Commercial yeast is made from hops used for making beer. Nothing inherently wrong with that. It speeds up the rising process so much that it doesn't allow the time needed to break down the grain into something more usable for our bodies. I just finished reading
Vintage Remedies Guide to Bread. Jessie Hawkins does a great job explaining the process and results of both methods of bread making. And she gives you instructions for starting your own starter and for making all kinds of things with it.