Filing Nails: with or without polish? What is best practice?

Are you a nail polish wearer who files your nails down, or even to shape them while wearing varnish?  I know some think this is a good habit, but truth be told it is harmful for your nails.

Your nails are made up of layers upon layers of straw-like columns or fibres running from your cuticle to the end of the nail.  The hard nail we can see is of course dead tissue, which cannot repair itself.  For this reason we have to be very careful not to weaken or damage these top layers in any way.

In fact, nail polish does glue these straw-like columns together in order to prevent splitting.  However, it only "protects" them slightly and on the very outside layer.  What about all the underlying layers that help to provide your nails with strength, flexibility and a healthy appearance?  They will become weak and damaged.

Recently I tried a crystal nail file by Essie.  My curiosity got the better of me since so many bloggers say they swear by their crystal files.  Of course, I file daily with the Contour Nail file by ASK Cosmetics to seal the ends of my nails.  If they aren't sealed almost every day, snags can occur or I might catch them on things.  Although the crystal file feels only slightly "gritty" it still leaves those white shavings that everyone has experienced before while filing.  Those shavings are evidence that you are grabbing, ripping and tearing the nail fibres, thus weakening them.  This can lead to several issues such as:  cracking, splitting, breaking, etc.

This is also the reason why you are advised to only file in one direction with conventional files or emery boards.  The damage would be much greater if you filed (by grabbing and tearing the fibres) in both directions. 

What kind of file are you using?  Have you ever thought about the little white shavings? 

I am interested to know your thoughts.  Lisa M.