Every year, supplements send roughly 20,000 people to the emergency room.
Last year, the world's largest dietary supplement maker, GNC Holdings Inc, agreed to pay $2.25 million to avoid federal prosecution over its alleged sale of illegal pills and powders.
And the Food and Drug Administration has ordered the makers of several supplements to recall their products after scientists found traces of illegal and potentially dangerous molecules in their formulas.
Still, while many supplements are useless, there are others that we can't enough of simply by eating a healthy diet.
So here are the supplements you should take — and the ones to avoid: