https://www.gosh.nhs.uk/conditions-and-treatments/general-health-advice-children/eat-smart/food-science/drinking/
Drinking
You need to drink to keep healthy and keep growing. It helps your
brain and body work properly, as well as your digestion.The amount of
water you need to have depends on your age, weight, how much exercise
you do and how warm it is. You’ll need more in the summer or if the
central heating is blasting out!
So, it’s important to keep drinking throughout the day. But what should you drink? And how much?
Well it’s easy to work out what not to drink! Kids who have lots of sugary drinks (fizzy drinks and squash) are more likely to put on weight and to be overweight.
The best drinks to slurp are water and semi-skimmed milk. These don't contain added sugar that can damage teeth. And milk contains important vitamins and minerals, like calcium.
Fruit juice contains lots of sugar. Eating the whole fruit is often better because then you get the fibre with it. This makes you feel full up. Juice is healthy, but one glass a day is enough. It’s also a good idea to have this at mealtimes for the sake of your teeth. Either this or you can water it down if you like. You can do the same thing with squash. One glass of pure fruit juice counts as one portion of your fruit and vegetables a day. Two glasses does not mean two portions though. This is because you are not getting the fibre.
How much should I drink?
Aim to guzzle 6-8 glasses of fluid per day. Your wee is good at showing if you should be drinking more. If it’s dark yellow then you need to drink more – your wee should be light yellow. Remember to drink more if you are doing exercise. This will stop you from getting dehydrated (when your body does not have enough water).