Sadly the issue with most breakfast cereals isn't the sugar content on its own, it's the highly processed nature of the product that massively increases the GI. Even Bran Flakes and Shredded Wheat suffer from this. In many ways it's very like the issues with bread.
I quote "Tim2000s" because he is my inspiration to elaborate a little on this topic. Indeed, "Tim 2000s" is, again, very accurate as the problem is with the industrial processing of the grains.
Breakfast cereals are highly processed carbohydrates.
Almost all boxed cereals are highly glycemic and have a high glycemic load.
Kellog’s All Bran takes the prize of a highly processed carbohydrate which is low both in its glycemic index and its glycemic load. This is the reason why when you eat it, tastes like you are eating the box.
On top of the processing, in order for companies to make cereals taste good, they add sugar.
And because of the processing, the nutritional value of these cereals is next to nothing. The highly processed grains that are used to make the cereal have had all the quality nutrients removed. This is the reason why companies need to fortify their cereals.
The best cereals are the old fashioned ones, like coarse oatmeal, as mentioned by another Forum member above.
The grain is intact and has had minimal processing; therefore, the blood sugar rise, after consumption, will be milder and steady.
"Tim2000s" also mentioned bread (and, again, so accurately).
Most of us use brown bread believing that it is healthier. In fact, brown bread is a complete fake out.
Actually, in the U.K. market, there is no "real" brown bread. Whole wheat bread is highly processed, just like white bread is. No matter how the industry wishes to name it (whole meal, granary sensations, brown… whatever) the fact is that the processing is there and this bread will make our blood sugar spike as much as white bread will (or sugar or potatoes). When making bread, most brands use whole meal flour combined with white flour in order to make bread fluffier. Bread that is made only by whole grains is coarse and dry and doesn’t sell too well. Some companies take this even further, as their breads are simply white processed ones with the addition of food colorings.
Alternatively, in order to avoid blood sugar spikes we need to eat wheat, rye or barley, in the "old-fashioned" way like “peasants” used to eat centuries ago. This means bread which is made using the actual whole grains and not flour (regardless if the flour is white or brown, it is still processed).These grains should be stone-ground and not the result of high speed grinders. Even if you decide to make your own bread at home using brown flour, the fact that you will use processed flour will make no difference.
The good nutritional choice when it comes to bread is coarse wheat kernel bread (with intact kernels) and coarse rye kernel (pumpernickel) but I haven’t managed to find a brand which produces them in the U.K. so far…Their glycemic index is around 41 and their glycemic load is 5.
Similarly, oat bran bread is a good choice. Sour dough bread and Ezekiel bread and German bread are also good unprocessed choices. I have not managed to find any of these in the U.K. to be honest.
So, if you don’t consume these types of breads, whatever other bread you use (regardless how it is branded, regardless what the color is, regardless if it is infused with some whole seeds to look better) will make no difference to white processed bread.