I tried something called Alpha-Brain by Onnit Labs based in Austin. The main ingredients of which are tyrosine, theanine and a bunch of other stuff. It is marketed as improving focus/memory.

I used it for a couple of weeks and saw no benefits. The only noticeable change was my dreams got vivid when taking it (which is also claimed by them). When taking it, I also had short episode that felt like onset of a sudden dementia, I could not remember anything. Example: I couldnt remember where my car was parked when I was standing right in front of it. I dont know if it is caused by Alpha-Brain, but I was not taking anything else during that period. I stopped taking it soon after.

Like they say, there is no biological free lunch. I would say the safest way is probably good nutrition, enough sleep and exercise.