It’s a common belief that you must drink at least 8 glasses of water per day. And somewhere, someone would’ve given you the same advice. But have you ever asked yourself, “Who said that?”, and “Why?” and “Does it make sense”?

So, let’s dive straight into it.  First, let’s use the right terminology, because nowhere in your body do you have ‘JUST WATER’.  Ever heard that your body consists of 60% water? That’s not true. Nowhere in your body do you have a single cell that only consists of water. Just imagine, if you weighed 70 kg, that meant 42 kg of you had to be water.  And 42 kg is a big puddle of water which you CANNOT MISS.  You will most likely drown in your own body! What you have in your body, is bodily fluids, like blood, urine with electrolytes and other stuff in these fluids.

Water is important for life.  As humans, we are some of the most water inefficient beings on earth.

Over the course of the day, you will lose water through normal bodily functions, like vapor from your breath, through sweat etc. And you don’t need to live in a warm, humid climate to sweat. Even if you live in Iceland, you will sweat.  And then off course you lose fluid when you urinate.

People loses anything between 1,5 – 2.5 ml of fluid through-out the day. It’s going to happen; it doesn’t matter whether you exercise or not. It also differs from person to person. Every single person is different. 

The notion of 8 glasses of water a day, originates from a 1945 US Food and Nutrition recommendation that you should drink 2.5 L of water per day. 

But here’s the problem with this. It’s just a recommendation.  It’s not based on any research and apparently, most who read this, ignored the following sentence “Most of this quantity is contained in prepared foods”.  Off course we have no idea what “prepared” food really means, but all food contain water, especially vegetables and fruits.  Many fruits contain > 80% fluid, in weight.  So, if you eat a diet of real food, you will easily consume about 2 L of fluid per day

There is another saying going around that says, “Your body doesn’t know when it’s thirsty” OR “If you’re thirsty, it’s already too late and you’re already dehydrated”.  Your body is amazingly designed to let you know what it wants. It will let you know when you’re thirsty, it will let you know when you need to go to the bathroom, it will let you know when you’re hot or cold. Your body have 52 perceptions to help you perceive what’s happening and how it perceives you environment.  Can you remember when you were little, how many times you played outside for hours and forgot to drink or eat something.  If your body couldn’t tell you when you’re thirsty, you would’ve not even made it past childhood, let alone live to read this post. So that doesn’t even make any sense how a child can manage their perceptions of how thirsty they are, but an adult cannot?

So, can you drink too much water?  Yes, you can.

Your blood contains a certain level of sodium that is regulated by your kidneys.  Your kidneys know exactly how to maintain this level in your body and regulates the fluid between the inside and the outside of your cells.

When you drink too much water, you can dilute the sodium content in your blood and when that happens, it cannot fulfill that function anymore. By the nature of how your cells work, fluids will now shift from the outside to the inside of the cell, to the inside. Once the fluid get stuck inside your cells, your cells will start to swell.  Most of your cells can handle that, but your brain cannot, and that’s where it becomes life threatening. When this happens in your brain, your brain starts to swell, and now you have this confined space in your head, where the pressure in your skull increases and all sort of gnarly things can happen that can cause death. This especially happens when you drink massive amounts of water in a short period of time.

So, don’t force yourself to drink litres of water.  Let thirst be your guide.  The average person, working out at the gym, don’t need to drink extra litres of water – just drink when you’re thirsty. The issue with dehydration, especially in endurance sport, is when people are thirsty, and they ignore that perception.  If you’re an athlete, especially an endurance athlete, don’t ignore thirst and drink small amounts of water regularly. 

Take care,