Grains contain phytic acid which functions as a phosphorus storage, or energy storage, and is present in the bran. This energy storage is very important for grains to be able to sprout. Ruminant animals, like cows for example, produce the enzyme phytase, which is able to break down and digest this compound. Non ruminant animals, like humans, do not produce phytase and are not able to break down phytic acid during digestion.
Why is that bad? To start, phytic acid has a strong binding affinity to important minerals, such as calcium, iron, and zinc. Because we are not able to break down phytic acid, we are not able to absorb minerals which are bound to it. The same compound may also inhibit the action of enzymes needed to digest our food. Including pepsin, amylase and trypsin. These very important enzymes are crucial for the breakdown of proteins and starch.
A diet high in phytic acid can cause many health problems such as tooth decay, osteoporosis, nutrient deficiencies and digestive issues.
Now to the magic of sourdough bread! Probiotic lactobacilli bacteria and other microorganisms are involved in the fermentation of sourdough bread. These organisms are able to produce the enzyme phytase and therefore are able to break down the phytic acid. The fermentation process can significantly reduce or even eliminate the compound. That is why sourdough bread provides easily absorbable minerals and is much easier to digest . Fermentation has also shown to produce beneficial enzymes and other nutrients, specially B vitamins.
What about gluten? The bacteria and yeast involved in the fermentation process are also able to predigest gluten. Studies have shown that the amount of gluten in wheat flour may be reduced from 123 ppm (parts per million) to only 2 ppm after 48 hours of fermentation. This is a reduction of over 98% in gluten content!
This illustrates why many people who suffer from gluten sensitivity are able to eat sourdough bread without negative effects. If you suffer from gluten sensitivity it might be worth experimenting. However, please start with small amounts and wait a minimum of 24 hours to evaluate your body's reaction. Everyone is different and caution is always advisable. The jury is still out on the effects of sourdough bread on Celiac patients. Therefore, they should only try consuming any type of gluten containing foods, fermented or not, under doctor's supervision.
This all seems really good but when you are out in the world be aware. Just because the label says sourdough bread it does not mean that you are getting the real deal. It is much easier to find "fake" sourdoughs out there than the good stuff. The first thing you should always do is check the ingredients. Anytime you see yeast listed as an ingredient you have a fake sourdough.
A starter culture is used to ferment real sourdough bread and it may be listed as an ingredient or not. When they are listed you may find them described as starter culture, sourdough starter or cultured flour. The length of fermentation is of course also important. The longer the dough is allowed to ferment, the lower the phytic acid and gluten contents. During a longer fermentation more beneficial compounds and vitamins are produced. I generally like to consume a bread which has been fermented for at least twelve hours. A fermentation of 36 hours or more is ideal. This information is most times not listed on the label and you might have to call the manufacturer or ask your local bakery to find out.