Sara Martín reads bedtime stories with her children. When the kids were younger, she says, staying up to date on their frequent immunizations was tough, because of cost and transportation issues. Lauren M. Whaley/CHCF Center for Health Reporting hide caption

itoggle caption Lauren M. Whaley/CHCF Center for Health Reporting

California is one of 20 states that allow parents to opt out of vaccination requirements for reasons of "personal belief." About 10 percent of students in the Santa Monica-Malibu school district are not immunized. Justin Sullivan/Getty Images hide caption

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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

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