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How much Water should you Drink per Day

We’re all aware of the impact the food we eat can have on our health, but many of us overlook our liquid intake. If we do think about it at all, it’s usually in terms of “how much water should I drink per day?”

You’ve probably seen or heard advice that says you need to drink 2 litres or 8 glasses of water a day, but there is no scientific basis for this arbitrary amount. Yet we all need to drink to avoid major health problems, including dehydration. Just how much do you need to drink, though, and how much of it should be water?

Obviously, high levels of alcoholic drinks have immediate and long term side effects. Most of us are aware of the damage both sweetened and diet fizzy drinks can have on our teeth and digestive systems. The health benefits or consequences of tea, coffee, milk, fruit juices etc are all open to debate and the subject of much discussion.

Just how much do you really need to drink on a daily basis to remain healthy?

The often quoted answer is, as already stated, 2 litres or 8 glasses of water a day. But that’s a generic response that doesn’t take personal circumstances into account. In reality the amount you need will be relative to your weight, diet, location and exercise habits. The amount you need will fluctuate from day to day, largely due to weather and differences in levels of activity. Basically, you need to replace what you lose, through sweating, breathing and excretion in urine and bowel movements and since that differs from day to day, so will your intake requirements.

Some people dismiss the importance of liquid intake, suggesting the average human should be able to consume most of the water intake required from their daily food intake, and advise simply to “drink to thirst.” However, most scientific research seems to suggest that as little as 20% of the liquid required is actually consumed in food, and that by the time you feel the dry throat that is considered the first sign of thirst by many, you may already be mildly dehydrated, and spending any large portion of your life in this state can lead to unnecessary headaches and fatigue.

Two good site that clarify your needs and help you work out how much liquid you need to drink on a daily basis are The Mayo Clinic, and The Water Calculator. The Mayo Clinic explains the different ways of working out how much liquid you might need, and factors that influence that, and the water calculator allows you to enter your weight, atmospheric conditions and exercise level and gives you a personalised rough guide based on that.

What should you be drinking?

Once you have a good idea of how much liquid you need, you are then faced with the question of what you should be drinking to constitute that amount. Recommendations range from discounting all liquid other than water (but how can you be sure of the mineral content etc and do you really want to contribute that much to the plastic mountain, even if you can stomach so much plain water?) to the everything counts philosophy that says even diuretics like tea, coffee and alcohol count since the diuretic effect is less than the liquid intake and therefore the outcome is still an addition rather than a loss of liquid.

Sadly, the honest answer is a resounding “we don’t really know” followed by the sentiment that if you’re sensible and limit alcohol, tea, coffee, fruit juices and fizzy drinks “you should be OK.”

By that reckoning, if your requirement is 2.5 litres, or 11 glasses a day and you drink two units of alcohol a day, three cups of tea a day, one glass of fruit juice and two fizzy drinks, you should still drink three glasses of water on top of this.