Any laws about writing ebooks about alternative medicine?

I've recently started writing an ebook about a herbal medicine that (in mine and others' experience) has cured many ailments. I've looked around to see if there would be any legal issues for me when writing about this, but I can't find much info about how this works in the Uk. I have been advised that in the States, you absolutely cannot claim to cure anything when you write your sales copy, but it's fine to do so in the book itself, according to the First Amendment. I'd like to know what the rules are over here - not that I am going to claim to cure anything, but it's best to know all the rules to avoid any trouble!