What is the subject in this sentence: It is not surprising that food is such an important part of different cultures around the world

Question

It is not surprising that food is such an important part of different cultures around the world.

I don't know if the subject is it or food. And I need an explanation about this case

Answer 1

it is a proxy for the clause that food is ... world.

Compare:

[That winter is cold in Alaska] is a well-known fact.

[It] is a well-known fact [that winter is cold in Alaska].

Extraposition is the overarching grammatical term for this sort of movement, here of a clausal subject to the end of the sentence with "it" being substituted for the clause and placed in subject position. There, "it" is sometimes called "dummy it" or "expletive it".

Answer 2

The subject in your example is "it". This as all about one of the information packaging constructions called subject extraposition. Compare:

[1] [That food is such an important part of different cultures around the world] is not surprising.

[2] It is not surprising [that food is such an important part of different cultures around the world].

In the basic version, [1], the subject position is filled by a subordinate declarative content clause, bracketed.

In the version with extraposition, [2], the subject position is filled by the dummy pronoun "it" and the subordinate clause appears at the end of the matrix clause in extraposed subject position.

The version with extraposition is the default one, as far as information packaging is concerned.

One reason is that it is much more common; this is because subordinate clauses tend to be heavier (longer an structurally more complex) than noun phrases, and there is in general a preference for placing heavy material at the end of the matrix clause where it's easier to process.