PHP-Security - How to Prevent Spam Submissions

I have a cakephp recipe website. I've been getting spam recipe submissions from a non-registered user. How is it possible to submit a recipe when not registered or logged in and how can I prevent it?

Requiring them to register won't cut down on the spam a whole lot so whether you enforce that is your decision.
The best anti-spam tool so far is a CAPTCHA. reCAPTCHA is pretty much the de-facto standard but there are a couple other popular ones out there too.

I found the problem. I wasn't using the auth component for my recipes controller, I was only using it for my users controller. It's been fixed now.