Safe? Yes. I’ve done it on many sites, and I’ve ony had an issue with one but that was caused by some out-dated plugins that weren’t supported any logner (third party stuff that the client wanted… terrible choice by them).
As for losing anything, there’s no reason why that should happen as the update doesn’t affect anything to do with your content.
Having said all that, please be sure that you do have a current backup of all of the sites files plus the database. That way if anything does go astray you’ll be able ot revert back to a known working version and trouble-shoot from that point.
