Tag question

Hi everybody.
Which would be the right choice and why:
It is very important that we eat healthy food, isn’t it/don’t we?
Some people say that isn’t it would be the right choice, but nobody told why? And why not don’t we?
Thanks in advance

Because the main clause begins with “it is…”.
When you form a tag question, the tag should point to the main clause.
“we eat…” is a subordinate clause.

Thank you. That was really helpful.

Though the answer is ‘isn’t it?’, the explanation is not correct. Take this example:

I think he is very smart, isn’t he? > Here the main clause is ‘I think’ and the tag is not ‘don’t I?’

So, the tag applies to what is being predominantly talked about.