user167: Whenever I play long tournament games, I find that I drink simply enormous amounts of water, far more than my typical rate in daily life (and maybe even more than when I am unusually physically active). I don't do this deliberately, or with any purpose in mind; it just seems that my body desperately seeks hydration when I play chess. I know that some famous players swear by particular drinks during games, e.g. Boris Gelfand during his recent match with Anand talked about an energy drink that he always has in his thermos, and Magnus Carlsen seems to keep plenty of OJ around:

More generally, what I'd like to get here is this:

Pointers to any studies concerning the advantages or disadvantages of the consumption of particular foods or drinks during sustained, concentrated mental activities or competitions like chess (but not necessarily chess).

One interesting read I stumbled on is FM Mike Klein's article "The Grandmaster Diet," which references some scholarly studies related to this matter, as well as items such as a survey by Roberto Baglione of the nutritional habits of 72 GMs and WGMs, which includes anecdotes like the following:

"[GM John Fedorowicz] won’t eat a meal if he cannot complete it at least two hours before a game (according to Fedorowicz, GM Walter Browne used to advertise a free steak dinner to his opponent, with the caveat it had to be eaten right before the round). ... Fedorowicz almost always shuns food during games as well, though he did confess to eating a piece of cheese during a seven-hour round at a U.S. Championship several years ago.

I'd appreciate pointers to any other reliable sources that touch on this general topic of food and drink consumption during activities like chess.

user307: Here is an article I came across a while ago.
This is probably the key part:

Chess players should try to have breakfast daily.
Avoiding “heavy foods” or foods of difficult digestion before games
  must be adopted as a regular habit for chess players. The last “main”
  meal before a game has to be had at least three hours in advance. If a
  player wishes to have something to eat nearer the time of the
  beginning of a competition (one or two hours before, e.g.) he/she
  should choose among fruits (whole ones, fruit salad or juices,
  raisins), cereal bars, pretzels, cookies, low fat yogurt with fruit or
  cereals, sports drinks.
During the games, it is recommended fluid ingestion, and, if the chess
  player wants it (or when the game becomes long), solid foods. Mineral
  water, fruit juices, tea, coffee, sports drinks, cereal bars, fruits,
  raisins, dry fruits (almonds, e.g.), chocolate, cereal cookies, can be
  chosen. In all cases, moderate quantities should be taken.
The best strategy to hydration is to drink small quantities at regular
  intervals, instead of greater quantities at a few intervals, and avoid
  being thirsty. The same indication should be followed during board
  training and physical activity. It is also important to begin the
  activity properly hydrated.


user394: One of the problems is that in the human body, the thirst and hunger mechanisms are not always clearly defined, so that when you are hungry you can feel thirsty, and vice versa. I would posit that you are likely low on circulating glucose, and mistaking hunger for thirst.
The brain uses up vast amounts of glucose while kicking over, and while there haven't been any physical studies of the amounts used during concentration (at least not that I can find in humans, there are some in rats), it is known that higher concentration uses more glucose.
There have been numerous studies that show meal composition and timing have an effect on both mental and physical performance, with breakfast being an important component. Here are a couple of those studies (one for physical, one for mental):
Cognitive Performance
Physical Performance
I recall seeing a study that suggests sweet taste (such as hard candy, etc.) can also trigger the body to release extra glycogen, but I don't recall where. 
I would suggest that eating a balanced, healthy breakfast the day of matches, and mild snacking throughout the day (Other studies have shown that mental performance can be impaired immediately after meals - which is likely where the GM interview from the study you cite comes from) will help keep your body well supplied. 
I generally suck on hard candy, or (since I also do endurance athletics) I have something like a GU gel or soft chew, which is basically quickly digestible, 100 calorie foods that help fuel the body during performance. You can find various types (Gels, soft chews, drink mixes) at most cycling/endurance stores (REI, multi sport stores, etc.)
Experiment a bit and find what works best for you, each individual is different. I would suggest that high sugar drinks (such as orange juice, etc.) are ok if you don't gulp it and are done, but rather sip throughout. Otherwise you provoke other responses in the body that result in glucose spikes and dips, which won't help.

167: <p>Whenever I play long tournament games, I find that I drink simply enormous amounts of water, far more than my typical rate in daily life (and maybe even more than when I am unusually physically active). I don't do this deliberately, or with any purpose in mind; it just seems that my body desperately seeks hydration when I play chess. I know that some famous players swear by particular drinks during games, e.g. Boris Gelfand during his recent match with Anand talked about an energy drink that he always has in his thermos, and Magnus Carlsen seems to keep plenty of OJ around:</p>

<p><img src="https://i.stack.imgur.com/faSxZ.jpg" alt="Carlsen OJ"></p>

<p>More generally, what I'd like to get here is this:</p>

<blockquote>
  <p>Pointers to any studies concerning the advantages or disadvantages of the consumption of particular foods or drinks during sustained, concentrated mental activities or competitions like chess (but not necessarily chess).</p>
</blockquote>

<p>One interesting read I stumbled on is FM Mike Klein's article <a href="http://chess.jliptrap.us/grandmasterdiet.htm" rel="noreferrer">"The Grandmaster Diet,"</a> which references some scholarly studies related to this matter, as well as items such as a survey by Roberto Baglione of the nutritional habits of 72 GMs and WGMs, which includes anecdotes like the following:</p>

<blockquote>
  <p>"[GM John Fedorowicz] won’t eat a meal if he cannot complete it at least two hours before a game (according to Fedorowicz, GM Walter Browne used to advertise a free steak dinner to his opponent, with the caveat it had to be eaten right before the round). ... Fedorowicz almost always shuns food during games as well, though he did confess to eating a piece of cheese during a seven-hour round at a U.S. Championship several years ago.</p>
</blockquote>

<p>I'd appreciate pointers to any other reliable sources that touch on this general topic of food and drink consumption <em>during</em> activities like chess.</p>
 307: <p><a href="http://www.chessbase.com/newsdetail.asp?newsid=4335">Here</a> is an article I came across a while ago.</p>

<p>This is probably the key part:</p>

<blockquote>
  <p>Chess players should try to have breakfast daily.</p>
  
  <p>Avoiding “heavy foods” or foods of difficult digestion before games
  must be adopted as a regular habit for chess players. The last “main”
  meal before a game has to be had at least three hours in advance. If a
  player wishes to have something to eat nearer the time of the
  beginning of a competition (one or two hours before, e.g.) he/she
  should choose among fruits (whole ones, fruit salad or juices,
  raisins), cereal bars, pretzels, cookies, low fat yogurt with fruit or
  cereals, sports drinks.</p>
  
  <p>During the games, it is recommended fluid ingestion, and, if the chess
  player wants it (or when the game becomes long), solid foods. Mineral
  water, fruit juices, tea, coffee, sports drinks, cereal bars, fruits,
  raisins, dry fruits (almonds, e.g.), chocolate, cereal cookies, can be
  chosen. In all cases, moderate quantities should be taken.</p>
  
  <p>The best strategy to hydration is to drink small quantities at regular
  intervals, instead of greater quantities at a few intervals, and avoid
  being thirsty. The same indication should be followed during board
  training and physical activity. It is also important to begin the
  activity properly hydrated.</p>
</blockquote>
 394: <p>One of the problems is that in the human body, the thirst and hunger mechanisms are not always clearly defined, so that when you are hungry you can feel thirsty, and vice versa. I would posit that you are likely low on circulating glucose, and mistaking hunger for thirst.</p>

<p>The brain uses up vast amounts of glucose while kicking over, and while there haven't been any physical studies of the amounts used during concentration (at least not that I can find in humans, there are some in rats), it is known that higher concentration uses more glucose.</p>

<p>There have been numerous studies that show meal composition and timing have an effect on both mental and physical performance, with breakfast being an important component. Here are a couple of those studies (one for physical, one for mental):</p>

<p><a href="http://informahealthcare.com/doi/abs/10.3109/09637489709006958">Cognitive Performance</a></p>

<p><a href="http://www.jappl.org/content/84/1/53.short">Physical Performance</a></p>

<p>I recall seeing a study that suggests sweet taste (such as hard candy, etc.) can also trigger the body to release extra glycogen, but I don't recall where. </p>

<p>I would suggest that eating a balanced, healthy breakfast the day of matches, and mild snacking throughout the day (Other studies have shown that mental performance can be impaired immediately after meals - which is likely where the GM interview from the study you cite comes from) will help keep your body well supplied. </p>

<p>I generally suck on hard candy, or (since I also do endurance athletics) I have something like a GU gel or soft chew, which is basically quickly digestible, 100 calorie foods that help fuel the body during performance. You can find various types (Gels, soft chews, drink mixes) at most cycling/endurance stores (REI, multi sport stores, etc.)</p>

<p>Experiment a bit and find what works best for you, each individual is different. I would suggest that high sugar drinks (such as orange juice, etc.) are ok if you don't gulp it and are done, but rather sip throughout. Otherwise you provoke other responses in the body that result in glucose spikes and dips, which won't help.</p>
