Why You Should Always Wash Your 'Pre-Washed' Lettuce

If you encountered someone who didn't wash produce that they'd purchased at the supermarket before eating it, you'd probably ask them if they had a death wish; supermarket produce is notoriously dirty. One sampling by Reuse This Bag found that traditional grocery store produce hosted 746 times more bacteria than a car steering wheel! But what about the bagged lettuce, which usually boasts of being "triple washed"? Isn't that OK to just eat straight out of the bag? Well, maybe not.

"Most of the information suggests that pre-washed or triple-washed produce should be ready to eat directly from the bag," James E. Rogers, director of food safety research and testing at Consumer Reports, told us when reached for comment. "However... there is the potential of the produce being contaminated with pathogenic bacteria that are not removed by any type of washing because they are in the 'nooks and crannies' of the plant and cannot be removed by washing (only by cooking it)."

When your bagged lettuce is washed in the production facility, it's typically submerged in a solution that contains a little bit of bleach, which is supposed to kill off all the bacteria. But a study by UC Riverside found that up to 90 percent of the bacteria on bagged spinach remains there during this washing process, because the texture of spinach, with its peaks and valleys, makes for a perfect bacterial breeding ground.

After it's rinsed with the bleach solution, the surviving bacteria can grow and infect other leaves as well; that's part of the reason why bagged greens feature in some of the biggest food recalls.

While the study focused specifically on baby spinach, it calls into question the safety of any pre-washed salad greens. In short, that "triple washing" doesn't actually accomplish too much, and even if it does, the remaining bacteria may have time to grow and spread between the wash stage and your plate. So before eating bagged spinach, dump it out into a large, water-filled bowl and stir it around with your hand before drying it thoroughly in a salad spinner. This is one of the easiest ways to avoid getting food poisoning.