As a member of a morning radio show team, I live on coffee.  There have been many days I probably would've fallen asleep at the microphone without it.  But sometimes I get these awful headaches on days when I don't drink my usual 7 pots of coffee.  

Science has answered that problem for me.

According to an article in Food and Wine (which you can find below), caffeine sticks to the receptors in your brain, taking the place of a neurotransmitter called adenosine, which typically keeps you calm.  Caffeine does the opposite.

Your brain doesn't know what's going on, so it tries to overcompensate by creating extra adenosine.  So, if you're an avid coffee drinker and you decide to quit cold turkey, you will feel the side effects.  Extra adenosine means a stronger desire to sleep, and gives coffee addicts that familiar throbbing headache.

Drinking coffee can be good for your health.  But if you decide to quit, the best way is to slowly wean yourself off.