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Girl drinking glass of water

Curious Kids: how do we feel thirsty?

How do we feel thirsty? Shruthi (she), 8 years

Hi Shruti!

Thank you for your important question.

Most of our body is made of water. And we need water to do all sorts of really important things. We need water to help us digest our food, and move nutrients and oxygen around our body. We need water to make our muscles move and to make sure we don’t get too hot or too cold.

We lose water all the time too – when we sweat, breathe and go to the toilet.

So we need to replace that water. If we don’t, we can start to feel thirsty.

Feeling thirsty is good for us

Our brain is amazing. It can tell us when our body doesn’t have enough water (but has too many salts and minerals).

Our brain then sends messages to parts of our body to put things right. We feel those messages as an urge to drink. And when we feel that thirst, we drink.

Read more: Curious Kids: how do sea creatures drink sea water and not get sick?

How do we know when to stop drinking?

We all know that nice feeling once you start gulping down water on a hot day. But how does your brain know you’ve had enough water?

When we drink water, the water levels in our blood rises, and the levels of salts and minerals drop. When your brain is happy with these levels, it tells us. It removes the urge to drink any more.

Also, when we swallow water, a “happy” chemical called dopamine is released into our bodies that makes us feel good. This is why drinking other liquids, like fruit juice, can feel good, even if it doesn’t doesn’t do as good a job as water at rehydrating us.

Feeling thirsty is a sign you need to drink more water. Created in Canva by Roshan Rigby/Author provided

Listen to your body

As the weather gets hotter, it’s even more important to keep drinking water. You want to replace all that water you lose while riding your bike, or running around with your friends in the heat.

So if you feel thirsty, that’s really your brain telling you to drink up.

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