A number of commercial bread recipes call for "mineral yeast food." It appears to help with a better bread rise. A google search doesn't turn up much information on what this is, where one would get it, or what difference it might make to bread. Here's an example of a commercial recipe calling for "mineral yeast food":
Are there any commercial bakers out there who know what it is, where to get it, and what substitutes might be effective? I'd certainly prefer to use natural things if possible, but I'm not beholden to them.