Is Sourdough Bread Gluten-Free?

Sourdough bread made from one of the three gluten grains (wheat, barley, or rye) is not gluten-free, and therefore is likely to make you sick if you have celiac disease or non-celiac gluten sensitivity.

Sourdough bread you make yourself or purchase from the store may have a little less gluten in it (that's a result of the fermentation process that gives sourdough bread it's characteristic tart, sour taste). However, it won't come close to meeting the definition of gluten-free, which in the U.S. is less than 20 parts per million of gluten.

So why does this gluten-free urban legend persist? A quick chemistry lesson may help.

Must-Know Facts About Sourdough Bread and Gluten

The vast majority of sourdough bread — including anything you can buy in the store, unless it's specifically labeled "gluten-free — is made with wheat flour. Wheat, of course, is the primary gluten grain.

To make homemade sourdough bread, you add a starter culture — usually made up of various yeast strains plus lactobacilli, which are forms of friendly bacteria — to the bread dough you made with flour. Then you let the whole mixture sit until the dough rises, and proceed with baking your bread.

This starter culture makes the dough rise like conventional baker's yeast does. Both conventional baker's yeast and sourdough starter cause fermentation in the dough mixture, and the gas byproducts of fermentation are what causes the dough to rise. However, the wild yeast strains and lactobacilli in the sourdough impart a denser feel and a sour taste to the bread...hence the term "sourdough." True sourdough bread tastes nothing like regular white bread.

Why Sourdough Bread Isn't Gluten-Free

It's true that the fermentation process for sourdough bread partially breaks down the gluten in the flour, which is the origin of the claim that sourdough bread is safe for people who have celiac disease or non-celiac gluten sensitivity. However, it only breaks it down partially — not enough to render the wheat-based bread gluten-free (or even close).

The buzz around sourdough as a potential option for rendering wheat-based bread gluten-free comes from some recent research. These studies looked at whether very specific strains of sourdough lactobacilli and yeast could break down the gluten in wheat flour completely if given enough time to work their magic. This process of breaking down proteins into fragments is called hydrolysis.

In one study, people with diagnosed celiac disease were randomly assigned to one of three groups. The first group ate pretty standard gluten-y bread, which had 80,127 parts per million of gluten in it (remember, less than 20 ppm is considered "gluten-free"). The second group ate bread made with flour that had undergone the hydrolysis process "extensively" — the resulting bread had 2,480 ppm of gluten in it (better, but not good enough). And the third group ate fully hydrolyzed bread, which had 8 ppm of residual gluten in it.

Two of the six people who consumed the standard bread discontinued the study early due to renewed celiac disease symptoms, and everyone in that group had positive celiac blood tests and villous atrophy. The two people who ate the intermediate level bread with 2,480 ppm of gluten in it didn't have symptoms but did develop some villous atrophy. But the five people who ate the fully hydrolyzed bread didn't have any symptoms and didn't have clinical signs of gluten consumption, either.

Obviously, this is a very small study, and it's far from definitive. But other research does back up its conclusions. A second project looked at a small group of children and teens who had been diagnosed with celiac and who didn't have any symptoms on the gluten-free diet and reached the same conclusion: sourdough wheat bread made with this extensive fermentation process seemed to be safe, at least in that test group.

A Word from Verywell

Studies into sourdough bread as an alternative for people who have celiac or gluten sensitivity are intriguing. However, the researchers conducting this research have used a specific hydrolysis process created with specially bred strains of yeast and lactobacilli, and this process is not being offered commercially. This is not something you'd be able to try at home, either.

The clinicians involved in these studies have said more research is necessary before they can declare this type of hydrolyzed sourdough bread safe for people with celiac disease. However, interest in this subject is high, so it's entirely possible that we'll see gluten-removed wheat-based sourdough bread on store shelves at some point.