Sourdough bread has a lower glycemic index than white bread, so it doesn’t increase blood sugar levels as quickly. This is true because the fermentation process makes starch in the bread less available for digestion and absorption into the bloodstream,” the Mayo Clinic explains.

The fermenting process in making sourdough is what provides a lot of the health benefits (Hans Lucas/AFP via Getty Images)

Feeding the beasts

And, fermentation is also good for digestion and gut health.

There aren’t live probiotics in baked sourdough like there are in the starter, but there are prebiotics: fibers that act as food for the trillions of microscopic bacteria that live in our gut, also known as the gut microbiome.

“A healthy microbiome does more than just support digestion,” Wu said. “Because the microbiome is thought to impact so many different functions, feeding it properly may improve your overall health.”

There are between two and four grams of fiber in sourdough bagels. Breads that are high in fiber can help you stay fuller longer and also play a part in lowering blood sugar.

"Fiber can also help keep blood sugar stable by slowing digestion, help lower blood cholesterol by binding to cholesterol to eliminate it from the body and help with weight management by keeping us full longer after a meal,” MD Anderson Cancer Center’s senior clinical dietitian Grace Whitmer said.