You might want to clean your bathtub after you read this.
Asked by: Iqra Shahzad, London
Your saliva is mostly recycled, rather than produced, because you are constantly swallowing and reabsorbing it. But the flow rate is around 30ml of saliva an hour – a bit more when you’re eating, a bit less when you’re sleeping. That’s a wine bottle full every day, or 20,000 litres in your lifetime. In other words, 53 bathtubs full to the brim with saliva!
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.
Subscribe to BBC Science Focus Magazine and try 3 issues for just $9.95
Discover our latest special editions covering a range of fascinating topics from the latest scientific discoveries to the big ideas explained.
Listen to some of the brightest names in science and technology talk about the ideas and breakthroughs shaping our world.
By entering your details, you are agreeing to our terms and conditions and privacy policy. You can unsubscribe at any time.