I've tried Slackware, Debian, Ubuntu, Suse and Fedora as host, and gave up on all of them. Too many things had to be changed to the host, some changes (partially) messed up the hosts. Not the way to go. This: vii. Host System Requirements
needs to be your starting point.
Many have tried with their own host and failed, search the Linux From Scratch forum for Ubuntu to get an idea of the troubles you could face.
The LFS liveCD was specifically made to be a good host for the LFS build. The only other host that can be used is LFS itself (but there is always that first time....).
Hope this helps.