I have found the entire subject of breads and diabetes fascinating. It has cost me a small fortune in strips testing them, usually several times. The biggest problem is not knowing what is in the bread, despite the claims made*.
Artisan bread bakers do some excellent loaves but even with loaves with a high rye content, BG can still spike quickly. The 100% dark ryes are bar far the best. Some bakers who do a low GI loaf which looks more like a brown loaf are also very good. I however suspect that there is more to it than just the grains. The yeast and gluten content play an indirect part. Generally, bakers yeasts are to either be avoided or used only in small quantities. Leavens, sourdoughs, bigas etc seem to be safer. Sourdough breads tend to state what they are, the others, sponges and poolishes etc don't. Commerical processes mean that it is quicker and easier for a commercial baker to bung yeast and sugar into a loaf in order to get a quick rise. Good bread needs time. Leavens and sourdoughs start with cultures which use the natural yeasts found with the grains and produce a number of enzymes and acids which interact with not only the choice of grain, but also in the way those grains have been milled. The acidic content may, in my opinion, help with insulin sensitivity.
I am experimenting with different bread cultures at the moment and, when they are ready, I shall try them on different grains and combinations. If in the meantime there are any other hobby bakers reading this thread, please share your knowledge. Life is so much easier if you can make sandwiches for a meal so finding suitable breads is worth the effort.
Andrew Whitely, author of the book Bread Matters, has a website for those interested.
http://www.breadmatters.com
* A wholegrain of truth? Industrial loaf names, claims and contents
http://www.sustainweb.org/publications/?id=266