Water

Contents

• So what does your body do with all that water?
• How to replace water
• Here are some of your questions
• Dr Kim says

Did you know that water is even more important than food to your body because - your body is mostly water?

Yes it's true!

More than half of your body weight is water. Your body can't survive for more than a few hours without it, even less if you live in a hot country or the weather is hot. This doesn't mean that your body is like a glass that you fill with water. Your feet would get pretty soggy wouldn't they?

What it does mean is that water is the biggest part of all the fluids that travel round your body, and there is a lot of water inside your cells too. Even bones have a lot of water in them!

So what does your body do with all that water?

It circulates as blood around all your body - most of your blood is water - and water is also in lymph which travels around your body.

		Blood and lymph are the main ways the body gets food and oxygen to your cells and the way wastes get taken away - this is a very important job for water!! Blood and lymph also have special cells in them which fight infections - they are part of your 'immune system'.
		Water carries digestive enzymes (say dy-jest-iv enz-eye-mz) around your digestive system, so that your food can be broken up into all the bits your body needs.

	All the stuff the body doesn't need has to get out of the body somehow. Some of it goes from the blood to the kidneys, which make urine (wee) - which is mostly water. Some stays in your gut and comes out as faeces (poo) - which is also mostly water! Some comes out in the air you breathe (if you breathe onto a really cold mirror you will see little drops of water on the glass - this is water from your breath).
	You also use water to keep your body temperature even, at about 37ºC.
	Water comes out through the tiny holes in your skin called pores. This water we call perspiration or sweat and it helps to cool our bodies.

	Water is in the fluids that keep your joints moving smoothly [like knees and elbows] so that your bones don't creak and groan like a rusty swing.
	Saliva, or spit as we usually call it, is mostly water. We know when we need more water because our mouth feels dry.
	Mucus is also mostly water. That's the stuff that you see too much of when you've got a runny nose! But mucus is very important, as it keeps eyes, ears, noses, throats and all your inside bits smooth and slippery so that everything can run around all your body systems without getting stuck!

Now that you can see how important water is, you can understand why your body needs so much of it.

Adult bodies use up around 2 litres a day and smaller bodies use less. If you are around 8 years old you might use up about 1 litre a day, so you have to replace that much water.

How to replace water

	You will get some of that water from the foods you eat [like tomatoes, salad and vegetables] but you will still need to drink water as well.
	Try to drink around 6 cups of water a day, more if it's hot, or you've been running around a lot, or you feel thirsty. Of course, you can drink other drinks like milk and juice - they are mostly made of water anyway.
	Be careful with some fizzy drinks. They have water in them, but some of them have lots of sugar too [remember you don't need much sugar].
	Some drinks, like cola drinks or coffee have caffeine in them. Look to see if caffeine is on the list of what's in your drink. Caffeine is a diuretic, which means it will make your kidneys make a lot more urine and you will have to go to the toilet and you will lose all that water again!

If you're really into sport, you can get more information about what to drink and eat in our topic 'Food - eating and sport'.

Here are some of your questions

	Some water can have germs in it, so it is important to be sure that the water you drink is safe. If you are not sure it is safe, make sure the water is boiled before you drink it (or clean your teeth with it). Water that comes from lakes or rivers sometimes has a lot of germs in it, and it needs to be treated before it is used for drinking.
	Most tap water in cities and towns in countries like Australia is safe.

Chemicals like chlorine may be added to the water to kill the germs. The amount of chlorine in water will not harm you, but it may make the water smell different.

Tap water in many countries now has fluoride added to it. Fluoride helps prevent tooth decay. The amount of fluoride added to the water supply does not cause any problems, but if you swallow a lot of toothpaste which also has fluoride in it there can be some problems (spit your toothpaste out after you've cleaned your teeth!!).

A lot of people have started to drink spring water, which has different minerals in it. The water can taste different from tap water so people may like it more. Spring water should be tested before it is sold to make sure there are no germs that could make people ill. Some spring water is very expensive to buy in bottles, but if you are travelling to other countries where the water may not be clean, it is a good idea to use bottled water or boil the tap or well water very carefully. You don't want to get sick while you're on holiday, do you?

Mineral water has become very popular as a mixer with fruit juice. If you are buying a ready-mixed drink, check out how much sugar is in there, as it may not be as healthy as it seems.

Which drinks have caffeine in them?

	Coffee and tea both have caffeine in them and so do chocolate drinks.
	Some fizzy drinks, especially cola drinks, do too, so you need to check the labels to see what's in there. As well as being a 'diuretic' (it makes your kidneys make more urine or wee) caffeine can make people feel different. Some people feel more wide-awake, while others feel shaky and anxious.
	It is best not to have too much caffeine.
Why does salty water come out of your eyes when you cry?

	We really don't know why people make tears when they cry, but tears are made from blood. Blood has salt in it, so tears do too.
If you have a question about water, click the 'Feedback' button, write your question and send it to us.

You don't slosh when you walk, Or burble when you talk, But most of you is water. You leak it through your skin If you're fat or if you're thin, Stay cool, most of you is really water! BH

Dr Kim says:

Use water on the outside of your body too, to keep yourself clean and healthy.

We've collected this information to help you to understand important things about staying healthy and happy. However, if you feel sick or unhappy, it is important to tell your mum or dad, a teacher or another grown-up.