Debunking The ‘8 Glasses of Water a Day’ Myth

Isabelle Laker by Isabelle Laker 9 August 2017

How much water do we really need to drink? Check out the science behind hydration here

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Debunking The ‘8 Glasses of Water a Day’ Myth

In order for our bodies to function properly, we need to drink roughly eight glasses of water each day… right? Wrong. According to scientific authorities, there is no evidence to support this rule. 

Let’s start with the basics of the issue. 

Why we need water

The human body (along with every single other living thing) requires water to survive. In fact, chances are you can’t survive more than three days with it. Water is present in every single chemical reaction in the body and makes up over half its mass. It carries oxygen to our cells and cushions our joints, among a million and one other things.

Our bodies lose water through sweat, digestion and even breathing, so it’s important to replace these fluids. But how much do we actually need?

Woman drinking water

Origins of the myth

Where did the idea that our bodies need eight glasses of water actually come from? Most say that it started because of a report from the US Food and Nutrition Board of the National Research Council way back in 1945. "A suitable allowance for adults is 2.5 litres daily in most instances. Most of this quantity is contained in prepared foods." Conveniently, that second sentence is all but ignored. Our bodies get most of the water they need from the food we eat. Sure, we supplement this with water and other beverages, but by no means do we need to go out of our way and closely monitor how much we’re drinking. 

Are we drinking too much or too little? 

We’re constantly inundated with new studies reporting that we’re dehydrated. The simple fact is most people are not dehydrated. However, having too much or too little water in our bodies is dangerous. 

We know that dehydration is serious, but so too is drinking more water than our bodies can process. It’s called water intoxication, and it’s a result of drinking too much water in a short space of time. In an extreme case, a Californian mother, Jennifer Strange, died from drinking too much water during a radio contest. Obviously, this is an incredibly rare case and not the norm, but it goes to show that there are dangers on both ends of the spectrum. 

Man drinking water

So what do we do?

How do we know when our body needs more water? We get thirsty. It’s a pretty obvious answer. However, when we follow strict health regimes, we can sometimes forget just how finely tuned our bodies are to their needs. Another great indicator is the colour of your urine. Clear or pale yellow means you’re well hydrated, dark yellow indicates you should be drinking more water. 


There’s no exact science to calculate just how much water you should be drinking on any given day. Gender, size, age, environment, health and activity levels all affect how much water we need. The important thing is to listen to your body – it knows what it needs to run itself!  

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