The science is in: Coffee does NOT dehydrate you

Jan 17, 2016

We’ve long been told a cup of coffee dehydrates you.

Even government health recommendations have stated coffee is not appropriate on hot summer days where dehydration is a health risk.

But scientists have now tested this old assumption… and it’s actually not true.

A 2014 study published in the scientific journal PLoS One found that drinking regular quantities of coffee does not dehydrate you. Coffee simply contributes to your daily fluid intake, much in the same manner as tea or water does.

How did they test it?

In this study, 50 male participants were tested in two phases, where they had to drink four cups of either black coffee (200ml) or water per day for three consecutive days.

In the second phase, participants switched drinks to act as the control. So those who drank coffee for the first three days now had to switch to water, and vice versa. This gives the researchers something to compare the first results to.

“We found that consumption of a moderate intake of coffee, 4 cups per day, in regular coffee drinking males, caused no significant differences across a wide range of hydration indicators compared to the consumption of equal amounts of water,” said lead author Sophie Killer.

In other words, 4 coffees per day for three days straight had absolutely no influence on their hydration status.

But coffee makes me race to the toilet?

If you’re first thoughts were along the lines of “hang on, coffee definitely makes me need to pee”, you’re right.

Caffeine on its own is a diuretic (a substance that promoted the production of urine), much the same as alcohol. However, the caffeine you consume in your coffee comes with at least 200ml of water or milk (or both).

Those fluids offset any fluid loss caused by the caffeine. Put another way, it replaces the fluid you are about to expel, and some. So while a pure caffeine pill consumed without any fluid will dehydrate you, a standard cup of coffee (or four) won’t.

We should always drink a lot of water anyways, regardless of the weather, but it is great news for all of us coffee connoisseurs this summer.

I’ll drink to that, will you?

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