The yeast you buy at the store is very convenient and easy to bake with, but because it emits a large amount of gas it makes the grain much less healthy. In sourdough, and in this sourdough pizza, there are two types of organisms - natural yeast and good bacteria. Together they make the bread healthier, easier to digest and more resistant to mold. The acids in the dough make the vitamins and minerals in the flour more available to the body. In addition, the acids slow the rate at which glucose is released into the bloodstream, making sure there are no jumps in insulin levels in the body.
For a sourdough starter recipe, click here.