You've probably heard that water is good for you, but what does it actually do? Here are seven places in your body where water makes a difference, with the facts kept simple.
Brain: about 75% water
Your brain is about 75% water. Even mild dehydration can affect your focus and your mood, which is why a long stretch without a drink can leave you feeling foggy. Sipping regularly through the day helps you stay sharp.
Heart and blood: plasma is about 90% water
Blood plasma, the liquid part of your blood, is about 90% water. It carries oxygen, nutrients and heat around your body. Drinking enough water helps keep your blood volume up, so your circulation can do its job more easily.
Muscles: about 75% water
Muscle tissue is about 75% water. When you're active, staying hydrated supports your strength and stamina and helps you get through a workout without fading early. Drink before, during and after exercise, especially in the heat.
Cooling: sweat keeps your temperature balanced
When you get hot, from the sun or from exercise, you sweat. As sweat evaporates from your skin it carries heat away. That water has to come from somewhere, so drinking enough keeps your body temperature balanced on warm days and active ones.
Kidneys: about 180 litres of blood filtered a day
Your kidneys filter about 180 litres of blood every day, removing waste and extra salt and sending them out in your urine. They need water to do it: drinking enough helps them flush waste away, and pale yellow urine is a simple sign you're on track.
Joints: water helps cushion every move
Water is part of the fluid that cushions and lubricates your joints, helping your bones move smoothly against each other. Staying hydrated is one small way to look after the joints you use every day.
Whole body: about 60% water
Put it all together and about 60% of your body is water. You lose some of it every day through breathing, sweat and trips to the bathroom, so the simplest way to look after everything above is to keep topping it up, little and often.
How much water do you need?
There's no one-size-fits-all answer: it depends on your weight, how active you are and the weather. Our water intake calculator shows how much water to drink a day, in litres and glasses, in a few seconds. Spread it across the day rather than drinking a lot at once, and remember that fruit, vegetables, soup and other drinks count too. If you have a kidney or heart condition, ask your doctor how much is right for you.
This article is general information, not medical advice. If you have a health condition, talk to your doctor.
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