Sentence Correction

Doctors generally agree that such factors as cigarette smoking， eating rich foods high in fats， and alcohol consumption not only do damage by themselves but also aggravate genetic predispositions toward certain diseases.

　　（A） not only do damage by themselves but also aggravate

　　（B） do damage by themselves but also are aggravating to

　　（C） are damaging by themselves but also are aggravating

　　（D） not only do damage by themselves， they are also aggravating to

　　（E） are doing damage by themselves， and they are also aggravating

OA : A

I was able to arrive at the correct answer. My question is about the non-underlined portion.

Are these things parallel?
cigarette smoking, eating foods, alcohol consumption ? I believe that "eating" foods is not. Correct?

Thanks