Is that salad safe to eat? How to guard against germs in leafy greens. (2024)

The good news: You don’t need to give up lettuce — leafy greens are highly nutritious. You just need to take a few precautions. Consumer Reports experts answer questions about the risks of bacteria in lettuce and how to minimize them.

Q: How does lettuce get contaminated?

A: There are a few ways. Irrigation water, which is necessary to grow crops in areas that don’t get a lot of rain, creates a pathway for contamination, especially if the lettuce field is near livestock farms. Cattle can carry deadly strains of E. coli, and their manure, which contains the bacteria, can seep into irrigation water and contaminate crops. Even when leafy greens are grown free of harmful bacteria, contamination can still occur during harvesting, processing or packaging. And because packaged salad greens are processed at a small number of facilities across the United States, bacteria such as listeria can easily spread from one batch to many.

Q: Does washing lettuce remove bacteria?

A: Not entirely. When bacteria such as E. coli come into contact with lettuce, they’re almost impossible to wash off completely. That’s often because bacteria can get inside the leaves of the greens as they’re growing, when contaminated water taken up by the roots is dispersed throughout the plant. What’s more, surface bacteria can adhere stubbornly to wrinkles and grooves in leaves. So whether the packaging says “triple-washed” or you wash it yourself, bacteria could still be present — and even a small amount can make you sick.

Q: What about soaking greens in vinegar?

A: It won’t eliminate bacteria, but some experts say that soaking your greens in white vinegar (or a vinegar-and-water solution) for about 10 minutes, then rinsing them with water, may help reduce bacteria levels. Your greens may retain a slightly vinegary taste, but most salad dressings contain vinegar anyway.

Q: Are some types of lettuce safer than others?

A: Because contamination can happen anywhere from farm to table, no single type of leafy green is risk-free. But hydroponic lettuces (which are greenhouse-grown) are less likely to be contaminated by bacteria from animal droppings. Their cleanliness depends on the source of the water used to grow them and whether proper safety practices are followed by the people who handle the greens, says James E. Rogers, Consumer Reports’ director of food safety research and testing.

Whole heads of lettuce (instead of bagged greens) may also be safer. While whole heads don’t necessarily have lower bacteria levels than packaged greens, their inner leaves are less exposed to sources of contamination and are handled less than bagged greens. This reduces the opportunities for contamination.

Q: What else can you do to make your lettuce safer?

A: Bacteria multiply at room temperature, so it’s crucial to refrigerate bagged lettuce promptly. “As you would with meat and poultry, don’t let bagged lettuce stay out of the fridge for too long,” Rogers says.

In addition, the longer that lettuce sits in bags or containers, the more opportunity bacteria have to grow, so buy packages with expiration dates as far in the future as possible, and don’t buy more than you can eat in a few days. If even a few leaves look damaged, slimy or bruised, don’t eat any of the greens in that package.

Another strategy: Opt for leafy greens that can be cooked, like spinach or kale. The heat will kill bacteria. This is particularly important for people who are more susceptible to the ill effects of food poisoning, such as those who are immunocompromised, pregnant or elderly.

Consumer Reports is an independent, nonprofit organization that works side by side with consumers to create a fairer, safer, and healthier world. CR does not endorse products or services, and does not accept advertising. Read more at ConsumerReports.org.