The Truth About Washing Your Salad Greens

Photographed by Ruby Yeh.
Update: This post has been updated to include quotes from Judy A. Harrison, PhD, a food safety expert at the University of Georgia.

This article was originally published on July 20, 2016.

Two people in the U.K. died this week due to serious E. coli infections linked to packaged salad mixes. To prevent more infections, Public Health England is advising consumers to wash their salad mixes. This, plus the recent outbreak of listeria traced back to packaged salads in the U.S., has us a little bit on edge about dealing with greens. So, should we always be washing our greens — including those pre-packaged salads? As it turns out, it's not easy to get a straight answer.

There's no question that you should thoroughly rinse fresh greens, taking care to remove any remaining soil. But packaged salads that are "ready to eat," "pre-washed," or even "triple-washed" typically go through a fairly intense process. "Pre-washed greens are treated with a mix of water and a food-grade sanitizing agent, like hydrogen peroxide or chlorine,” Randy Worobo, PhD, told Real Simple.

So, according to one line of reasoning, washing those greens at home is pointless: Anything that's already made it through triple-washing is also undoubtedly going to survive your mild kitchen-rinsing.

"[Consumers] are more likely to contaminate the product in their kitchen than they are to remove any harmful microorganisms that had not already been removed by washing during processing," Dr. Harrison tells R29 via email. Indeed, many experts believe another rinse is unnecessary at best and may actually introduce new bacteria at worst.

On the other hand, after the massive spinach-linked E. coli outbreak of 2006, greens are fighting against a bad reputation. And it's not entirely undeserved: A Consumer Reports investigation found higher-than-recommended levels of several types of bacteria hiding in packaged greens, although they did not find the dreaded E. coli O157 strain responsible for the U.K. deaths. Also, even if your lettuce is clean, it's easy to accidentally contaminate it if you're whipping up a salad while simultaneously cooking with raw meat.

The truth is that, "once pathogens get on or inside produce, they are difficult — if not impossible — to eliminate," says Dr. Harrison. So keeping your lettuce safe actually starts way before it gets to your sink. The quality of the soil it's grown in, the water used for irrigation, and the hygiene practices of produce workers all play a role in stopping contamination before it starts.

"Salad greens, as with any fruit or vegetable, are raw agricultural products that must be grown, processed, packaged, and transported using best practices to keep them safe," says Dr. Harrison. "[But,] no matter how good a system is, occasionally there can be mishaps."

Although it may seem like we're seeing lettuce-related outbreaks more often, Dr. Harrison says that they're still relatively rare compared to the staggering amount of greens we eat. But we're more aware of them than ever before, making them seem more common than they really are. But overall, we're actually getting better at dealing with foodborne illness issues thanks to DNA fingerprinting techniques that help trace the source of an outbreak, she adds.

Still, the bottom line is that, whether you wash them again or not, packaged salad greens always come with some risk — and the only surefire way to know your greens are free of those bacteria is to cook 'em. "[So,] if you want absolute safety for lettuce, you'd have to stir-fry it," Robert Buchanan, PhD, at the University of Maryland told NPR. But if that's not part of your plan, be sure to store the greens in the fridge (at or below 40 degrees Fahrenheit), take care when preparing other foods — like meat — that may contaminate your salad, and accept the tiny risk that inherently comes with eating those nutritious leaves.