With spring in the air, thoughts turn to marathons, heat - and dehydration. So how much liquid do we need?
If you are confused about how much water we should really be drinking, then you are not alone. I am often asked: is it two litres? Four litres? Does a can of diet cola count?
According to the UK Food Standards Agency, what we need is about six to eight glasses of fluids a day - about 1.2 litres in total. This will help your body to carry out myriad roles, from helping us to keep the body temperature steady and stable to protecting sensitive tissues such as the spine and keeping up water levels in the brain.
What is crucial here, however, is the word “fluid” because, physiologically speaking, this can be from any fluid source including tea, coffee, squashes, juices, diet or standard fizzy drinks and, to a certain extent, alcohol. Many foods provide fluids as well; watermelon provides 185ml (about a small yoghurt pot's worth) of fluid per 200g slice. Even an average 100g banana provides about 75ml of water.
Scientists say that there is no convincing medical research to prove that glugging litres of water on top of these needs will improve the elimination of toxins by your kidneys, improve skin tone or reduce your appetite or the frequency of headaches.
Responding to your body's thirst mechanism is apparently the best way to remain properly hydrated - and this goes for everyone, including those of us embarking on marathons and fun runs. While amateur runners often believe they should drink as much water as possible during long runs, the reality is that too much can in a substantial fraction of runners be dangerous to health and in rare cases, fatal.