It has chromium which some think good for glucose metabolism and vits,
especially the b vits among them that are good.  The yeast feeds upon the
sugars of the grains,ie. carbs, and helps reduce them in part.  The
problem area is the carbs in the bread for a diabetic.  I suggest what is
known as "eating to your meter".  This means to set a post meal goal of
some blood glucose level and see what amount of some food does. One
national endo group says 140 bg 2 hours a meal as a max goal, lower is
better.  If you can eat a slice of bread alone or as part of a meal and
not exceed your goal then it is ok, otherwise don't eat it or eat less
until the goal can be met.  Sourdough types breads have a less impact on
post meal bg because the fermentation that occurs aids in this area.  
Whole meal grains, especially rye are better choices for the same reason,
your meter is your friend and will tell the story for you.  The yeast is
really the very least of concerns for a diabetic.

If it replaces baking soda and baking powder, it
is useful for such patients with hypertension.