And we thought it was the blood sucking leeches!
Demi Moore says the secret to her eternal youth is sex ...with her very youthful husband Ashton Kutcher.
"I would say that a lot of sex helps. It's the endorphins!" the 47-year-old tells the Sunday Mirror. "But there's more than that, it's also sharing a quality life with someone.
"I know I have someone who loves me for who I am and who I'm not. He loves me for my imperfections and that makes me feel so happy," she adds.
"I've aged, I don't look the same as I did in my 20s and 30s. But you've got to make the most of what you have."
It's true, she doesn't look the same as she did in her 20s and 30s – she looks better!
More (slightly stranger) youth elixirs in our gallery...