
Have you often wondered: how much water should I drink in a day, and been told it should be 8 glasses/2 litres at least?
But is that actually true, and what is the basis for it?
In 2007 the peer reviewed British Medical Journal included the: drinking 8 glasses of water a day ‘rule’ as the first entry in its list of ‘medical myths’.
The 8 glasses of water a day advise first came in 1945 when the US Food and Nutrition Board stated that the average adult body needs over 2 litres of water a day. Then, just two sentences later, the board said that most of this water allowance would be met through what you eat and drink anyway.
Somehow, that last sentence of advise has got lost over time, with people only remembering they ‘should’ drink 8 glasses of water extra, each and every day.
Water is present in fruit, vegetables, prepared foods like curries, stews, soups and more, as well as your daily cups of tea and coffee – and maybe even a beer or two on occasion!
There is no scientific evidence to support that you need an extra 8 glasses of water a day, on top of what you consume normally.
In fact, a study done in another prestigious science journal PNAS (Proceedings of the National Academy of Sciences of the United States of America) found that once you have satisfied your thirst, continuing to drink could actually become unpleasant.
It depends.
A few things must be taken into account:
Sometimes you will need to drink more, sometimes less. Most people can stay healthy by just drinking water when they feel thirsty.
If you’re thirsty, go ahead and drink some water, and if you’re not, that’s fine. One of the key authors from the PNAS study concluded:
“If we just do what our body demands us to we’ll probably get it right – just drink according to thirst rather than an elaborate schedule.” Associate Professor Michael Farrell
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Written by Paul Taylor
Paul Taylor is a New Zealand–based healthcare content writer with 5+ years’ experience creating patient friendly articles for online pharmacies and health platforms. He specialises in accessible condition guides, prescription FAQs, OTC advice, and health & wellbeing tips, translating complex medicines or health condition information into clear, actionable content. Paul collaborates with the ZOOM Pharmacy clinical team and bases every article on authoritative sources, peer reviewed journals and national clinical guidelines to ensure evidence based, up to date content. His goal is to help readers feel empowered to make informed decisions about their medicines and wellbeing. This content is general information only and does not replace professional medical advice.