Fiber will help regulate D and C, but you may have to keep wheat bread to a minimum. Since you have not had any for a while, the enzymes needed to digest it are probably available in your system. If you start eating a lot of it, you may run out of those enzymes and that can be a problem. Wheat has a number of things in it that makes it hard to digest, including amylase inhibitors and lectins and the gluten is not digested if the starch is not being digested because of amylase inhibitors. The lectins directly damage your gut lining and undigested starch and protein can cause bacterial overgrowth. Small amounts may be tolerated.