Ask someone who investigates foodborne illness for a living what they won't put on their plate, and the list is shorter—and stranger—than you'd expect. It's not that these experts live in fear. Most will tell you that all food carries some risk, and the real skill is deciding which risks are worth taking. Frank Yiannas, the U.S. Food and Drug Administration’s former deputy commissioner for food policy and response, says he doesn't think of foods as simply "good" or "bad." Instead, "I approach everything with what I would say is a quantitative risk assessment," he says. "I'm calculated." Still, after...