My whole life I was always told this. Even today I probably take in about 8-10 glasses of liquid a day excluding that which comes from my meals.
It causes me to have to wake up in the middle of the night and irritates me.
But experts now warn drinking too much fluid is unnecessary and could actually be harmful.
Not only can it lead to kidney problems, but it can also trigger something particularly embarrassing – excessive sweating.
Professor Mark Whiteley, a consultant vascular Surgeon at The Whiteley Clinic, London, is one of the leading experts in the condition, known medically as hyperhidrosis.
Hundreds of patients visit him each year suffering so badly they are considering surgery to remove their sweat glands.
But in many cases, they are simply drinking way too much fluid.
‘In fact, the first and most important thing I ask them is how much water they consume,’ he told MailOnline.
He said: ‘Lots of advertisers advertise water, and say you have to drink two or three litres a day.
‘That’s medically incorrect.
‘If you go to intensive care you will be but on 1.5 litres of fluid per 24 hours,’ he explained.
‘If a doctor came along and gave you 2 litres, you’d get heart failure and they’d be sacked.’
Around half a litre of fluid is metabolised from food every day, and most people drink tea and coffee on top of that intake.
‘You don’t need much extra,’ Professor Whiteley said.
‘If you drink more, your kidneys have to work extra hard to get rid of this fluid load.
‘Then you sweat it out, which makes people sweat even more.
‘There’s this weird idea that if you’re drinking too much and sweating, you need to drink more.
‘People should be saying “Drink if you’re thirsty”. Urine should be yellowish, clear.’
His warning comes after a paper published in the British Medical Journal said NHS advice to drink six to eight glasses a day is ‘not only nonsense, but thoroughly debunked nonsense’.
The paper’s author, Dr Margaret McCartney, a Glasgow-based GP, said that the benefits of the drink are often exaggerated by ‘organisations with vested interests’ such as bottled water brands.
Dr McCartney also pointed out that research shows drinking when not thirsty can impair concentration, rather than boost it, and separate evidence suggests that chemicals used for disinfection found in bottled water could be bad for your health.
Drinking excessive amounts can also lead to loss of sleep as people have to get up in the night to go to the toilet, and other studies show it can even cause kidney damage, instead of preventing it.
Worryingly, Dr McCartney also warns that taking on too much water can lead to a rare but potentially fatal condition called hyponatraemia, which sees the body’s salt levels drop and can lead to swelling of the brain.
However, Professor Whiteley says there are people who suffer from hyperhidrosis which is not linked to their fluid intake, who will require treatment beyond cutting down on liquids.
It is normal to sweat in heat when exercising, or in stressful situations, he said.
Usually people in these situations sweat all over the body.
But some people are ‘wired differently’ meaning they sweat the same volume, but it is concentrated in one area, usually the armpits or the groin, Professor Whiteley explained.
They may also experience sweating in situations when most people wouldn’t, such as watching television or walking down the street.
‘That’s socially very embarrassing, and so they seek treatment,’ he said.
Hyperhidrosis affects men and women equally, he said, although women find it more of a problem.
It can be caused by stress, a high-protein diet, or some people might react to over the counter medicines and begin to sweat in a certain area of their body.
Professor Whiteley says he advises cutting fluid intake, trying to relax and reduce stress, stopping any over the counter medication that the person has started taking recently and using spray or roll on deodorants for the problem.
If all of these avenues have been exhausted, and the person still has a problem with sweating, he will suggest a treatment such as Botox injections to the armpits, which temporarily stop the sweat glands producing sweat.