It should be noted that excessive coffee swallowing also leads to some pretty serious gastrointestinal problems. A friend of mine had regularly consumed about three pots of coffee a day, for somewhere around 10 years. No surprise really when he developed ulcers and was diagnosed with gastritis. As with anything, indulge in moderation.
:: Oh, and I once read in some extremely obscure but reliable medical journal from the 1920s, that excessive masturbation causes blindness, you might want to watch that. Yet if you are already blind and are reading this via some digital text to braille converter, fap away::