How much saliva do we produce in a lifetime?

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!

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Luis Villazon

Q&A expert

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.