The 2 Liters of Water Myth: What the Evidence Says
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EFSA recommends 2.5 L (men) and 2.0 L (women) total, not all from water. Coffee, fruit, and vegetables count.
The '8 glasses a day' or '2 liters' rule is probably the most repeated and least supported nutrition recommendation out there.
Where the rule came from
It spread from a 1945 National Research Council recommendation that said: '2.5 L of water for an average adult, much of it already present in prepared foods.' People forgot the second part—and the myth was born.
What EFSA actually recommends
- Adult men: 2.5 L total/day.
- Adult women: 2.0 L total/day.
- This includes water from food (fruits, vegetables, soups: ~20-30% of the total).
- Plain drinks: ~1.5-2.0 L for men, 1.4-1.6 L for women.
Coffee and tea count
Maughan and Griffin's 2003 study debunked the dehydrating coffee myth. Caffeinated beverages still contribute net water to hydration. What doesn't count toward hydration: alcohol (>4% vol is diuretic) and sugary sodas (net positive for hydration, but terrible for your health).
How to know if you're well hydrated
The simplest, most accurate method: urine color. Pale yellow = good. Dark = drink more. Clear = excess. Thirst works too: if you're thirsty, you're already mildly dehydrated, but your body self-regulates.
About this guide
- Last reviewed
- . We review content at least once a year, and sooner if relevant literature comes out. Update policy.
- How it is verified
- We prioritize meta-analyses, systematic reviews and official positions (ISSN, ACSM, EFSA, WHO, Cochrane). Full methodology · topic: Hidratación.
- Conflicts of interest
- Some product links are affiliate links from Amazon España and earn us a small commission at no extra cost to you. How we fund the project.
- Medical disclaimer
- Educational content. Does not replace consultation with a healthcare professional. More detail.
Spotted an error in a formula or recommendation? Email us at jesus.narvaez.tames@hotmail.com. Corrections are published as an updated note on the guide.
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