Debunking the Myths of Tea, Coffee, Caffeine, and Dehydration

Everyone knows, or has at least heard of, the importance of keeping hydrated. That’s day 1 human survival stuff, but there’s more to it than you may realize. A widely quoted number suggests needing 8 cups of water a day, but that’s not necessarily the right number for everybody, and some would argue there’s no basis for it. In fact, in some cases, it could be dangerously low.

Common knowledge suggests that our bodies need about two litres of fluid per day, and that’s the “magic number” we’re all taught. Some believe that if you wait until you are thirsty then you are already dehydrated, but others would argue that you should wait until you’re thirsty to drink just as we should wait until we’re hungry to eat or snack.

How much hydration is really enough, and how can you actually achieve this goal?

hydrating with caffeine drinks

At the end of the day, the most compelling argument is that thirst is how your body gauges your water requirements, and so keeping on the right track for water intake is just a matter of listening to your body.

In a balanced diet, most people get about twenty percent of their requirements from their food. Studies indicate that anything you drink counts towards hydration, not just water. All liquids, including sodas and juices contain healthy quantities of water.

Just because the water is mixed with other ingredients doesn’t negate the water’s effects. Your kidneys filter the liquids and extract the water for your body to use. This rings true for coffee and tea, too.

You also shouldn’t worry too much about drinking extra water before exercise, or relying on sports drinks. All you’ll be doing is putting extra liquid in your stomach to slosh around and possibly make you feel quite queasy – or to need to run to the bathroom when you would rather be running that last mile. It is far more effective to make sure that you are drinking adequate amounts about a day and a half before your activity – this allows your body to process and absorb the water properly.

Hydration and Caffeine

The confusion for some people comes when they start thinking about drinks containing caffeine, such as tea and coffee. In recent years, it has become almost an article of faith among some that these drinks actually dehydrate you and cause more harm than good.

Volunteers from The Niall Mellon Township Trust in Africa would disagree with this, having guzzled and astounding 8,000 cups of tea in just four days whilst building a brand-new school for some 1,300 children. It is believed this myth comes from a poor understanding of the nature of caffeine as a diuretic.

Tea and Coffee as a Diuretic?

A diuretic is an effect that forces water to be excreted in urine at a higher rate. The myth that has taken hold therefore is that although cups of tea are made with water, the diuretic effect of the caffeine in the tea means that you could be worse off when considering your hydration levels…

Does coffee hydrate you?

Many people ask “is coffee a diuretic or is it the caffeine”, when in reality the answer is simply put “no.” It’s a lot more complex than just black and white, and for most people, drinking a few cups a day, that’s not a high enough dosage to make a difference.

The problem is that the mechanism by which caffeine dehydrates people only occurs with the consumption of very large doses. A large amount of caffeine in the body is known to increase the blood flow to the kidneys and inhibit the absorption of sodium, which must therefore be passed from the body.

The source of the idea that tea and coffee will dehydrate you dates back to a study done all the way back in 1928, which demonstrated that people who drank caffeinated beverages urinated more frequently, but newer research suggests this original study may have been off-base in some of its conclusions.

“The truth of the matter is, a small increase in urine output has little to do with dehydrating the body,” revealed Lawrence Armstrong, a University of Connecticut professor in the Department of Kinesiology, in a comment to Live Science. “If you drink a liter of water, [urination] will increase,” Armstrong said. “Doesn’t mean you shouldn’t drink water.”

Newer studies looking at more reasonable quantities of caffeine allegedly show a far less dramatic effect, however. By that, we mean that a number of recent studies have shown that the moderate consumption of caffeine in drinks has absolutely no adverse effect on hydration.

Moderate, in this instance, refers to four or five cups of tea a day.

Studies on larger numbers of cups of tea are imminent, to see at what point the higher doses of caffeine start to have an effect, but part of the difficulty of relating these studies to the real world are the huge differences in the way that people drink their tea. Different blends and brands of tea contain different levels of caffeine, people use different amounts of water, and so on.

Not to mention – many people have very different reactions to caffeine, even at different times of tea.

So, what do we take away from all this? Well, most people will point at how they find that they need to go to the toilet more often if they’ve been drinking tea. More recent studies have shown no difference in the amount of times that people need to go to the toilet, or the amount that they go, whether they have been drinking tea, coffee, or plain water. The mistake we make is on basing our observations on a comparison with when we have drunk nothing.

Enjoy your cup of tea, have a snack, and listen to your body. You’re not going to dehydrate any time soon – far from it, you’ve just successfully hydrated yourself.

Some people do seek out diuretic tea, it’s worth pointing out, but that’s because of other ingredients in the tea, not because of the caffeine itself.

But now let’s flip things…

Can you over hydrate with tea and coffee?


This is where it starts to get interesting and more studies would be helpful. The caffeine diuretic effects of these drinks only take hold at much higher doses, but at those higher doses you’re also consuming a lot more water, which can start to lead to the risk of OVER hydration rather than dehydration. You can definitely over hydrate yourself, and that comes back to where this whole article started – listening to your body and being mindful of what it’s telling you. On a really hot day when you’re out and about or exercising, you’ll obviously need more water than on a gloomy day where you’re catching up on the latest season of Rick and Morty.