Does Game Center email friend requests to people who don't have it?

I don't want to spam my friends with requests for them to join Game Center if they haven't already. Does the friend request feature do that? Or do the friend requests only get sent to the emails I list that are already associated with Game Center accounts? I want to send Game Center requests to all the friends of mine who, according to Facebook, use the Facebook for iPhone app (80 people). Before I do that, I'd like to know what happens.

I'm guessing that some of those friends don't play *any* video games of any kind, let alone use Game Center. I don't want their email inboxes spammed on my behalf.