This is not actually true. It is unlikely any of the molecules
in the human
body were part of a star, as they have all changed their forms in chemical reactions during the past four or five billion years since the earth was formed.
If you mean all of the atoms in ones body were once in a star, this is closer to the truth, but still not certain. There are a lot of hydrogen atoms combined with other heavier particles in our bodies, and hydrogen was formed shortly after the big bang, so never had to have been in a star.
So when trying to impress your love interest with the wonder of the universe, make sure you say:
"All of the heavier elements in our bodies were once part of a star, except possibly some which may have been formed in the earth due to radio-active decay of larger atoms, which themselves must have been part of a star in order to be formed"
but you don't have to if you don't want to