It is common to see marathon runners or endurance athletes with hyponatremia as they drink a lot of water in an effort to quench their thirst, and the symptoms can be misinterpreted as dehydration. The signs of water intoxication are headaches, fatigue, confusion, nausea, vomiting and drowsiness.

In very rare cases, people have died from drinking an extreme amount of water (three to five litres) within a few hours, due to the pressure it places on their brain.

Fernandez continues: “Your tissue can swell up to some degree; your organs can swell to some degree, your muscles – all of that. But the problem is your brain cannot swell that much – it can only swell to what the skull will allow.”

In California, Jennifer Strange died of acute water intoxication after she drank 7.5 litres on a radio station’s water-drinking competition. The mother-of-three’s family was awarded over $16.5 million (£13m) in compensation after this tragic event, which she entered to win a Nintendo Wii for her children.

The dangers of overhydration and how to avoid it