Close to half of American adults take vitamins every day. Yet decades' worth of research hasn't found any justification for our pill-popping habit.

That isn't to say we don't need small amounts of vitamins to survive — without vitamins like A, C, and E, for example, we have a hard time turning food into energy and can develop conditions like rickets or scurvy. Here's the thing: Research shows we get more than enough of these substances from what we eat, so no need for a pill!