At some point every drop of water we have ever consumed passed through some creature’s kidneys. Drink up.
The scientists say that every breath we take contains molecules that also passed through the lungs of George Washington.
Not sure if that's "settled science" like Algore and his global warming, but there you have it for what it's worth.
I remember a magazine ad for Culligan water softeners:
“The water you drink may have quenched the thirst of Julius Caesar!” as it depicts the noble Roman quaffing his goblet.
(One of those things that makes you say hmmm.....)