B12 vitamin. That's one supplement that makes my urine almost neon yellow and smelling of chocolate a couple of hours after having taken a pill of it. I have taken B12 on occasion for the energy boost is supposedly gives athletes, but I'm not sure if it ever does much for me. I have not coupled it with B6, though I'm curious to give it a try. Being an aging marathoner (I've run 28 marathons including Boston 6 times to date) who's not quite the runner I was when I started out engaging in the highly addictive sport of distance running 30 years ago, (endorphin highs, you know) I'm always trying to find that magic pill that will enable me to recapture the running days of my younger years, that is, be able to run the distances I used to run, at the same pace, and without the achy knees. I'm afraid I'll never find such a magic pill. Seems a 200 mg tablet of caffeine is the best thing I've found so far to (somewhat) reclaim my youthful running days. About the B12. Have you noticed how you can essentially take massive doses of it with evident impunity, it being a water-soluble vitamin? Some of the 2 pill dosages of some B12 tablets have skyhigh RDAs of 10000%.