Why Greens Keep Making People Sick

Story at-a-glance -

  • Due to a large breakout of E. coli, the CDC has advised American consumers to avoid eating romaine lettuce that was grown in Yuma, Arizona
  • Because it can often be difficult to trace the origin of salad greens, I advise you to avoid eating any romaine or bagged lettuce mixes until the contamination issue is resolved
  • The love affair Americans have with prepackaged, prewashed greens is further indication of the tremendous disconnect that exists for many consumers, their food and the soil in which it is grown
  • You can limit your exposure to E. coli and other harmful bacteria by cooking your greens, growing your own or purchasing them from a local farmers market

By Dr. Mercola

The news across the U.S. with respect to contamination involving bagged and chopped romaine lettuce continues to worsen. After a multistate outbreak dating back to March 13, 2018, involving at least 121 known Escherichia coli (E. coli) infections spanning 25 states, including one death, the U.S. Centers for Disease Control and Prevention (CDC) has isolated the problem lettuce to Yuma, Arizona.1

Because it takes an average of two to three weeks for this type of outbreak-related illness to be reported, even more cases are expected to be made known in the coming weeks.

To date, more than 50 people have been hospitalized with a nasty E. coli infection and at least 14 victims have developed hemolytic uremic syndrome, a type of kidney failure, making this quite a serious matter.2 Yuma-grown greens purchased at the grocery store, as well as those served in restaurants, are equally suspect. Sadly, most bagged salad brands do not identify the region where they are grown and processed, making identification difficult.

For that reason, until further notice, consumers are advised to avoid consuming all types of romaine lettuce, including hearts and whole heads, in addition to bagged and chopped romaine, as well as any salad mixes containing romaine grown in the Yuma region.3 Rather than guess if your favorite salad greens are safe, the wisest move is to avoid buying or eating any romaine lettuce or mixes containing romaine until the situation improves.

If you have any doubt, throw it out! Thankfully, there are many other salad greens and vegetables you can eat safely until this situation resolves. I'd also like to suggest a few tips that will help you enjoy salad greens and other produce safely going forward.

Why Are There so Many Health and Safety Issues With Salad Greens?

It's no secret U.S. consumers love the convenience of prewashed produce that is sold in bags, clamshells and tubs. Unfortunately, those types of greens are precisely the ones continually implicated in outbreaks associated with foodborne illness. In fact, says The Washington Post, food-safety experts suggest "convenience greens — those handy bags of prechopped and prewashed salads — carry an extra risk because they come in contact with more people and machinery before they arrive on your plate."4

E. coli is quite common — its many strains are found in food and the environment and also live in animal and human intestines. Thankfully, most E. coli infections are tolerable, if not harmless. The types of E. coli known to cause illness are often transmitted through contaminated food and water or through contact with animals or people. For example, in a large 2006 outbreak of E. coli involving spinach, wild pigs and well water were suspected causes.5

The particular strain currently in question with respect to romaine lettuce, however, is not your average E. coli. It is Shiga toxin-producing E. coli (STEC) O157:H7, which is known to be particularly dangerous.

In the U.S., the CDC says an estimated 265,000 people suffer from STEC infections annually; the O157:H7 variety is responsible for more than one-third of those illnesses.6 While people of all ages are susceptible, the elderly and young children are most likely to be severely affected by STEC's unpleasant side effects.

Generally, symptoms appear one to 10 days after eating the contaminated food item and may include bloody diarrhea, stomach cramps and vomiting. The age range for the current outbreak, notes the CDC, is from 1 to 88 years, with a median age of 29, again suggesting all populations are vulnerable to this strain of E. coli.7 To date, no one brand, grower or supplier has been tagged as the source of the contaminated lettuce.

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Do You Know Where Your Salad Greens Are Grown?

Due to the industrialization of our food system, Americans eat produce from all over the world, regardless of whether it is in season locally. It's not unusual to go to the supermarket and return with fruits and vegetables grown and harvested in Canada and Mexico, as well as countries in Europe and South America, among others. Although enjoying seasonal produce raised far from home has become the norm, this convenience is not without a cost.

According to The New York Times,8 the majority of bagged romaine lettuce provided to grocery stores and restaurants across North America is grown in California's Salinas Valley. There is, however, one exception: In late fall and winter, the industry makes a seasonal move to Yuma.

Given the timing of the current E. coli outbreak, authorities believe the infected romaine was very likely grown in Yuma. While more details will be forthcoming, it seems likely the outbreak was caused either by an animal defecating in a field or some form of contaminated water runoff.

It's worth noting that concentrated animal feeding operations (CAFOs) are a major source of water contamination throughout the U.S. Even the Arizona Department of Environmental Quality (ADEQ) states, "Nationwide and in Arizona, the potential for surface and ground water pollution exists through livestock facility discharge of manure-contaminated run off to natural waterways and through wastewater leaching to aquifers."9

While the source of the outbreak has not yet been pinned down, it's certainly possible that industrialized agriculture has played a role. On a brighter note, because most of the industry's bagged romaine production shifted back to California in April, says The New York Times, the Yuma-grown produce should be out of the food supply shortly.10

"Hopefully with it being in one particular growing region and that region moving to California, it won't be too much longer [before you can begin eating romaine again]," said Laura Gieraltowski, Ph.D., who leads the foodborne outbreak response team within the CDC's outbreak response and prevention branch. "It's a fast-moving outbreak," she said. "We're getting reports of new illnesses daily from our state and local health departments."11

Seven Reasons Why You Should Avoid Packaged Greens

Given the health concerns about prepackaged romaine and other processed greens, it may be time to make a change. Below are seven reasons you may want to avoid packaged greens:12


Chemicals such as chlorine are routinely used during the rinsing process for precut, prepackaged greens as a means of trying to kill off bacteria such as E. coli and salmonella.13

The use of chemical washes, though not safe for anyone, are of particular concern if you are sensitive to chemicals. Researchers at the University of California, Riverside (UCR) found bleach rinses to be somewhat ineffective for cleaning baby spinach, noting while it caused bacteria to detach from the greens, it did not always kill the bacteria, meaning it could still make its way into your kitchen.14,15 


A continued reliance on prepackaged, convenience greens only further disconnects you from the reality of where your food comes from, the needs of the soil it is grown in and the hard work it takes to grow these crops. While some may view processed greens as a cut above other types of processed food, they are still less than ideal because nature did not intend for us to eat the majority of our food out of shiny packages we purchased from the grocery store.

Frogs and feces

In 2017, a California woman discovered a small frog in a prepackaged spring mix she had purchased from Target — as she was eating it, begging the question, "Do you know what is in your bagged salad?"

After recovering from an episode of vomiting and the shock of nearly ingesting the dime-sized creature, the woman opted to keep it as a family pet.16 Tests performed by Consumer Reports in 2015 on 208 prewashed salad mixes, representing 16 brands, found bacteria suggesting poor sanitation and fecal contamination, in some cases at high levels. They stated:17

"Several industry experts we consulted suggested that for leafy greens, an unacceptable level of total coliforms or enterococcus is 10,000 or more colony forming units per gram (CFU/g) or a comparable estimate.

In our tests, 39 percent of samples exceeded that level for total coliforms and 23 percent for enterococcus. Results varied widely among samples, even within the same brand, from undetectable levels of those bacteria to more than 1 million CFU/g."

Nutrient loss

Most people choose bagged lettuce and other greens for the convenience. The fact they are prewashed and precut perhaps draws some to eat greens who otherwise would not. While washing is meant to clean produce, says CNN Health, it "can also damage plant tissues and expose them to oxygen dissolved in the washing water.

This can cause a loss of vitamins that are water-soluble and sensitive to oxygen, such as vitamin C and the B vitamin folate."18 For this reason, uncut produce is usually a better choice.

Packaging waste

No matter what type of greens you select, when buying fresh greens from the store, you'll always face the issue of packaging waste. Some argue that plastic tubs at least can be recycled. In contrast, the plastic bags housing most premade lettuce mixes, and the plastic produce bags used for loose produce, such as whole heads of lettuce, cannot be recycled.

Sean Cash, Ph.D., associate professor and economist at the Friedman School of Nutrition and Science and Policy at Tufts University in Boston, says, "The processing and packaging of bagged salad would still outweigh the cost of making the plastic bags that a consumer might use at the store."19 As such, there is less packaging waste when you buy whole produce.

Triple washing ineffective

Even when the package suggests your greens have been triple-washed, you can never know for sure what may be lurking on them. Even after all that washing, germs can linger in the nooks and crannies of certain produce. Such was the case with respect to the UCR baby spinach study, where researchers observed "upward of 90 percent of adhered bacteria were observed to remain attached to and survive on the leaf surface."20

Nichola Kinsinger, Ph.D., researcher with the UCR department of chemical and environmental engineering, who was one of the study authors, said:21

"In a sense, the leaf is protecting the bacteria and allowing it to spread. It was surprising to discover how the leaf surface formed microenvironments that reduced the bleach concentration. [I]n this case, the very disinfection processes intended to clean, remove and prevent contamination were found to be the potential pathway to amplifying foodborne outbreaks."

Water use

As reported by Mother Jones, many produce companies have been triple washing their packaged greens since the 2006 spinach E. coli outbreak killed three and sickened 205.22

Gidon Eshel, Ph.D., research professor of environmental science and physics at New York's Bard College, said, "What I know is that the bagged, triple-washed variety is enormously water costly. I visited such an operation and saw for myself … the washing was just staggering."23

Given that the greens involved in the latest E. coli outbreak are grown in a water-starved area like Arizona, triple-washing "most likely becomes the single most important environmental consideration, and … becomes very difficult to defend," added Eshel.24

Ways to Safeguard Your Health When Eating Greens

While you may think washing your lettuce would eliminate the bacteria, the truth is it takes but a few cells of E. coli to make you sick. Despite the fact that rinsing your produce with water — even the brands that claim to be triple-washed — may lower your risk of illness, it doesn't eliminate your risk entirely. Washing is no guarantee you will get rid of potential toxins. Beyond that, some experts suggest using commercial fruit and vegetable washes are not much more effective than water alone.25

Although some recommend a light bleach solution, I cannot recommend bleach for household cleaning applications and even less so for food preparation. The best way to ensure the cleanliness of your food and food-preparation area is to apply common sense. Below are a few tips that will guide you in handling produce and other foods safely. Always:

Wash your hands with soap and water before handling food, and most especially after handling raw meat

Use a scrub brush to remove dirt and debris from root vegetables or any fruit or vegetable with a rough skin

Keep babies and children away from your food-preparation area

Rinse all produce, even bagged varieties, well under running water

Remember loose produce is touched and handled by many other people before it is purchased by you; wash it well before eating

When chopping more than one type of food, wash your counter, cutting board and utensils frequently to avoid cross contamination

Use separate cutting boards and utensils for raw meat

Do not prepare food for others when you are sick

Because most of the people affected by the current E. coli outbreak became ill after eating at restaurants that used bagged, prechopped lettuce in their salads,26 you can dramatically reduce your risk of infection simply by avoiding salads when dining out and by eating more meals at home. Beyond that, since raw greens pose the most risk, you may decide to cook more of your greens to reduce your risk of contamination.

Two safe options for consuming greens are steaming or using a pressure cooker — you may want to add some healthy fat to promote maximum absorption. In my opinion, your very best option is to grow your own food. Whether that be in a vegetable garden, in containers or in trays, you won't regret the time and energy you invest in cultivating healthy, homegrown food.

The good news is greens such as lettuce are among the easiest garden vegetables to grow, and they are prolific. By planting new seeds every 10 days, you can receive multiple harvests throughout the growing season. Depending on where you live, you may be able to grow certain greens year-round. If gardening is just not your thing, consider purchasing your greens from a local farmers market instead of the grocery store.