Whole wheat is better than refined wheat, there’s no doubt about that. The biggest problem we have with whole wheat is that it isn’t entirely made from whole grains.
The grains are pulverized into very fine flour, which makes it easy to digest, and this consequently spikes blood sugar. This is no different from eating white bread.
In fact, experts have measured the glycemic index (a measure of how fast foods spike blood sugar levels) in whole wheat bread and it’s just as high as in white bread.