IPhone Question: Will syncing my iphone apps to my computer for the first time actually erase them and the information that they contain?

I’m looking through the apple boards right now but I can’t seem to find a definitive answer. I have never sunk my applications before on my iphone (for various reasons, first because I didn’t have a computer that I could sync the iphone to). When I go to sync my apps in itunes it warns me that the apps on my iphone will be erased. Is that really true? How do I get around this- as I’ve paid for a lot of apps on the phone itself and in a few apps, like my 4 track recorder, I have important info that I can’t lose. Any help appreciated.