TV adventurer Bear Grylls has built a global reputation through his often unconventional and sometimes extreme survival feats to stay hydrated.

He has squeezed moisture from elephant dung, sipped the contents of camel intestines, downed yak eyeball juice and, perhaps most famously, drank his own urine.

If you’ve seen Grylls gulp down a mouthful of his own urine on camera, you might conclude it’s a legitimate survival hack. After all, Grylls used to be in the SAS.

In one episode, he tells viewers urinating on the ground would be wasting fluids, drinking your own urine is “safe”, and grimaces while taking a warm, salty mouthful.

Let’s see if this is fact or fiction.

Fluids make up about 60% of your body’s total weight. To maintain the correct balance of substances in this internal environment, your kidneys will continuously filter about 180 litres of blood fluid (plasma) every day.

Thankfully, we don’t pee out 180L of urine, because our kidneys “throw back”........

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