I'm not sure I agree, sorry.
Bread and cereal are both the same 'complex' carb - starch. And starch metabolises to glucose very quickly. If you lick a piece of bread (of any colour) or potato, within five minutes, the area you lick will smell sweet because the amylase in saliva breaks down starch to glucose. In other words, the conversion process to glucose begins before you even swallow the food!
The difference is whether you are eating grains in their raw form - they obviously have a fibrous shell which slows down their digestion. But in foods like cereal or bread, these are processed, thus breaking down the shell. Eating wheat seeds is one thing. Eating Shredded Wheat is quite another.
I take on board the point that foods with a higher fibre content (say, wholemeal bread, all-bran) will generally have lower GIs but in my personal experience, a slightly higher level of fibre doesn't make a substantial difference to the end result on my blood sugar. Fruit is low GI, technically, but my experience with many supposedly low-GI fruits tells me that low GI does not necessarily indicate being easier on blood sugar.
This may not be the case for everyone, so the central point is that if your food has had any sort of preparation and contains carbohydrates of any kind, you need to test and see its effect on you - you cannot safely assume that because something is low-GI, wholegrain or 'brown' that it will always be better for you than a 'white' alternative.
