This is me coming at it as a nontraditional-age person, because every 20 year old thinks they've found their calling for The Rest Of Their Life and that things are going to be Just Great after they get out of school. Then they either find out in their second year of school that they really want to join the circus. Or they get out of school and don't know what to do with themselves.
At that age you still have to ask yourself, who wants you to be a doctor? Yourself or your mom? You need to especially ask yourself this if you're going into some field that is really popular with parents: medicine, engineering, dentistry or law. Parents just somehow don't get as excited about us joining the circus, and really, speaking as a 31 year old, many 20 year olds (esp. if they're from the social group where their parents can afford to put 'em through med school) don't yet know the difference between what THEY want, and what MOM wants. I'd pay my own way through school if I had ten dollars for every ex-premed/ex-predental/ex-prelaw I've known, who was in the early-twenties age group.
The thing with the major... is it something you'd do/want to study if you DON'T end up becoming a doctor?
But let's say your passion is film. Sure, you can be a liberal arts major... but if you stop at a bachelor's (things like that happen), can you actually get a job? Do you have a backup plan in case you decide you can't stand body fluids?
And, it's easier to get a liberal arts or social sciences Master's or Ph.D. if your undergrad degree is science, than to do it in reverse: to backtrack and slog through four years of math and science that you didn't complete. I'm doing this, I had no idea I was going premed, and never took a single math class my entire college career. So yeah. Learn from the mistakes of people stupider than you.
Even if I ultimately end up in anthropology and not medicine, I'm in a better position launching from a biology degree than from an anthro degree.
Anthro = "do you want fries with that?"
Also - since changing my major to biology, I'm amazed how many scholarships are opening up. Sure, I could go to med school with my degree in art or anthro (two previous majors), too, but as a bio major, I have a better shot at actually paying for school. And yeah. At the school I'm transferring to (UC Davis), a general BA degree in Biological Sciences covers all the med prereq bases. But you also get to take nifty classes about plants (botany) and environment and stuff like that.