Why does coffee make you dehydrated when the base ingredient is water, yet drinking water on its own afterwards does the opposite?
In: Chemistry
It doesn’t. Coffee dehydrating you is a myth. The caffeine does negate around 5-10% of the water consumed in that cup of coffee but you would have to take a nearly lethal dose of caffeine for it to negate the total volume of water consumed in that cup of coffee. Your heart would shut down from over stimulation before there was enough caffeine in your system to dehydrate you.
So while you will pee more often with coffee it will not dehydrate you. Alcohol above 20% ABV on the other hand is a potent enough diuretic to cause dehydration. So drinking only spirits will dehydrate you (though most beers will not as they are around 5% ABV).
Latest Answers