I did my research on a strictly Biology-related topic that is only indirectly related to Healthcare (Researching an organism that can act as a model for the signaling pathways of cilia in the human body) , and it felt like half of my interview at RVUCOM was focused around being able to talk through what I studied and what I learned. I was accepted, so for what it's worth, I feel like my research was helpful to my strength as an applicant.
That being said, research what is interesting to you, whether or not it is obviously medically-related. Biological studies on model organisms that relate to the human body are common in undergrad labs, and give just enough integration that they can be talked about in applications/interviews. Good luck!