Directly from my pre-med advisor:
<http://www.aas.duke.edu/trinity/prehealth/faq/>
2. Surely med schools will be impressed with me if I double-major? triple-major?
No.
<http://www.aas.duke.edu/trinity/prehealth/prepare/scheduling.html>
Choosing a Major/Double Major/Minor. It is possible to major in any academic discipline and still complete the science courses required for health professions schools. Health Professions schools do not prefer one major over another major. Thus you should major in whatever area you find exciting and appealing. Health professions schools do value original scholarship in your field of choice. Consider doing an independent study in your major and writing a thesis during your senior year. While health professions schools value a curriculum that results in broadly educated applicants, they will evaluate your curriculum by looking at the courses that you take, rather than by simply looking for particular credentials such as second majors or minors. Completing two majors or a minor will not make you more competitive for a health professions program.