Hi - If I write "the meal itself should contain" in a sentence, is this correct? I was told that "it self" should only be used to a person or an animal.

I think your sentence is acceptable. The sentence is also fine without the word 'itself', so why the it is used would depend on the context - which can only be guessed at. By the way, I wouldn't ever use 'itself' in reference to a person.

Yeah, Tomster's right. There's no need for the itself, but it is acceptable.

More on emphatic and reflexive pronouns here.