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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Some sports supplements contain the ingredient DMAA. The FDA has warned that DMAA may not be safe. iStockphoto.com hide caption

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Popular Workout Booster Draws Safety Scrutiny
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Despite public health campaigns urging women in the U.S. to take folic acid, many are still not taking the supplements when they become pregnant. iStockphoto.com hide caption

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Folic Acid For Pregnant Mothers Cuts Kids' Autism Risk
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There might be much more caffeine than you think in those supplements you're taking. There also might be much less. Janine Lamontagne/iStockphoto hide caption

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Federal health officials recommend 1,000 milligrams of calcium per day for people younger than 50, but some are overdoing it. iStockphoto.com hide caption

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Too Much Calcium Could Cause Kidney, Heart Problems, Researchers Say
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Staying fit and eating well can help cancer survivors, too, a review of the latest evidence shows. Lucy Pemoni/AP hide caption

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