Dehydrated? Drink Coffee.

By Joelle Renstrom | Published

coffeeThanks for legitimizing my vices, science! In addition to showing that alcohol consumption can be good for us by boosting the immune system’s response to vaccines, among other things, a new study from England’s University of Birmingham suggests drinking coffee will keep us as hydrated as drinking water. Hang on a second while I get myself a second cup of Joe, and then I’ll tell you the details.

We’ve all heard for so long that there’s no substitute to water when it comes to what our bodies need, and by and large, that seems to be true. Other drinks have been vilified (some probably rightly so), downsized, and generally discouraged. But coffee isn’t a high-fructose-corn-syrup-infused bomb (unless you do really weird things to your java), and we’ve all made it by pouring a bunch of water into a coffee maker — so why wouldn’t it be hydrating?

Coffee gets categorized with tea and other caffeinated beverages because it makes us pee. A lot. Coffee was deemed a diuretic way back in 1928, and since then we’ve pretty much accepted that any drink that makes us pee so much can’t possibly be hydrating and is likely dehydrating. The Birmingham researchers, who perhaps are the rare Brits who prefer coffee to tea, wanted to challenge that status quo, so they designed a study to test whether “regular” coffee consumption affects the body differently than drinking water. Using 50 men (apparently women’s menstrual cycles affect their hydration levels enough to throw off the results) who regularly consume coffee and weren’t on diuretics or medications that contain caffeine, the researchers initiated phase one of the study, in which the subjects drank either four cups of black coffee or four cups of water each day for three days. They measured and analyzed the hydration of the subjects via blood tests, urine tests, body mass, and total body water content. Then, after 10 days of resuming normal drinking habits, the two groups switched, the coffee drinkers now guzzling water and vice versa.

Ultimately, the researchers didn’t find a significant difference in the hydration levels of the two groups. One thing they did find, though, was that subjects in both phases lost about .2% of their body mass. The researchers think this is because the men weren’t properly hydrated while in the study — that four cups of any liquid isn’t enough for proper hydration. People who are clinically dehydrated will lose 1-3% of their total body mass. Still, the researchers believe that the general recommendations to avoid caffeine or drink a cup of water for every cup of coffee or other caffeinated beverage are obsolete and should be updated.

I think this is a perfect opportunity, especially for us writers. We can get a robot to make us coffee all day long, and then at night we can switch to drinking moon dust beer, which science has helpfully shown to also be just as hydrating as water. Raise a glass to science!