Pick a major that interests you. You will need to get good grades in college in order to apply for medical school. At the medical school I attended, the average GPA is reported to be 3.85, so even one or two B's can hurt your chances of acceptance.
Aside from this, any major is acceptable as long as you complete the prerequisite courses.
Typical medical school prerequisites include:
Biology: Lecture – 4 semesters; Lab – 1 semester
General Chemistry: Lecture – 2 semesters; Lab – 1 semester
Organic Chemistry: Lecture – 2 semesters; Lab – 1 semester
Biochemistry: Lecture – 1 semester
General Physics: Lecture – 2 semesters; Lab – 1 semester
Math: Statistics – 1 semester
English: Rhetoric (Composition) and Literature – 2 semesters
I chose biochemistry because it overlapped well with premed requirements and I was able to graduate college in 3 years.
Years ago was told not to be a classic premed student. Take required science courses, usually biology, physics, chemistry, organic chemistry. Then focus on liberal arts courses, you will receive enough science in med school. Get an education in undergraduate school. Found that was excellent advice. Research what science courses are required by medical schools you are interested in attending. Also get involved in extracurricular activities.