Looks like if you are going to eat bread, from a metabolic standpoint, it doesn't really matter if it is white, wheat or rye.
Dietary breads: myth or reality?
To assess the differences in acute effects of whole wheat bread, wheat bran bread and rye bread--perceived as dietary (Low caloric!) breads--on glucose and insulin levels in patients with type 2 diabetes, as compared to white wheat bread.
One hundred twenty one type 2 diabetic patients were randomized into three groups as whole wheat, wheat bran and rye bread groups. Each group ate 100 g of bread with water with in 10 min. Blood glucose measurements were made at every 30 min in 2 h. Insulin was measured at fasting and at the second hour in the patients who do not use insulin. The same processes were repeated on the following day, with white wheat bread for each group.
No significant difference was found in either glycemic or insulinemic effects between four types of breads when compared to each other (p=0.093 for glycemic effect and p=0.297 for insulinemic effect).
Three different bread types consumed as an alternative to white bread in Turkey, increase blood glucose levels of diabetic patients similar to white bread.