Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Caffeine II

In Caffeine I [ For more on 'Caffeine I' go here: http://www.braingle.com/mind/174.html ], we talked about what caffeine is and how it works on the mind. In addition to working as a brain stimulant, caffeine has also been shown to improve athletic performance and endurance.

Two additional things to keep in mind about caffeine are that it is a diuretic and it causes increased calcium loss. So, if you consume caffeine, you should make sure that you are drinking enough water to avoid dehydration and that you are getting enough calcium in your diet.

It's probably a good idea to limit your caffeine intake to 250mg per day (less if you are pregnant). Unfortunately, companies rarely label their products with the amount of caffeine that they contain. Here is a little chart to help you.

Drip Coffee (8oz)95mgInstant Coffee (8oz)85mgDecaf Coffee (8oz)3mgEspresso (1oz)40mgCoffee Ice Cream (1 cup)50mgBrewed Tea (8oz)50mgInstant Tea (8oz)28mgIced Tea (8oz)25mgSnapple Tea42mgCocoa (8oz)6mgChocolate Milk (8oz)5mgChocolate Bar10mgMountain Dew56mgDiet Coke47mgCoke35mgPepsi38mgBarq's Root Beer23mgNoDoz Max Strength200mgNoDoz Regular Strength100mg
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For more mind exercises: http://www.braingle.com/mind/