# Why do bodies age if their cells are constantly replaced?

**URL:** <https://boards.straightdope.com/t/why-do-bodies-age-if-their-cells-are-constantly-replaced/8351>\
**Category:** Factual Questions\
**Created:** [March 9, 2000, 8:20pm UTC](https://boards.straightdope.com/t/why-do-bodies-age-if-their-cells-are-constantly-replaced/8351 "2000-03-09T20:20:00Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Sean\_Crotty](https://avatars.discourse-cdn.com/v4/letter/s/dbc845/32.png) [@Sean\_Crotty](https://boards.straightdope.com/u/Sean_Crotty)\
**Post date:** [March 9, 2000, 8:20pm UTC](https://boards.straightdope.com/t/why-do-bodies-age-if-their-cells-are-constantly-replaced/8351/1 "2000-03-09T20:20:00Z")

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Dear Cecil, Straight Dope Science Advisory Board, or Teeming Millionth:

I’ve heard that every cell in my body eventually dies and is replaced by another cell. This “serve, die, and get replaced” cycle will continue until, eep, my death. Supposedly I could say that my entire body is comprised of 100% different material after “x” months. (“x” being a number that I don’t remember - but could be, for argument’s sake, eleven) If that’s true, then why do: my joints stiffen, my scars stay forever, and other yucky aging things happen as I get older? It seems to me that all these vibrant, springy new cells have no right making me saggy and sluggish.

Thanks!