How much more wheat is in brown bread compared to white bread?

Actually, it's not a matter of how much wheat is contained in the bread, it's the part of the wheat that is used. Whole-Grain bread uses just that, the whole grain, including the fiber-rich outer bran and the vitamin rich middle (the "germ"). The milling process for white flour removes these portions of the grain for ease of cooking and to make more attractive products (white bread can look pretty, right?). But in the process, nutrients such as vitamin E, iron, selenium, fiber, etc. are also removed. Therefore, while you do not receive any more wheat in the diet from eating Whole-Grain (brown) bread, you receive more nutrients.