I'm a health and fitness nut, so I read a lot of health studies as well as using my own body as a guinea pig. I've discovered a lot of things - for instance, I don't know if using creatine monohydrate leads to more strength gains than using a placebo, but I do know it makes you pee every 15 minutes.
Reading health studies (or even worse, hearing reports of health studies) can be incredibly frustrating as they often appear to be contradictory. Caffeine is good for you. Caffeine is bad for you. Ephedrine and ECA stacks are dangerous. Ephedrine and ECA stacks are effective and safe to use, etc. What to believe?