Just curious... Some people say
8 glasses of water but some say that is too much and can result in overhydration. How many liters of water should a 16-years-old teenager (boy) drink a day?
closed as off topic by Matt Chan♦ Mar 30 '12 at 12:41
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Let me start by saying that no amount of water will keep the doctor away. There're still many things that can go wrong.
The 8 glasses of water is not backed up by any meaningful scientific evidence, it's just a rule of thumb. But it includes water from all sources including food.
There're two different things that are referred to as dehydration. Acute and Cronic.
You asked about overhydration. It's not the total volume/day that can cause problems but the volume/hour. Healthy kidneys can deal with about a liter of water in an hour. The bottom line is that your body can easily deal with processing 6 liters of water if spread throughout the day but could struggle with 2 liters of consumed in an hour.
It would be a good idea to monitor salt intake. You see the body requires only 3 to 5 grams of salt a day to stay healthy, but most people gobble up 12 to 15 grams of the stuff daily. To rid itself of the overload, the body requires copious amounts of liquid.