Why Do Lettuce and Spinach Keep Getting Contaminated With E. Coli?

romaine lettuce

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Key Takeaways

  • While most E. coli strains are harmless, E. coli O157:H7 can cause a severe intestinal infection in humans.
  • E. coli outbreaks are often associated with leafy greens like lettuce and spinach, partially because of the way they’re grown in soil that’s prone to contamination.
  • Most people in the United States also eat these vegetables raw, which increases the risk of getting E. coli.

Lauren Bush never expected to feel so sick from a regular spinach salad—bloody diarrhea and extreme abdominal pain forced her through multiple hospitalizations and medical consultations.

She was one of the many victims of a multi-state E. coli outbreak in 2006, which resulted in 102 hospitalizations, 31 cases of kidney failure, and three deaths.

Bush was infected by a common E. coli strain known as E. coli O157:H7, one that can cause a severe intestinal infection in humans. It’s the same strain detected in a recent E. coli outbreak linked to the romaine lettuce used at Wendy’s restaurants.

Escherichia coli (E. coli) are bacteria that live in the intestines of animals and humans. They’re mostly harmless, but certain strains like E. coli O157:H7 can cause illness in people. The most common symptoms include severe bloody diarrhea, abdominal cramps, and fever. And they usually being two to five days after consuming foods contaminated with the bacteria.

Severe cases of E. coli infections can lead to hemolytic uremic syndrome, a complication that might result in kidney failure and death.

A study from 2013 also suggested that E. coli infections are associated with a higher risk of developing high blood pressure and kidney problems later in life.

In the years following her infection, Bush has come down with similar symptoms five times. In some cases, she had to be isolated to avoid infecting other people.

“Unfortunately, once your body gets imbalanced, it can’t quite recover,” Bush said.

Why Is E. Coli Often Found in Lettuce and Spinach?

Leafy greens often fall victim to E. coli contaminations because of the way they’re grown, said Mitzi Baum, the CEO of Stop Foodborne Illness, a patient advocacy organization. Romaine lettuce and spinach are grown in the soil, which can be exposed to animal feces or contaminated water.

The produce is at risk of contamination from irrigation water especially if it's grown near animal production facilities where the animals may be infected with E. coli.

There's also a seasonal aspect to E. coli outbreaks associated with the harvest season for lettuce in different areas. For instance, the fall lettuce harvest in coastal California is associated with a higher likelihood of E. coli outbreaks.

“If the E. coli is in the water, and that water is absorbed by the raw crops and becomes part of the plant, you cannot wash that out,” Baum said. “I’m a consumer, I wash all of my produce, and I worry about it all the time.”

Another reason people are more susceptible to E. coli from lettuce or other leafy greens is that they often eat these vegetables raw. While washing the vegetables alone may not get rid of E. coli entirely, boiling or cooking them can kill the bacteria.

How to Prevent an E. Coli Infection

As scary as E. coli sounds, you don’t have to stop eating salads or burgers completely. However, you can take precautions to protect yourself:

  • Wash your hands thoroughly with soap and water before handling the vegetables
  • Wash raw vegetables before eating.
  • Cook vegetables.
  • Prevent cross-contamination by thoroughly washing hands, counters, cutting boards, and utensils with soap and water after they touch raw meat.
  • If you’re cooking meat, use a food thermometer to make sure the meat has reached a safe minimum cooking temperature.

These steps may not be enough to keep you 100% safe from risks. So, if you believe you have eaten food contaminated with E. coli, stay hydrated and seek medical care.

What This Means For You

E. coli can cause intestinal infections through contaminated food or water. Wash your hands thoroughly before and after preparing food. Make sure to wash your vegetables, or cook them to kill the bacteria whenever possible.

Correction - September 6, 2022: This article was updated to reflect the correct symptoms of Lauren Bush while she had an E. coli infection.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Multistate outbreak of E. coli O157:H7 infections linked to fresh spinach (final update).

  2. Johns Hopkins Medicine. Escherichia coli O157:H7.

  3. Centers for Disease Control and Prevention. E. coli outbreak with unknown food source.

  4. Hizo-Abes P, Clark WF, Sontrop JM, et al. Cardiovascular disease after Escherichia coli O157:H7 gastroenteritis. CMAJ. 2013;185(1):E70-E77. doi:10.1503/cmaj.112161

  5. Leonard SR, Simko I, Mammel MK, Richter TKS, Brandl MT. Seasonality, shelf life and storage atmosphere are main drivers of the microbiome and E. coli O157:H7 colonization of post-harvest lettuce cultivated in a major production area in CaliforniaEnviron Microbiome. 2021;16(1):25. doi:10.1186/s40793-021-00393-y

  6. Centers for Disease Control and Prevention. Outbreak of E. coli infections linked to leafy greens.