That is incorrect. In cases that are not defamation per se (per se cases are rare) you must explicitly prove damages. For example, if I say your sandwich shop sells dog meat but you cannot prove a drop in sales you can't file a slander/libel suit against me.

http://injury.findlaw.com/torts-and-personal-...asics.html

Elements of a Defamation Lawsuit

Defamation law changes as you cross state borders, but there are normally some accepted standards that make laws similar no matter where you are. If you think that you have been the victim of some defamatory statement, whether slander or libel, then you will need to file a lawsuit in order to recover. Generally speaking, in order to win your lawsuit, you must show that:

Someone made a statement;
that statement was published;
the statement caused you injury;
the statement was false; and
the statement did not fall into a privileged category.

To get a better grasp of what you will need to do to win your defamation lawsuit, let's look at each element more closely.