A patient looked it up and sent me this explanation she found. I thought I would post it, it is interesting:

"Why Naturally Leavened Bread?

The fermented quality of naturally leavened bread has several healthful advantages over yeasted breads. Yeasted breads are risen very quickly by a refined yeast strain that has been isolated in a laboratory under controlled conditions, using a process we could never duplicate in our kitchens.

In the process of making sourdough bread, during the rising time (called proofing), bran in the flour is broken down, releasing nutrients into the dough. In particular, the phytic acid (phytin) in grain needs to be 90% neutralized in order for the minerals, concentrated in the bran, to be absorbed by the human body. According to the experiments done in Belgium, phytin can be neutralized by natural bacterial action and to a lesser extent, by baking. In naturally leavened bread, the combination eliminates all phytin, while in yeasted bread about 90% remains.

Furthermore, with sourdough bread, complex carbohydrates are broken down into more digestible simple sugars and protein is broken down into amino acids. Enzymes develop during proofing which are not lost in baking since the center of the loaf remains at a lower temperature than the crust.

It’s the fermentation, partly from lactobacillus, that makes eating good quality bread an aid to digestion of all complex carbohydrate foods including other grains, beans, and vegetables. It helps restore the functioning of the digestive tract, resulting in proper assimilation and elimination. These beneficial bacteria help control

candida albicans, whereas baker’s yeast is a pro-candida organism. This is a brown bread that truly is "the staff of life" as it enhances the whole immune system."

French Meadows spelt is made in this way. This is the one I am most often recommending now, especially since the Pacific went out of business.

Dr.M