Here here Derleth says about bread baked with bleached white flour compared with bread baked with whole grain flour, “It’s too easily digested, turning to something not much better than sugar and filling the blood with glucose.” This, I fear, sounds fishy to me, like one of the scary and baseless stories told by people in the natural foods industry, and I have always assumed that the carbohydrates themselves are the same but I could be wrong so I’m asking you folks. Is it true that the white stuff breaks down faster than the tan stuff when they are ground to the same fineness? If so, why?
Of course, THIS part is true:
since ALL carbohydrates have to be broken down into become glucose for you to use them…
Here’s a study suggesting that it does:
http://www.cbsnews.com/stories/2004/11/05/health/webmd/main653957.shtml
More on the glycemic index:
http://www.cbsnews.com/stories/2004/11/05/health/webmd/main653957.shtml
I’m sorry that this reply is not as detailed as it should be. I’m afraid I don’t have enough time nor detailed knowledge to do it justice, but I will give you some hints that should allow you to dig up some useful & relevant info.
It has to do with the respective glycemic indexes of whole grain vs white flour. The glycemic index measures how fast a given food & its carb components are metabolised. At one end, you have pure refined glucose, which is absorbed very fast, and runs out also very fast. At the other end are the more complex carbohydrates that take more effort to metabolise and are thus absorbed over a loger time. These give you a more gentle energy ramp-up and let down. This is something to which diabetics have to pay close attention, as two foods with the same calory content but different glycemic indexes can affect blood glucose levels very differently over a given period of time.
It has been suggested that a more “resonable” approach to diet modification is to try to increase the proportions of more complex carbs in the total carb intake, rather than eliminating carbs alltogether a la Atkins.
My recollection is even shakier here, but I seem to remember that the higher blood sugar peaks from more simple carbs trigger the “engergy storage in fat cells” phenomenon, vs. just using the food energy in daily activity that a lower, but more stable, blood sugar level from more complex carbs, hence the weight reduction / maintenance benefit.
Anecdotally, I can tell you that since we have tried do do this in our home, I find I can last much longer without needing a snack between meals, and I don’t get that yucky sensation of feeling faint / dizyness / getting the shakes I used to get if I delayed or skipped a meal.
Can any diabetics / more knowledgeble dopers correct / confirm this?
Whew, gotta love the 'dope. cher3 beat me to the punch with even more details by 3 minutes. 
I love it when I turn out to be right! Okay, what the Glycemic Index (search term “flour”) folks say is that Wonder Bread has a glycemic index of 73 while the American bread they tested that was made from whole wheat flour with no crunchy things that take longer to digest has a glycemic index of . . . 73. Fully supporting my assumption that there is NO DIFFERENCE between the two as far as carbohydrate absorption is concerned. Of course, by using a grain other than wheat and/or busting the grains into larger chunks you can slow the absorption considerably (a word to the wise diabetic Dopers) and whole wheat flour has many other advantages but if your object is to absorb your carbs as slowly as possible using whole wheat flour instead of the nasty bleached white stuff will not help.