Is there a way to avoid losing mail message downloaded list when doing iOS updates?

Every time I update my iPhone 5 to the latest iOS, I find that I have to re-download all the old email that I had previously downloaded, the first time that I start the mail app after I do the update.

I suppose the mail app is not saving the status of each message when it is synced with iTunes.

Has anyone found a way to keep the status updated on the itunes backup?