Every particle in your body doesn’t get swapped out which is how they can do molecular analysis on things like teeth and bones to try and pin point where you gr

Every particle in your body doesn’t get swapped out which is how they can do molecular analysis on things like teeth and bones to try and pin point where you grew up. Even if every cell in your body is replaced over a 7 years period which they don’t since not all cells actually undergo mitosis or are even replaced through stem cells not every molecule in your body needs to be replaced for that to happen and in fact it doesn’t it would be exceedingly wasteful and impractical. So the many if not most hydrogen molecules you were born with are still probably somewhere in your body.