DNC News


Sourdough Bread and Celiac Disease

Jacob Schor, ND

April 5, 2007



It is Passover, the holiday in which we eat only unleavened bread and as a result I find myself thinking constantly about bread and bread.


The art of baking leavened breads dates back nearly 10,000 years to ancient Egypt . So also does the practice of brewing beer. The ancient Egyptians were serious beer drinkers, fermented beverages made from grain were a mainstay of their diet. Some theories credit alcohol production as the primary impetus for hunter gathering peoples to abandon their way of life in favor of farming. Those who farmed had an ample supply of grains and could have all the beer they wanted.


Leavened bread was probably an accident. Living and cooking amid vats of brewing beer, it was only a matter of times until yeast got into the dough and a lucky baker found that the bread had gone puffy. Though accidental at first, early bakers quickly discovered that it was more reliable to use a starter, a bit of uncooked dough saved from the previous day's baking. These bread starters are what we now call sourdough starters. These are not pure yeast cultures but mixtures of yeast and bacteria, usually lactobacilli bacteria, the kind we associate with yogurt or healthy digestion. Yeast eats sugar and releases carbon dioxide which gives the ‘rise' to bread dough. But by itself yeast will not break down the starches in flour. This is why bread recipes call for a little sugar or honey. You need sugar to feed the yeast. Modern commercial flour often has some malt added; this releases sugar from the flour. Before sugar and malt, bakers relied on sourdough starters.


The yeast and bacteria in sourdough live in a happy relationship. The bacteria digest the flour releasing sugar which the yeast eat, releasing carbon dioxide. The carbon dioxide is trapped in the protein strands formed by the gluten proteins in the flour causing otherwise heavy and dense dough to become spongy and light. When the bread bakes in a hot oven, these bubbles of trapped gas and moisture expand rapidly causing the bread dough to become even more airy. The lactic acid and other chemicals produced by the bacteria give the finished bread their particular sour flavors. Variations in the bacteria species used account for the different flavors of various sour dough breads.



While bakers made bread using sourdough starters for close to ten thousand years, it is only in the last hundred or so years that they have used purified yeast. Having ready made pure yeast reduces the time it takes to make bread and results in a mild (some would say bland) tasting bread.


During these last hundred years, celiac disease has appeared in our medical texts. Of course, it may have been around much longer, but curiously, there is little mention of it. Celiac disease was first described accurately in the early 1950s by Dr. Willem Karel Dicke, a Dutch pediatrician, who recognized that the disease is caused by the ingestion of wheat proteins. This disease appears to be getting more common. My old Merck Manual from the mid 1980's put the incidence at about 1 in 1200 people. A recent bakery trade journal puts the incidence at about 1 in 50. This increased incidence may simply be greater awareness and a greater likelihood of recognition. Yet one has to wonder.


There is a fascinating paper on sourdough and celiac disease. Italian and Irish researchers have found that some lactobacilli bacteria in sourdough can digest and modify the gluten proteins in flour to the extent that a person with celiac disease may be able to eat them without ill effect.



Rafaella di Cagno and her colleagues set out to produce a bread well tolerated by people with celiac disease. They selected specific sourdough bacteria that were especially good at breaking down the chemical bonds in wheat gluten that trigger the celiac immune reaction in people with the disease. They were able to show experimentally that fermentation with these specific lactobacilli completely inactivated the particular peptides that cause the reactions. The researchers then baked sourdough breads using a mixture of wheat, oat, millet, and buckwheat flours. After 24 hours of fermentation, wheat gliadins were almost totally broken down. When tested they had less than 1/250 the action of proteins from bread dough made with baker's yeast.


The researchers then baked two types of bread, one made with baker's yeast and the other with this special lactobacilli bacteria. The researcher fed their bread in a double-blinded fashion to 17 patients with celiac disease. Thirteen of the 17 patients showed a “marked alteration of intestinal permeability after ingestion of baker's yeast bread.” That is a fancy way of saying it messed up their guts. However, when fed the sourdough bread, the same 13 patients had no measurable changes in their gut permeability. In other words, the sourdough bread didn't bother them.

“These results showed that a bread biotechnology that uses selected lactobacilli, nontoxic flours, and a long fermentation time is a novel tool for decreasing the level of gluten intolerance in humans.” [i]



This information of course raises the question whether part of the increased incidence in celiac disease is just the result of the decreased use of sourdoughs to bake bread. Replacing sourdough with commercial yeast probably has increased the exposure of people to celiac triggering proteins that now remain undigested.



Personally I love the flavor of a well made sourdough bread and over the last 35 years have obtained, used and then lost sourdough starters beyond count. Some have produced delicious breads, some not.


Sourdough from different parts of the world have distinctly different flavors because they have different strains of lactobacilli bacteria and yeast both of which produce flavor. A loaf of San Francisco sourdough tastes different than a German sourdough. Some of these starters have been in continuous use for hundreds of years. The bacteria and yeast have evolved together adapting to their symbiotic relationship and producing distinct flavors. If they don't taste good, they are discarded. The good tasting starters are preserved and treated like family heirlooms.


Homemade sourdough bread:

You can find instructions posted on the internet for making your own sourdough starter; typically this involves capturing wild yeasts from musty grape skins and bacteria from either rye flour or yogurt. Such starters often lack the ‘mellow' flavor of a long used starter. My suggestion is ignore these homemade starters and get an ‘established' starter. One website, Sourdough International, sells a dozen or so distinctly different sourdough ‘starters' which have been collected from all over the world. http://www.sourdo.com/culture.htm


Up until Passover curtailed my baking experiments, I have been using Carl's 1843 Oregon Trail sourdough starter. Ancestors of the late Carl Griffith's apparently brought this starter to Oregon in 1843 in their covered wagon. While alive, Carl Griffith mailed sourdough starters free to anyone who requested them. When he passed away in 2000, his ex-wife continued the tradition until her death in 2003. Now their friends continue the tradition of sending out free sourdough. See: http://home.att.net/~carlsfriends/

They don't charge anything, asking only a self-addressed postpaid envelope. I have found it very reliable, easy to work with and of mild flavor. If you like your sourdough bread to taste sour, you may not be as happy with this one.  If you are interested in making breads that don't have the sour tang, than this one is ideal. 


Yet another source for a sourdough starter with instructions for use: http://forums.egullet.org/index.php?showtopic=27634


All of these websites offer plenty of recipes to use in baking bread so I won't detail recipes here. One trick that I learned recently from Cooks Illustrated magazine is to refrigerate the shaped loafs overnight before letting them rise the final time. Admittedly there is never enough room in the refrigerator for these loaves, doing so allows the bread time to develop a stronger more intense flavor.


It is almost impossible to make a decent bread our of just rye flour using baker's yeast alone. The protein structure of rye flour will not trap air bubbles from the yeast and most attempts will produce a loaf similar in consistency to a brick. Fermentation of rye flour with lactobacilli though changes the protein structure so that it will trap air and 100% rye flour sourdough breads can be quite good. Dimmers, a wholesale bakery here in Denver , makes an excellent 100% rye loaf that is available at select stores in town. You can call them at (303) 399-3101 and ask which stores near you carry it.


Although Matzo may be called, ‘the bread of our affliction' it doesn't taste all that bad and eating it a week or so each year isn't that great a hardship. Still, come next week, I'll have a new batch of sourdough fermenting in the kitchen.


[i] Raffaella Di Cagno et al. Sourdough Bread Made from Wheat and Nontoxic Flours and Started with Selected Lactobacilli Is Tolerated in Celiac Sprue Patients. Applied and Environmental Microbiology, February 2004, p. 1088-1096, Vol. 70, No. 2



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