Most of the research underpinning the coffee-as-diuretic idea focuses on the role caffeine plays, and “one of the most frequently mentioned studies was conducted way back in 1928 with a sample of just three people,” says Hammond. Here’s her theory on why people have believed in diuretic effect for so long:
Although we might notice needing the loo more when we’ve been drinking coffee, the mistake is basing our observations on a comparison with the time we’ve drunk nothing, not with a similar amount of water. If you chose a glass of water instead of a cup of tea, you’d probably see the same effect. [BBC]
That doesn’t mean you should necessarily drink eight cups of coffee a day (any more than you need to drink eight cups of water), but you probably shouldn’t fret too much about that daily pot of coffee dehydrating you, either. Click here to check out our coffee range and other health products.