Ads often tout dietary supplements and vitamins as "natural" remedies. But studies show megadoses of some vitamins can actually boost the risk of heart disease and cancer, warns Dr. Paul Offit. iStockphoto.com hide caption itoggle caption iStockphoto.com Shots - Health News A Scientist Debunks The 'Magic' Of Vitamins And Supplements July 23, 2013 Physicians are partly to blame for the increasing popularity of untested treatments, says Dr. Paul Offit. Rather than pushing back against misguided patient demand, he says, doctors have "acted like waiters at a restaurant, simply asking, 'What would you like?' "