Populate fields using user attributes

I know how to link a database record to user (using user name) and for the user to be able to edit the record. What I would like is if the user updates their user email, an email field within the database is automatically updated.

I have users complaining that they update their user email but their entry in the database remains unchanged. I explain why this is, but they would like for their user email to be the master.

Any suggestions would be appreciated.