Gluten is the characteristic in flour that creates good bread. It is the strands of protein that are created when the dough is kneaded. You want these tight and springy. Since whole wheat flour contains all parts of the wheat kernel, cup for cup it has less protein than white flour (which has had part of the kernel removed).

Added gluten is especially important in whole wheat and dark rye breads.  In these breads, the bran in the flours cuts and damages the existing protein strands as they are being worked.

Adding Vital Wheat Gluten to your whole wheat bread recipe results in improved uniformity and texture.  It provides strength and stretch to dough and also improves yield and shelf life.