I have been experimenting with a multitude of supplements, with ethanol, B12 and naturally produced endocrine and neurological chemicals being being my main targets. I've had to take a hiatus from my research, but more details are available here:
In any case, once life permits I will be back into investigating the effects of many endogenous and exogenous supplements on one's chess ability...
I use Beta Blockers all the time when playing OTB. It prevents adrenaline from being released and lowers your heart rate allowing you to relax and really play your A game and not slip up due to tension. Lots of performers etc. use it and it really works.
I used to drink coffee as well to keep my mind focused but now I have hit on a very good system. I start drinking pre-workout sport supplements about two weeks before a tournament. They are loaded with caffeine but also tend to make you very energetic ,making it impossible to sit still. However after about 10 days of constant use this effect starts to wear off and you are left with the benefits of the high caffeine content only,keeping you really sharp.
I have a few more aces up my sleeve but I am wondering what other players use before or during an OTB tournament.
Beta blockers can kill you! Here's what Dr. Mercola says about them:
http://articles.mercola.com/sites/articles/archive/2008/06/07/more-drugs-that-kill-you.aspx
And basically anything Dr Mercola says, you should do the opposite.
http://rationalwiki.org/wiki/Joseph_Mercola
http://www.quackwatch.com/11Ind/mercola.html
http://www.sciencebasedmedicine.org/for-shame-dr-oz/
http://www.skepdic.com/mercola.html
I am not a medical expert despite the Doctor title I have since I am an honorary Doctor of Divinity. But I know what works and what does not work for me. I have been following Dr. Mercola's suggestion to eliminate bread from my diet and I have lost 30 pounds. Many of his other suggestions are also very good. I am especially interested in the articles about water fluoridation that he has on his website. It has been proven that fluorides in water cause cancer yet they keep putting this poison in our drinking water. From my own experience and knowledge I find Dr. Mercola to be right on about most of the things he says and writes about. From my own experiences in life, I have found conventional medicine to be a bust. The alternative medical advice given by Dr. Mercola does indeed work. If you do not choose to follow Dr. Mercola's advice, that is fine with me, but do let me know what kind of flowers you would like me to send to your funeral.