Can I just update my jailbroken iPhone?

I don't want my phone jailbroken anymore? I want the newest version of iPhone software I don't want the jailbreak, can I just update my iPhone from the device or do I have to restore it first.

I would suggest you make a backup, just in case something happens. Make a backup in iCloud, or if you've got iCloud enabled, just check when the latest update was created, and if its good enough (message history, safari bookmarks, notes, etc… ) for you, proceed to update, it should be fine. You don't need to restore first and then update. After the update if you're missing anything, just restore form the backup from icloud, and to restore any apps that have gone missing, just open up the app store and select the updates tab from the bottom. In the updates page hit the purchased button and you'll see all of your previously purchased apps.

You will not have an issue when updating straight off without restoring first. Enjoy iOS 6 ;)

Restore it with itunes.