How much water should we drink a day? You might have been told, “you must have 2 litres of water a day for optimal health”. Well, if you believe that, I’m sorry to burst your bubble – there is not one shred of evidence to support that as a guideline.

Two important points:

  • Everyone is different – the fluid requirement for a 50 kg female is very different from that of a 100 kg male.
  • Food provides fluid, particularly if you have a diet rich in fruit and vegetables – that can provide up to 3 cups of total fluid across the day.

Interestingly, while caffeinated drinks have been shown to cause diuresis (causing you to urinate more) the reality is that if you stay attuned to it, and just drink a bit more water, tea and coffee doesn’t have to become a problem for people, unless you are a total ‘tea and coffee monster’.


You need to be aware of your own symptoms of hydration.


How do you know if you’re a caffeine monster? You need to monitor your hydration status. If you don’t go to the toilet all day, or only go once; if you have dry lips; a dull headache and you’re struggling to concentrate, I’d be 99% sure that you are dehydrated.



How much fluid should you drink? You need to be aware of your own symptoms of hydration. Enough fluid might be a few glasses of water, a couple of herbal teas, it might one or two coffees during the day, it might be some bone broth or miso soup. Avoid fruit juices and cordials.   


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BBC Future: How much water should you drink a day?

Whether you’ve had fatigue or even dry skin, you’ve probably been told to drink more water as a cure. But this advice comes from decades-old guidance… and may have no scientific basis.

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Dr Caryn Zinn is the lead instructor for the short course PK203: Fasting: The Science and Practice. Professional training in the therapeutic benefits of fasting.