So for the past few years, I have noticed that if I drink decaffeinated diet soda (caffeine can make me crash), I will experience more mind clarity and alertness, with no side effects and no crashing. It won't get me out of a deep crash, but if I am mildly tired and foggy, it will pick me up. Who knew? The mystery ingredient? I believe it to be Phenylalanine, found in the sweetener aspartame, though it could be something else associated with the aspartame. I am sure those of you more schooled in biochemistry could explain why this is so, or why some of us may be deficient in this amino acid. For me, though, it is just another (inexpensive!) weapon in my growing arsenal of supplements to ward off fatigue. I don't drink more than a small glass or two at a time, and it wears off in less than an hour. Of course you shouldn't ingest phenylalanine if you have the genetic disorder phenylketoneuria (PKU), that is unless you like having seizures, brain damage and mental retardation. Of course, if you have PKU, you'd probably know it by now, as it seems pretty unforgiving, kind of like another 3-letter acronym I can think of. http://www.mayoclinic.com/health/phenylalanine/AN01552 I'm sure this is just one more of those things that works for some CFS/ME subsets and not others. Anyone have a similar experience?