If there is one food you should eat even though it pushes the upper limit of glycemic load, it's All-Bran cereal. It is by far the best source of insoluble fiber in the Western diet. In fact, it is difficult to get enough of that kind of fiber without eating bran.

There are two kinds of fiber, soluble and insoluble. While there is plenty of soluble fiber in fruits and vegetables, insoluble fiber is hard to come by.

In addition to meat, our ancestors ate crude vegetation--grass, bark, roots and unripened fruit and berries--which contained large amounts of insoluble fiber. Over the millenia, we humans have refined most of the insoluble fiber out of our diet. However, it is essential for good colon health.