The application for medical school *currently* automatically calculates two standardized GPAs. One is specifically for "Biology, Chemistry, Physics, and Mathematics' courses (the definitions are somewhere on the AAMC websites). The other is all other courses. Med schools can choose to care about either of those GPAs. Some schools have strict cut-offs for who they offer interviews to. Others do not. I think the most important thing for you is to take classes you find both interesting and (appropriately) challenging. If you burn out on classes that are too hard, you won't have any desire to keep on trucking through medical school. If you set yourself up for years of a major you don't like (even if it's easy), you will be hard pressed to care enough to slog through the long haul. Granted, I come from a liberal arts background where the goal of college was to "explore the world" rather than learn specific skills, so my bias is toward using those years to learn about yourself and the people around you (both in and out of class). All that knowledge will serve you just as well as your good scores or grades will when it comes time to apply to med school (if you end up deciding to stick with that).
