[hntrader]

They do do something. Caffeine is a nootropic that has well studied positive effects.

The thing with most nootropics though is that the effects aren't big, the side effects of chronic usage aren't well known, and the basics such as exercise/sleep have a bigger effect.

Out of the two mentioned above (magnesium and l-theanine) - many people are deficient in magnesium due to modern diet, and there's some evidence that l-theanine works well with caffeine to aid concentration (it's found in green tea but not coffee). I have no idea about the neurogenesis claims though.