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Corn

Worst

Fiber-rich corn is good for you, but it also contains cellulose, a type of fiber that humans can't break down easily because we lack a necessary enzyme.

Our evolutionary ancestors were probably able to break it down with bigger, stronger teeth, Anderson says. If you chew corn longer, you can probably digest it just fine, she says. But wolf it down and it may pass through you undigested, and cause gas and abdominal pain.

Next: Yogurt