Why does coffee make you dehydrated when the base ingredient is water, yet drinking water on its own afterwards does the opposite?
In: Chemistry
[deleted]
Caffeine dehydrates you and coffee has more caffeine than water so coffee isn’t the best hydrator however if it’s all you had available to you it’s much better than nothing. People will say not to drink coffee how to combat alcohol poisoning because coffee dehydrates you but in reality since it is mostly water it’s still better than nothing. Water is the best bet in most situations but if coffee is what you have, drink it.
This is a misconception. Yes, caffeine is a diuretic, but the effect isn’t strong enough to compensate for all the water in the coffee, unless you’re drinking it super strong.
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).
Your kidney produce around 200 litres of urine every day, but your body just absorbs most of it, and only a bit actually enters your bladder. There’s certain substances, such as beer, apple juice or coffee that mess with this absorbtion process, which means your bladder gets filled with more liquid/you pee out more than you actually drank, and thus you dehydrate
Water in and of itself is net dehydrating. The electrolytes naturally in water and through our dietary consumption are what allow us to rehydrate our cells. The electrolytes hold onto the water.
Coffee makes you pee, and it also might make you sweat due to a combination of it being hot itself, and a stimulant that increases cardiovascular or muscular activity
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