While I was an undergrad, I wrote a paper on topic A with my advisor. Currently, I'm working in a research institution with an Economist whose work mainly lies on topic B. However, I've come to understand that I do not like A or B, but I'm more interested in topic C, and I've done some independent study on topic C. I'm thinking of asking my undergrad advisor and my current Economist for recommendation letter to apply for PhD in topic C.
How will admission committee for PhD view such recommendation letters from academics whose work is not on my current interest? That is, will it have any negative influence in my application, if I seemed to change my interest often?
To be specific, all topic A, B and C is under the field of Economics, but are vastly different from one another (especially the switch from A to B; it was like learning completely new subject). Knowledge gained from A and B can only be partially transferred to C.
Related, but does not quite answer the question that I have: Value of recommendation letters from professors in a different field. My question is more focused on the fact that two recommendation letters will show my interest in certain research topics were very short-lived.