Information on the internet claims that the fermentation of sourdough bread renders the gluten harmless and is it safe to eat for people with celiac disease. This statement has a grain of truth, but must not be taken at face value. It is true that the fermentation of wheat based dough with both wild yeast and good bacteria works to break down the gluten in the wheat.
Tests show that in a controlled experiments, the measurable gluten in fermented sourdough bread can be reduced under 20 parts per million. It is important to note that just because it its possible, every batch of sourdough cannot be tested before you bake or buy. Until the process can be standardized and further studies are done, wheat based sourdough bread is still strictly off-limits for people with celiac disease.
Is it safe for people with celiac disease?
Not yet, but perhaps someday in the future it will be. But right now, there is no standardization for fermentation or preparation of the dough. Without testing, it is impossible to know if all the gluten has been broken down. Additionally, if wheat flour is used in kneading or on baking pans, a significant amount of unfermented gluten has been added back into the bread.
Some online sourdough supporters cite an Italian study that reports 80% of Celiacs eating sourdough bread do not experience adverse symptoms. However, the study also shows that while the subjects may not have symptoms, some did have intestinal damage. It is important to note that long-term exposure to gluten can cause serious health consequences including osteoporosis, other autoimmune diseases and even certain cancers.
How much gluten is safe for people with celiac disease?
The amount of gluten that is safe for someone with celiac disease varies from country to country. The USA guidelines are the highest at 20 parts per million (ppm). To put that amount in perspective, that is equivalent to one drop in a gallon (4.5 liters). The UK sets their limit at 10 ppm and Australia at 0 ppm. It is still unknown if the cumulative effect of consuming small amounts of gluten (under 20ppm) will trigger the autoimmune reaction.
I’m not celiac, can I eat sourdough bread?
The fermentation process does break down some of the gluten, but not necessarily all of it. Traditionally crafted and fermented sourdough bread was tested for gluten content in the USA and found to have less gluten than other types of bread. If you are trying to reduce your gluten intake or are sensitive to gluten, sourdough may be a better option for you. But do not mistake sourdough as being gluten-free. It is simply less gluten.
I am celiac, I really miss sourdough bread.
It is possible to make a sourdough starter and bread completely out of gluten-free grains. Assuming safe kitchen protocol and manufacturing standards, this version of sourdough bread would be gluten-free and safe to eat. A quick search brings up multiple blog posts on the internet with recipes. Let us know if you make a loaf using a gluten-free starter, we would love to hear about it!