While your body requires a pretty constant supply of glucose (i.e., blood sugar) in order to function properly, constantly eating refined sugars and slurping down sodas is not the best way to maintain healthy glucose levels. On the contrary, re- searchers at the Salk Institute in California found that high glucose levels resulting from quick, easily digested sugars slowly but surely damage cells everywhere in the body, especially in the brain. In addition to the unneeded extra calories that these sources of refined sugar provide, sugar can also depress your immune system, de- press your mood, and lead to feeling fatigued.