Proteins are necessary for tissue repair and for the construction of new tissue. Every cell needs protein to maintain its life. Protein is also the primary substance used to replace worn out or dead cells. Your muscles, hair, nails, skin, and eyes are made of protein.
Taking supplemental chromium has been shown repeatedly to improve insulin sensitivity and glucose tolerance, even to the point of reversing type II diabetes in many people (1). Thus, as my old clinical nutrition professor pointed out, apparently a chromium deficiency can actually lead to type II diabetes.
However, eating a diet rich in whole grains (which also tend to be higher in fibre) helps improve insulin sensitivity. This, in turn helps the body more efficiently use blood glucose, controls blood glucose levels and reduces fat deposition. The NHS recommends that you try to choose whole grains as often as possible.