Rye bread is a type of bread made with various proportions of flour from rye grain. It can be light or dark in color, depending on the type of flour used and the addition of coloring agents, and is typically denser than bread made from wheat flour. It is higher in fiber than white bread and is often darker in color and stronger in flavor. Rye bread has a low glycemic index, which means it does not cause a spike in blood sugar when compared to white bread. ~ http://www.nutritionj.com/content/8/1/42
Rye flour has a lower gluten content than wheat flour, and contains a higher proportion of soluble fiber. Thus, rye bread, including pumpernickel, is a widely eaten food in Northern and Eastern Europe. Rye flour is high in gliadin but low in glutenin. It therefore has a lower gluten content than wheat flour. It also contains a higher proportion of soluble fiber. ~http://www.sciencedirect.com/science/article/pii/S003194229900196X
My sweetie likes a good bacon and feta pump. I buy thick cut double smoked bacon to lay over a slice of dark pumpernickel, then I crumble on some feta or whatever cheese on the bacon along with sliced red onion or even dried fruits and cover with another slice of pumpernickel bread. If you like, warm it up by wrapping in wax paper to microwave for 25-30sec. or grilling ~ Yum!