Your healthy choice is actually one of the riskier options on the menu at chain restaurants.
"I'd eat sushi before I ate a salad," Marler said. "I wouldn't eat it at a 7-11, but I've eaten sushi at a good sushi restaurant."
While cooking veggies and meat can kill germs, salads bring together a lot of raw foods that have had countless opportunities for contamination. Restaurants that buy pre-chopped lettuce from suppliers put themselves at even greater risk.
"Not every lettuce leaf in the field is contaminated E. coli, but some of them are," Marler said of the risks of pre-washed, bagged lettuce. "And when you mix and match it at a processing facility and chop it up, you get what you get."