Can you get the PhD in anything?

I know that the MD/PhD programs out there are usually for like academic medicine/teaching, and that the two sort of go hand in hand. But can you do like an MD/PhD with the PhD like on global health/development/something policy or similar in nature still in that 7 year track? Or the PhD usually reserved for still more of the hardcore science.
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums