While it would be premature to answer yes to this question, it does appear that certain compounds can favorably impact the blood sugar and may have the potential to delay or prevent diabetes. Those for whom there is at least some evidence include uncooked walnuts, gymnema sylvestre (also known as gurmarbooti or gurmar), green tea, and certain compounds of chromium, zinc, and vanadium. While it is not known how most of these compounds work, the metallic compounds may work by facilitating the body’s mechanisms for releasing insulin, or responding to insulin.
Overall, the effect of most of these items is quite mild, and they may influence the blood sugar by a few points. How-ever, occasional individuals have a fairly dramatic response. In addition, there is a known association between low levels of vitamin D and diabetes. It is possible that this may not result from the lack of vita-min D itself, but from other factors somehow related to low vitamin D levels. Replenishment of vitamin D has not been shown to prevent diabetes long term and it is too early to draw conclusions about this.