Water and fluids

You need more fluid than you think on a training day, but less than much advice suggests on an ordinary day.

How much

The European Food Safety Authority's reference intake is about 2 litres a day for women and 2.5 litres for men, everything included. Around a fifth comes from food, so drinking 1.5–2 litres is enough for most people. Per kilo of body weight that is about 30 millilitres – the figure Passboken shows under Food. Coffee and tea count; caffeine does not dehydrate you at normal amounts.

When training

Expect 0.5–1 litre extra per hour of training, more in heat and if you sweat a lot. A simple way to know: weigh yourself before and after a long session – each kilo lost is roughly a litre of fluid. Losing more than two percent of body weight usually shows in performance.

How to tell it is enough

Thirst is a good signal for most people day to day. Pale yellow urine means you are fine, dark means you are behind. Afternoon headache and tiredness are sometimes just too little fluid.

Salt

If you sweat heavily for a long time you also lose salt. On sessions over two hours, in heat, a sports drink or some salt in the meal afterwards can be justified. On an ordinary day nothing extra is needed.

Can you drink too much?

Yes, on very long races. Drinking large amounts of water without salt over several hours can dilute the blood's sodium, which is dangerous. Drink to thirst and replace salt on long races – not "as much as possible".