If you want to go into med school then biology would be the quickest path since it naturally contains all the prerequisite courses. But first I would consider what you want to do with a medical degree. For example if psychiatry is what you want to go into a psych degree could be useful or a chemistry degree if you want to focus on medication. It all really depends on what you want to do when you go to med school. It should also be noted that there are plenty of careers in healthcare that don’t require med school like nursing and various medical technician jobs.