You Don’t Need To Drink Eight Glasses Of Water A Day

The idea that an adult needs to drink eight glasses of water a day is one of the more persistent health concepts you’ll encounter. However, as we’ve pointed out before, it’s almost entirely bogus.

On analysis site the Conversation, Deakin university nutrition professor Tim Crowe thoroughly debunks this idea, pointing out that the amount of water each individual needs will vary depending on “body size, physical activity levels, climate and what types of food [you]are eating” He also emphasises something that lots-of-water proponents often miss: the water that you get from food and from other drinks does contribute to your daily liquid needs. In this context, coffee is nowhere as evil as many people suggest:

The “coffee makes you dehydrated” mantra is another myth that needs to be busted. Drinks such as coffee, tea and cola do have a mild diuretic effect from the caffeine but the water loss caused by this is far less than the amount of fluid consumed in the drink in the first place.

None of which means that drinking water isn’t a good idea, simply that setting an arbitrary target doesn’t make sense. As Crowe points out, the colour of your urine remains the simplest indicator of whether you’re getting enough liquid. If it’s dark, you need more. Hit the link for all the details.

Monday’s medical myth: drink eight glasses of water a day [The Conversation]


  • Generalisations are typically incorrect, even if they were originally based on actual scientific fact. Life typically has too many variables to create hard and fast rules, so trying to do so is pretty dumb. This is no exception. Main flaws with the whole “Eight glasses of water per day” argument:
    – A “glass” isn’t a standard unit of measurement. If you’re drinking pint glasses of water, you’re consuming nearly twice as much as a middy glass (why I’ve used beer glasses as standards of measurement here, probably says something in itself).
    – Different body sizes require different amounts of fluid.
    – The amount of fluid required for your body size will fluctuate on factors such as your metabolism, the surround environment (i.e. temperature), and how active you are on the day.
    – The rate at which you can absorb fluid will be affected by if you’re eating at the same time, and if so, what and how much you eat.

    All of the above also assumes you’re drinking straight water, and doesn’t even take into consideration the fluid content in foods, or other drinks containing minerals other than water.

    It’s not rocket science, if you’re thirsty, drink. If not, don’t.

    Unfortunately, I think health fanatics have adopted the “more is better” mentality, believing that water is good for you, so more is even better. I personally believe in part, that belief has been influence by the fact that excess fluids will disrupt your digestion/metabolism process, causing your body to not fully digest food as it would, and in turn, you lose weight because fat is processed instead.

  • Sorry Sam but it’s not as simple as “if you’re thirsty, drink. If you’re not, don’t”. Thirst is often misinterpreted by the body as hunger. The “* glasses” rule is a simple, effective way to get people to drink water when many of us simply aren’t drinking enough fluids for the type of diet we have. The urine colour factor is making inroads now, but people like routine so I can’t see the harm in setting one that has only benefits and no drawbacks (and I’m assuming people aren’t using 2 litre glasses each time as yes, drinking excessive amounts of water can be harmful).

    • While it’s true that drinking excessive amounts of water can be harmful, it generally isn’t an issue for almost everyone. The amount of water intake needed for harm to be done is quite substantial.

      A healthy kidney can excrete on the order of a litre of water so a person can drink about a litre per hour and not experience a net gain of water. Most people, even those who think they drink a lot of water, don’t drink that much. Obviously it depends on environment, body type and physical activity but I believe the upper limit is between 1-2 litres/hour. There was a woman who died after consuming (and then holding) 6 litres of water in 3 hours for a competition.

  • I always try to drink 2-4 litres a day anyway. You may not need that much to survive, but it’s good to flush the system out and actually makes me feel better anyway…

  • I find if i drink more than 1L of water (or other fluids, such as softdrink) a day i feel less well (but not sickly) than what i would if i went without water at all. I only drink lots of water if i have been doing manual labour or exercise. That being said i eat an awful lot and i have many cups of tea and coffee per day so i probably get a lot of fluids from elsewhere. So i am fairly sure, in my case, there can be too much fluid consumed.
    My girlfriend dislikes how i rarely drink. She drinks about 2-3 litres a day. The odd thing about that is she is very short and very thin where i am quite stocky and medium height. I think there is no one size fits all measure to how much fluid we should consume and rather it is a matter of personal preference.

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