Is bagged lettuce worth the safety risk?

Pre-bagged lettuce is among the biggest culprits when it comes to food poisoning. It faces multiple contamination points at farms and in factories. Certain populations may want to avoid it in favor of unbagged lettuce.

Written by and verified by the Research Team. Last updated on Jun 28, 2018.

Why is this an issue?

A nation-wide romaine lettuce recall ended in May of 2018, and it was a really big deal.

In fact, it was the biggest multistate outbreak since 2006. Nearly 200 romaine lettuce eaters got sick by the time everything was over. Half of them were hospitalized, and five people died.

Note: These are the final numbers at the end of the recall; the video numbers derive from the statistics during the recall at the time of video production.

So … is bagged lettuce safe? Ever since the recall, triple washed lettuce just doesn’t seem as hygenic as it used to. Let’s quickly go over the evidence. We’ll start with some reasons to be alarmed, then balance it out with reasons not to freak out, and finally go over some practical tips.

Reasons to be alarmed

1. Lettuce outbreaks happen a lot

Leafy veggies were responsible for 22 percent of foodborne illnesses in the last decade, the same as all meat and poultry combined.

For comparison, fish and shellfish were at just six percent. That includes things like suspect grocery store sushi and raw oysters. These kinds of foods, along with burgers and raw eggs, historically have been associated with food poisoning. But leafy veggies have caught up in the past few years.

Keep in mind that many cases of leafy-green food poisoning probably aren’t even reported, since people are more likely to suspect the meat than the lettuce when eating a mixed meal.

2. Lettuce is especially susceptible to bacteria

Leafy greens grow close to soil, so they’re pretty easily contaminated. Chlorine washes are meant to kill these pathogens, but studies have shown that these sprays are only partly effective.[1]

3. There are many possible contamination points

Possible contamination spots start at the farm, and continue on at the factory.

Contamination can come from just one farm worker not washing their hands, and other contamination routes abound (such as birds flying over head and pooping on crops, dried manure blowing in the wind, or even feral pigs roaming into the field).[2][3][4]

Once at the factory, cutting lettuce causes liquid to be released, causing bacteria to stick to the plastic bag. This can trap bacteria onto the lettuce so strongly that it can’t be washed off.[5]

Also, greens from multiple farms are often bagged in the same factory, which increases the odds of cross-contamination.

Unfortunately, the infectious dose of E. coli O157 appears to be very low - probably fewer than 100 bacteria.[6]

4. Food poisoning may be bad for overall health

Evidence has started to suggest long term impacts of food poisoning, including increased chances for reactive arthritis and inflammatory bowel disease.[7]

This could be due to certain bacterial toxins, which can cause the body to attack its own gut lining.[8]

Reasons not to freak out

1. Specific populations are most at risk

When confronted with a bacterial toxin, those who are physiologically susceptible will more often get sick. So cases that end up at the hospital often (but not always, by any means) include certain special populations.

These populations are those with compromised immune systems, elderly people, children, and pregnant women.[9][10] That’s a lot of categories, though. So if you have friends or family who might be susceptible, that’s a factor to take into consideration when choosing produce at the grocery store.

2. Not everyone reacts the same

A healthy and diverse gut microbiome might actually help crowd out bad bacteria.[11][12] 

It’s impossible to predict whether or not your specific gut enviornment is resilient, and hence less likely to be severely impacted by these sorts of bacterial toxins. But (ironically) eating a diet rich in leafy greens and other produce may help fortify your gut against gut inflammation, which can enable bacterial toxins to enter the bloodstream more easily.[13][14]

Practical tips

A few simple tips can help you avoid unnecessary risk.

First, use your lettuce earlier than the use-by date, thus limiting the time in which bacteria can multiply.

Second, avoid sprouts. While not technically a leafy green, sprouts are probably the riskiest plant food, since they’re grown in warm and wet conditions. They’re basically germ incubators, and have been responsible for many outbreaks over the past two decades.

Third, don’t bank on organic greens being outbreak-proof. There’s not enough data yet to compare organic to conventional safety, but the biggest study to date found 18 organic food outbreaks in a 12 year period.[15] Some of these can be big. Like back in 1996, juice from the organic company Odwalla was behind a big outbreak that made 66 people sick and killed a 16 month old girl.[16]

Lastly, think about your own personal risk tolerance level. Some people are comfortable with the overall low odds of serious food poisoning complications. But others aren’t, especially since the risk is mostly avoidable if you choose un-bagged lettuce instead.

Bottom line

Bagged lettuce is quite susceptible to contamination, in both farms and factories. This has led to a large number of food poisoning outbreaks, even compared to usual suspects like seafood, meat, and eggs.
Infection with E. coli O157 from bagged lettuce often leads to hospitalization, and can even lead to death. Those with health conditions, or who are risk averse, may want to avoid bagged lettuce in favor of loose lettuce.


  1. Highmore CJ, et al. Viable-but-Nonculturable Listeria monocytogenes and Salmonella enterica Serovar Thompson Induced by Chlorine Stress Remain Infectious . MBio. (2018)
  2. Park S, et al. Generic Escherichia coli contamination of spinach at the preharvest stage: effects of farm management and environmental factors . Appl Environ Microbiol. (2013)
  3. Solomon EB, Yaron S, Matthews KR. Transmission of Escherichia coli O157:H7 from contaminated manure and irrigation water to lettuce plant tissue and its subsequent internalization . Appl Environ Microbiol. (2002)
  4. Jay MT, et al. Escherichia coli O157:H7 in feral swine near spinach fields and cattle, central California coast . Emerg Infect Dis. (2007)
  5. Koukkidis G, et al. Salad Leaf Juices Enhance Salmonella Growth, Colonization of Fresh Produce, and Virulence . Appl Environ Microbiol. (2016)
  6. Coia JE. Clinical, microbiological and epidemiological aspects of Escherichia coli O157 infection . FEMS Immunol Med Microbiol. (1998)
  7. Ternhag A, et al. Short- and long-term effects of bacterial gastrointestinal infections . Emerg Infect Dis. (2008)
  8. Rosser EC, Mauri C. A clinical update on the significance of the gut microbiota in systemic autoimmunity . J Autoimmun. (2016)
  9. Lund BM, O'Brien SJ. The occurrence and prevention of foodborne disease in vulnerable people . Foodborne Pathog Dis. (2011)
  10. Kendall PA, Hillers VV, Medeiros LC. Food safety guidance for older adults . Clin Infect Dis. (2006)
  11. Rolhion N, Chassaing B. When pathogenic bacteria meet the intestinal microbiota . Philos Trans R Soc Lond B Biol Sci. (2016)
  12. Coyte KZ, Schluter J, Foster KR. The ecology of the microbiome: Networks, competition, and stability . Science. (2015)
  13. Holscher HD. Dietary fiber and prebiotics and the gastrointestinal microbiota . Gut Microbes. (2017)
  14. Cardona F, et al. Benefits of polyphenols on gut microbiota and implications in human health . J Nutr Biochem. (2013)
  15. Harvey RR, Zakhour CM, Gould LH. Foodborne Disease Outbreaks Associated with Organic Foods in the United States . J Food Prot. (2016)
  16. Centers for Disease Control and Prevention (CDC). Outbreak of Escherichia coli O157:H7 infections associated with drinking unpasteurized commercial apple juice--British Columbia, California, Colorado, and Washington, October 1996 . MMWR Morb Mortal Wkly Rep. (1996)