Could Your Salad Poison You?

Creative commons licenced image from Flickr by paulmorriss

Pre-packed salads are quick and convenient. For many of us with busy lifestyles, they're an easy way to add a little green stuff to our plates - without spending ages washing and chopping vegetables. And the range of different leaves can be appealing: if you buy a pre-mixed bag, you don't have to get a whole romaine lettuce or grow your own rocket to go beyond the iceburg lettuce.

But could your bagged salad be putting you at risk of food poisoning?

Here's a few facts:

Between 1992 and 2000, the period during which the new phenomenon of bagged salads took off, nearly 6% of food-poisoning outbreaks were associated with prepared vegetables and salads.

(from Felicity Lawrence in 'Pre-washed salad is a dirty trick', The Guardian)

In 2005, several E-Coli outbreaks in the US was linked to packaged spinach and lettuce mixes.

In 2006, three people in the US died and more than 200 people were poisoned by E coli from spinach salad leaves in 2006. The source was contamination from an intensive cattle feedlot.

At the Food Micro 2008 conference in Aberdeen, Professor Gadi Frankel (Imperial College London) said a salmonella outbreak in the UK in 2007 was traced to imported basil.

What's E-Coli?

E-Coli is carried in animal faeces, and lettuces can be contaminated by the water used for irrigation, or by water seeping in from nearby fields of cattle. It causes stomach cramps and diarrhoea, and can lead to kidney damage and death in small children, the elderly, or people with immune system deficiencies.

Even washing vegetables is often not enough to remove the dangerous bacteria:

Once processed lettuce is contaminated, it's difficult to remove bacteria, according to Mike Doyle, director of the University of Georgia Center for Food Safety.
Researchers at the center have experimented with washing lettuce contaminated with high doses of salmonella or E. coli bacteria in chlorinated water [the method used by commercial producers of bagged salads], Doyle said, but found it removed only a small amount of the bacteria.

(from E. coli Blog: Just how safe are pre-washed packaged salads?)

If you want to be completely sure you're avoiding any danger of E. coli, you're safest to buy whole heads of lettuce, remove the outer leaves and throw them onto the compost heap before washing the rest of the lettuce.

How can I avoid the risk?

Where possible, buy local, fresh salads - not ones that have been flown in from abroad in plastic bags. If you eat lettuce and other salad vegetables as soon as possible after they've been picked, they'll contain more nutrients.

If you do buy "pre-washed" salads, though, make sure you thoroughly wash them yourself to be on the safe side - just as you would wash other fruit and veg.

Do you think the bagged salad scare is overblown? Do you avoid bagged salads anyway because you think they're poor value for money? Let us know in the comments...

(Image by paulmorriss)

19 Comments

Heather on 09/22/08

Dude, you couldn't eat these days if you get all freaked about everything they make big scares over.

I'm not too concerned about E. Coli.

Chances are my salad is not infected.
Chances are I won't get E Coli.
And if I do, as I don't have a compromised immune system, chances are it will present as no more than a mild stomach bug.

Methuselah - Pay Now Live Later on 09/22/08

I read Felicity Lawrence's 'Not on the Label' a few years ago and vowed never to buy another bagged salad. Since then things have slipped a little but your post have renewed my resolve. There are so many reasons not to buy this stuff (air miles, worker exploitation, poisoning risk, putting money in the pockets of supermarkets) that I am slightly ashamed that I have been buying them again.

Trent on 09/22/08

I love salad and got the salad bags for awhile. I decided to go back to buying fresh lettuce for several reasons:

- Fresh lettuce is cheaper

- Fresh lettuce tastes better

- Fresh lettuce lasts much longer than the salad bag. The salad bags seem to need to be eaten the day they are opened, whereas fresh lettuce can be eaten over the course of 2 or 3 days if properly refrigerated.

Angie on 09/22/08

I agree with Trent. Fresh lettuce tastes better and last longer than bagged lettuce. Might take a few more minutes to get ready..but worth it.

lila on 09/22/08

I agree too... yet I'm always so lazy and never even wash my bagged salad. I guess I'm gonna start now!

Supplements on 09/22/08

I think bagged salads are a poor value for the money, but I don't think you can argue with their convenience.

lilbet on 09/22/08

Very interesting. They are convenient, but I guess, when we're not in control of the washing, we have to take a risk.

I'm not a huge fan of the taste of these bagged salads. They taste artificial to me, that's the best I can describe it.

I just got a new salad spinner at Ikea for $5 and I intend to go back to washing my own. It really doesn't take that long.

tara on 09/22/08

I am a microbiologist and actually having processed samples of bagged lettuce... GROSS! Its on par with the contamination rate of ground beef. Prebagged salads are a bacteria's dream: all that moisture to grow in. I will eat things off the floor (you really wont get sick), and have a rare steak but no bagged lettuce due to the contamination. What does that tell you?

Spectra on 09/22/08

I'm a microbiologist too and I actually don't avoid bagged salads because a) I wash all my salads in a solution of baking soda and water and b) I have a pretty good flora of beneficial bacteria living in my gut that prevent E. coli and other bad bacteria from surviving for too long.

lele on 09/22/08

sorry that is called commensals

Best Weight Loss Pill on 09/22/08

Salad is easy to arrange,i normally will prepair it by myself,never bought the salad pack, if i bought it ,i will wash once more.

thanks for sharing ya

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John W. Zimmer on 09/22/08

Heather makes a good point about your chances of getting the bug... statistically speaking your chances are low but I don't even think about that... what governs me is money... if I have little - I'll buy a head of lettuce and If I have money - I'll buy the bag of salad at Costco.

Liam on 09/23/08

I'm not overly concerned about the risk of poisoning from pre packaged salad. The risk is very low, but I would always wash fruit and veg. If you've not seen someone washing it, the chances are nobody has washed it!

Spectra on 09/23/08

I should also add that with the big spinach E. coli outbreak, washing the spinach was fairly pointless because the bacteria were sucked up into the vascular system of the plants during the irrigation process. So even if you did wash it, the germs were embedded inside the leaves.

Eileen on 09/25/08

E-Coli in salad is definitely a risk, but I think there's are risks in just about everything we eat. Think about it:

-Restaurant workers not washing their hands
-Samonella in our sunny side up eggs, undercooked chicken and beef.
-Botulism in juices and canned food
-Eating too much mercury in our fish
-Catching the flu by touching anything public and then touching your face
-Plastic packaging making us sterile

Side note: (One of my professors talked to us about a close friend of hers conducting fertility research in mice. For two years her mice stopped reproducing and she eventually pinpointed the new detergent they were using to clean cages that was causing chemicals to leech out of the plastic making all her mice sterile....plastics identicle to the ones we use to package our foods. She's been getting threats from the plastic companies ever since she's published her findings and everytime she publishes a new article, the plastic companies publish an article countering all her findings. I can't remember the last time I was this horrified...)

-Extra risk of E-Coli contamination in organic foods from the manure they use to fertilize their plants.
-All the bacteria thriving in unpasturized "raw" foods....might as well such the milk directly from a cow's poopy teat.
-Let's not forget that there is a little bit of cow pus in every glass of milk we drink...probably more in organic milk since they don't use any antibiotics (even when the cows get sick).
-And what about prions (Mad Cow Disease), you can't get rid of this no matter how much you cook your beef...and there's no cure.
-How about all the preservative in our food giving us all cancer.

It doesn't leave us much to eat. I think that all the above risks are not very high, but nonetheless very real...something will end up getting you eventually no matter how hard you try. I think people definitely overreact. They hear a 2 minute blurb about a new food scare on the evening news and become obsessive about avoiding that food. Chances are for each new food risk you hear about in the news, there a a few thousand other risks you never thought about that are more dangerous for you. Chances are you have a higher chance of dying from the common cold than you do from these food risks. That's not to say you should just ignore all this information. I just think its important to keep things in perspective and not freak out too much.

Spectra on 09/25/08

"Let's not forget that there is a little bit of cow pus in every glass of milk we drink...probably more in organic milk since they don't use any antibiotics (even when the cows get sick)."

Actually, cow's milk (just like any other mammal's milk) doesn't contain pus unless the animal is suffering from mastitis (an infection of the mammary glands). Dairy farmers do NOT sell that milk for consumption...until the animal's mastitis is cleared up, the milk goes into a disposal tank that gets discarded.

Eileen on 09/25/08

You're right Spectra, milk should not have pus if the animal doesn't have mastitis...I'm sorry, I didn't mean to be an alarmist. I'm actually a second year veterinary student at Cornell right now, before last year I had no exposure to dairy medicine... Milk is tested with a somatic cell count test before each milking. Once mastitis is detected, yes the cows are pulled from milking to be treated...but in cases of subclinical mastitis a little bit of pus does get into our milk. No milk is completely free of somatic cells. That' not to say that its bad for you (I am an avid eater of dairy products) its just something to think about. Much of meat meat we eat most definitely has some pus in it as well...

The the organic industry has an ethical dilema when it comes to cows with mastitis. Once an animal is given antibiotics it will no longer be considered organic. So what happens when a cow gets mastitis? Sometimes when the mastitis is bad enough, they sell the cow to a regular non-organic facility and lose hundreds of dollars in potential revenue. More often than not, the farmers might try to "wait it out" to see if the mastitis will resolve on its own (sometimes they will try to use natural remedies to treat the mastitis such as peppermint oil).

Thank you for your feedback Spectra, I appreciated your comment about the Ecoli actually being inside the leaves :)

Spectra on 09/26/08

My husband grew up on a dairy farm and yes, all milk has somatic cells in it, but there is indeed a threshold for true mastitis. I don't know, I guess I don't really see the harm in consuming a few somatic cells with my glass of milk, but lots of people freak when they hear that and automatically just assume it's a bad thing. It's interesting that the organic dairy farms can't give antibiotics to their cattle...I guess it theoretically makes sense, but it's a huge loss if they have to get rid of the cow just because it has mastitis.

I agree with the rest of your post though...we are becoming such an alarmist society and we freak out about every little thing. I'm thinking that as a whole, our immune systems are getting weaker as we become more and more germophobic. One of my coworkers (also a microbiologist) drinks raw, unpasteurized milk and feeds it to her 2 year old. She gets her milk from a local farmer and knows it's safe and fresh when she buys it, but when she tells people she drinks it, most people are horrified.

Eileen on 09/28/08

I eat raw milk products too, and I love them :)