An apple a day keeps the doctor away, they say. And while people stand by that conventional wisdom, researchers would wish patients would perhaps not. Doctors included. According to Dr. Vinay Prasad of Oregon Health and Science University, nearly 400 routine practices have been overturned by new studies. Fish oil will apparently not protect you against heart disease, nor will Ginkgo biloba or testosterone keep your memory sharp. Forget the step counters and calorie trackers. They may be holding you back from losing even more weight. And exposure to peanuts won’t bring on peanut allergies in young children either. What conventional medical wisdom do you stand by?