Is it true that … we should all drink more water?

Sorry Stanley cup devotees, the environmental physiology professor Lewis Halsey at Roehampton University says there has been an “overselling of concerns” about consuming enough H2O.

“It’s a tricky one,” Halsey says. “Obviously people can become dehydrated. We are set up to have quite a high water turnover rate: we sweat it out to keep cool, and we therefore need to recover those fluids. However, we can, at least in the short or even medium term, lose quite a lot of fluids and be fine.”

Halsey, who’s researching sweating and drinking’s impact on body temperature, says the amount of water each person needs is variable. Bigger, more active people generally need more. If someone has very low body fat levels – either because they’re very slim or very muscular – they also need more water because muscle holds more water than fat, so more of their body tissue needs keeping hydrated. Those who live in a less humid climate may need more, as “they lose more water on their breath”. And because 20-30% of our water intake comes from food, if your diet is made up of more calorie-dense foods you may also need to drink more. “Part of the reason the food will be high density is because it’s low in water,” Halsey adds.

So, how do we know if we’re drinking enough? “Drink when you’re thirsty,” Halsey says, rather than aiming to hit a certain target. His one exception is elderly people: “Typically, they have a reduced sensation of thirst, and so they’re more vulnerable to chronic dehydration.”

One thing he says we all definitely shouldn’t feel obliged to do is constantly sip water throughout the day. “The body is absolutely fine at dealing with intermittent bursts of water ingestion,” Halsey says.

In fact, at rest, drinking more than a litre an hour can be harmful. Step away from that new bottle the size of your head.