Hydration advice attracts mysticism like nothing else in nutrition — mineral timings, gallon challenges, apps that shame you hourly. The actual reference document is refreshingly dull.
The reference numbers
EFSA’s adequate intake for total water is 2.0 litres a day for adult women and 2.5 litres for adult men, under moderate temperatures and moderate activity.
The key word is total. The figure counts drinking water, every other beverage — coffee and tea included — and the water inside food. Soup counts. Yogurt counts. A tomato is mostly water and it counts too. Food typically contributes a meaningful slice of the day’s total, which is why “I must drink 2.5 litres of plain water on top of everything” is a misreading of the number.
About the eight glasses
The famous 8×250 ml rule isn’t the EFSA figure and never had a clear source — it survives because it’s easy to remember, and it lands in a similar region by accident. Harmless as a habit; not a law.
The boring, reliable signals
For healthy adults in ordinary conditions, the body’s own signalling does most of the regulation:
- Thirst works. It’s not a crisis alarm that fires too late — it’s the routine signal, and answering it is the system working as designed.
- Urine colour is the free dashboard: pale straw suggests you’re fine; consistently dark suggests drinking more.
Heat, long exercise, illness and some medical situations genuinely change the arithmetic — that’s where personalised advice belongs, and where a lifestyle article politely stops.
The practical reading
Keep water within reach, drink when thirsty, let meals contribute their share, and glance at the dashboard occasionally. Hydration is one of the few areas of nutrition where the boring answer and the correct answer are the same sentence.