Did he have guests who claimed to be Immortal?

I'm having a brain fart as of late after discussing immortality with my friend and I distinctly remember a talk show from the early 90s that featured guests who claimed to be immortal. They were, at that time, in their late 30s, but had claimed to have attained the secret to eternal longevity and that they would never look older or physically age from that point on.

I can't remember if this was on Donahue or another show like Sally Jessie Raphael.

Can anyone corroborate this with me?