Maybe you’ve seen a non-GMO label on a cereal box, or a friend told you she only buys GMO-free foods at the grocery store. Or maybe you read something on the Internet about the supposed “dangers” of GMOs.

Should you really be worried about GMOs in your food? And what exactly is a GMO, anyway?

Ruth MacDonald, professor and chair of the food science and human nutrition department at Iowa State University, says she...