Dietary supplements aren't closely checked by regulators, and because no one independently tests them, you can't always be sure what's in the bottle—some might even have harmful stuff.

Unlike pills you need a doctor’s prescription for, vitamins and supplements you buy over the counter aren’t tightly checked, so what’s in them can vary a lot — sometimes they have too little of the good stuff, or even bad stuff mixed in.

When supplement companies make confusing or false claims, people don't understand the risks, and companies aren't clear about what's in their products, it leads to people using supplements without knowing the facts — and that can hurt public health efforts.

Mixing the science behind supplements and healthy foods could make store-bought health products more trustworthy, better regulated, and more helpful for people's health.