While too little blood sugar appears to contribute to Alzheimer's, too much - as in diabetes - also brings on degeneration of the brain: "This research used imaging in both human volunteers and in animal models to help us better understand the basic mechanisms behind hippocampal dysfunction in the aged ... The research found that decreasing activity in the dentate gyrus only correlated with levels of blood glucose. ... Beyond the obvious conclusion that preventing late-life disease would benefit the aging hippocampus, our findings suggest that maintaining blood sugar levels, even in the absence of diabetes, could help maintain aspects of cognitive health. ... By improving glucose metabolism, physical exercise also reduces blood glucose. It is therefore possible that the cognitive enhancing effects of physical exercise are mediated, at least in part, by the beneficial effect of lower glucose on the dentate gyrus. Whether with physical exercise, diet or through the development of potential pharmacological interventions, our research suggests that improving glucose metabolism could be a clinically viable approach for improving the cognitive slide that occurs in many of us as we age."