Question: Hi Dave, I am a student from Carshalton Boys Sports College, I would like to know: How many cells will die off in a year in the average 11 year olds body? Thank you very much

David Christensen answered on 21 Nov 2013:

That’s a tough question and I’ve just tried to google it and got some very different answers!

At the moment, we don’t have a very good guess at how many cells there are in the body, but think it is roughly 40 trillion in an adult, so maybe 30 trillion in an 11 year old (that’s a complete guess!).

Apparently about 25 billion cells die every day in average 8-14 year olds! This means that about 9, 125, 000, 000, 000 cells die each year on average! In other words that is 9.125 trillion! So, it seems that about a third of your body is replaced every year! That isn’t exactly true because some cells die a lot faster than others. For example, apparently we make 2.4 million new red blood cells every second. This is much faster than the rate at which we have to make new cells in many other parts of the body.

Thanks for the question rishipatelnash! I’ve had fun looking things up to try to answer it. Those numbers are crazily big!