If every cell in your body is replaced roughly in 7 years, why do the affects of smoking and other bad habits still affect people who quit?

Question

If every cell in your body is replaced roughly in 7 years, why do the affects of smoking and other bad habits still affect people who quit?

In: Biology

Answer 1

All your new cells are created by existing cells. Cells that are very healthy can create a lot of very healthy cells to replace dying cells. Cells that are damaged by poison don’t work as well, so they can’t make very good replacement cells. This damage stacks up over many generations of cells, where each generation can’t work as well and also can’t make good new cells to replace them.