Science Talk

Food Poisoning's Lasting Legacy

Scientific American Science of Health columnist Maryn McKenna talks about the new understanding that food poisoning can have long-lasting negative health effects

Podcast Transcription

Steve:           Welcome to the Scientific American podcast Science Talk posted on April 4th, 2012.  I am Steve Mirsky.  On  this episode:

McKenna:          The outbreaks of food-borne illness are less than half of the big picture of food-borne illness.

Steve:           That's journalist Maryn McKenna. Every other month she writes the Science of Health column in Scientific American magazine.  Her entry in the April issue is called "Food Poisoning's Hidden Legacy."  I called her at her home at Atlanta.


Steve:           Let's begin. I will just read the subhead of this article:  "Most people think a food-borne illness as an unpleasant few days of fever and diarrhea, but for some there may be lifelong consequences"—I am sure this is going to be a surprise to many people—"and some of these consequences are really life changing."

McKenna:          This is really striking and this is something that has really just, kind of, begun to be recognized and I agree with you,  I think this is going to be a surprise to a lot of people.  Because let's face it,  one of the reasons why food-borne illness is such a big deal in this country—and it really is a big deal, 48 million cases a year—is that, for most people, it's just not that important. You know, you eat something bad and you end up kind of being down for a weekend or a week at most and, you know, you spend a lot of time in the bathroom and you spend a lot of time being, kind of, wiped out, but then you get over it. And because it's minor, it just hasn't been that much of a public health priority.  It's kind of like colds; it's a thing that we unfortunately, sort of, accept as a cost of doing business and living in the world. Except it turns out that it's really not that minor at all.  There is this emerging understanding among a couple of researchers, who have really pretty good evidence, that in some cases, food-borne illness leaves you with stuff that is going to last your entire life and that can be really crippling as it goes along.

Steve:           Increased rates of hypertension, kidney problems, stroke, pulmonary disease ….

McKenna:          Arthritis, yeah, irritable bowel syndrome. There are people who are really—when I say crippled, I am not using that as a metaphor. I really do mean crippled; that people end up with joint problems, they end up with stuff that disrupts their digestion for the rest of their lives, they end up in some cases with diabetes that can be traced back to this infectious episode that they had. It's really troubling, and it's surprising to me when I look at this emerging understanding that it took us this long to get there.

Steve:           So, why did it take so long?

McKenna:          Well, if you think about how food-borne illness happens, you know we say 48 million people in the United States every year with food-borne illness, 128,000 hospitalized, 3000 dead, but what's going on in that is almost none of that is an outbreak.  The outbreaks of food-borne illness are less than half of the big picture of food-borne illness.  Most cases of food-borne illness are sporadic, and what that means is that they're never linked to any other cases, and they're also never linked to any particular cause; it just happens, you just go down for a weekend and then it's over and you never realize what it was that caused that.  What that means is that you never go to the doctor and therefore you never get noticed by the public health system.  No one records that you are ill; no one tries to link those sporadic cases to other cases because they don't know about them.  And since that data doesn't exist to start with, it means that the data isn't going into that larger understanding of what this might look like 10 years down the road.

Steve:           And what's changed in the last decade where suddenly this data is available?

McKenna:          There are a couple of things that have been happening. The first is a real patient movement where people just came out and said, "We're tired of this.  This is really much more serious than the authorities understand." And we can date that back to an outbreak that a lot of people have heard about which is the famous Jack in the Box outbreak in the early 1990s.  It happened mostly on the West Coast.  It came from undercooked hamburgers, and it was this country's introduction really to the food-borne organism, E. coli 0157:H7, which in its most serious manifestations kills people, mostly children, with a syndrome called hemolytic uremic syndrome in which the kidneys are overwhelmed by dying red blood cells and cease working.  So that outbreak really brought to attention in the United States that food-borne illness could be fatal. But it also inspired a patient movement largely among the mothers of those children who essentially said, "What do you mean (laughter that food could kill my child? This is not acceptable."  So, that's the first thing that happened. There are several citizen organizations, empowered patient organizations, that grew out of that outbreak that have been going now for almost 20 years and really started to change public health policy and public health attention. The other thing is that as a result of outbreaks like that being identified, researchers started to realize that they could capture those patient populations that people who were sick in these identified, very serious outbreaks and start tracking them forward in time.  That's what science calls a prospective study, and it's the strongest type of study for establishing the connection between symptoms and something that happened back in the past.  It's a much more trustworthy result if you can start with the people being ill and track them forward to their symptoms rather than if you start with the symptoms and try to figure out what happened 10 years before.

Steve:           And you talk about some of those studies in the piece; tell us a little bit about the Canadian study because that's really the biggest and the most forward looking.

McKenna:          This is a really fascinating study, and it's particularly fascinating to me because I covered the original story when it happened.  So, there was a small town—still, well there still is—a small town in Western Ontario, called Walkerton,  Walkerton, Ontario. It's out in essentially dairy cattle country, and it's really pretty.  It's in beautiful rolling hills.  It's, if you say, you know, farm town, the image that you get in your head, that's what Walkerton, Ontario looks like.  You come over these beautiful hills, there are these pretty little white and butter yellow farms and buildings. But in 2000, in the spring of the year 2000, there were very heavy rains in the area, and they washed, in the classic way the storm runoff does, they washed cattle manure into water sources in the area, and overwhelmed the aquifer to such a degree that the water treatment in the town that drew water from the aquifer and purified it, couldn't keep up. And as a result, E. coli from all those pretty cattle and all those pretty farms, got into the municipal water system, and it made essentially the whole town sick.  Now I remember driving into Walkerton, Ontario in May 2000, and as I came over the hills, I had this very strange experience because what you expect a beautiful little bucolic farm town to smell like in spring, is new grass and cow manure, and what it smelled like was bleach because every single thing in that town and every single person had been washed or swabbed with bleach.  It was the only way they could think off to kill this E. coli 0157 that was essentially everywhere.  Now, the Canadian government has a really good public health structure and they realized, early on that they needed to keep track of what was going on because there were so many people in this town who were sick.  Many more people than they actually knew about because it was fairly early on that the local hospital got completely overwhelmed.  So there were many people who during the outbreak were patients in that outbreak but were never identified as such.  So, the Canadian government, especially the government of Ontario, created a public health project to figure out from the start of this outbreak, which is now 12 years ago, what had happened to these people and what was going to happen to them going forward, and they empowered a local academic medical center to keep track of them. And ever since they have been studying what happened to all these people who had these gastrointestinal symptoms, some of which were very serious, but some of which were mild, and it turns out an incredibly high number of people who were ill have had long-term symptoms that, they're not gut symptoms.  They're things like hypertension, heart attack, stroke, congestive heart failure and kidney problems, all traceable back to that outbreak of E. coli back in 2000.

Steve:           Do we have any idea why those other sequlae erupt because of the food poisoning?

McKenna:          Well, this is what people are now just trying to work out.  So, the first thing that's happened is that, you know—over these past 10 years or so—is that people have presented pretty good proof, these researchers who were empowered by the Ontario government, had presented pretty good proof that there is a tie that they can establish between that E. coli infection and what's happened to people since. And the next question is, well, why did that happen?  And what they're thinking about now is that you know, we already know that the most serious complication of E. coli 0157 infection at the time is this very serious issue, hemolytic uremic syndrome, which overwhelms the kidneys and causes kidney failure.  So, it seems that what's going on there is that the toxins produced by E. coli 0157 are disrupting blood cells, disrupting the circulatory system, and overwhelming the kidneys.  So, it looks like that disruption, that insult to the circulatory system, is not just a temporary thing, but in fact has a long time consequence, and so people who might not have been sick enough to have hemolytic uremic syndrome still had some insult to their circulatory system that going forward created high blood pressure, created an increased risk of heart attack, created an increased risk of stroke.

Steve:           And we have this condition called reactive arthritis, which sounds like there might be an autoimmunity component.

McKenna:          Right.  Now this is caused, the strongest link is to a different organism; all of that circulatory stuff I was just talking about has been linked to infection with E. coli, particularly E. coli 0157 and other E. coli that are toxin producing.  Now the reactive arthritis cases, these are interesting because they mostly seem to be linked to infection with salmonella, an incredibly common food-borne illness.  And I talk in this column this month about a girl who is now in her teens, who was one of 50 people who were known to be sickened in the United States, 10 years ago now, by melons that were imported from Mexico and were contaminated with salmonella.  The melons would have been contaminated on their surface and then at some point when they were sliced into, the salmonella got into the flesh of the melon, people ate it and they got sick.  This girl, Dana Dziadul, started to complain that her joints hurt as she was growing up and her mother Colette, thought "Oh, it's just growing pains; oh, you know, things are going to catch up." And she took her periodically to doctors and the doctors said the same thing, the doctor said, "She'll grow out of it," and it turned out she wasn't growing out it because it wasn't just growing pains, it was arthritis. And when Colette went back and checked Dana's medical records, it turned out that when she'd been in the hospital only a couple of days when she was three years old, in the midst of the salmonella outbreak, she was already complaining of things hurting.  So, Colette and some of these empowered patient organizations that I told you about, particularly one called STOP Foodborne Illness—used to be called Safe Tables Our Priority. They started surveying people who'd been in recent outbreaks and found a really remarkable rate of reactive arthritis.  So, from those patient observations, there's starting to be this understanding that for reasons that people have not yet worked out on an individual, sort of, mechanistic level, that that infection with salmonella in the gut—which we all know now is, sort of, our second immune system—is doing some permanent disruption in a, kind of, autoimmune sense that sets people up for arthritis down the road. And you can see, if you think about this, that this not a connection that people would intuitively have made because salmonella is a gut infection, and here we're talking about joint disruption. But the observations are pretty indicative now that there really is some connection.

Steve:           So, there are two obvious questions now.  What do we do as individuals to, I mean, nobody wants to get food poisoning because just the event itself is really horrific, but you certainly don't want to get it if there's the possibility of any of these other things happening afterwards.  So, what can the individual do, and then what do we do as a country to try to limit these kinds of outbreaks?

McKenna:          These are really the essential questions.  So, the first thing is, I think, that this makes food-borne illness a much more serious problem.  I mean, it ought to make it a higher priority, both on a country level, as a public health issue, but it ought to make it a higher priority for all of us.  I think most people are pretty good about the things that they do to try to protect themselves from food borne illness; most people, you know, think about the five second rule—which of course, you know, is not something that you're supposed take seriously—but what I mean is most people don't, you know, eat something that's lying on the floor; most people wash their produce; most people try to keep raw meat and vegetables separate; most people wash down their kitchen pretty well. But the thing is this should be just, kind of, a reminder to us to take all of that much more seriously because if you do get food-borne illness, it's not necessarily something that's only going to put you down for a week; it's something that could have really serious consequences for you, for your family, for your children years down the road. And you know, it's always hard for us to keep in mind when we do something that it might have consequences later. That's why people are not good about things like sticking to a diet or wearing their seat belts or wearing sunscreens. But this is another reminder that things that we do have long-term consequences.  The second issue is what does this mean for us, as a country?  And there's both, sort of, a short-term question and a long-term question embedded within that.  The short-term question is should we be doing more, when we know that there are food-borne illness outbreaks, to keep track of people afterward?  That's often very hard because, and the fact that's it's hard is one reason why this connection hasn't emerged until now; is because when people are in an outbreak, it's actually kind of unusual that they're all in the same place, as happened in Walkerton, Ontario.  Our food production system is so complicated that when you have a nationwide outbreak—like those 50 people with the melons that was the outbreak that Dana Dziadul was made sick in—there might be two people in one state, three people in another state, another person across the country; all of those people would have been registered by different state health departments and the health department only cares about them when they're sick.  They have never had a mechanism for keeping track of those people years later.  Well, now we need, I think, to start thinking about keeping track of all those people for years, to see what happens to them, and that is probably not the responsibility of an individual state health department because people move.  It may be something that the federal government has to start thinking about—should they be creating registries for food-borne outbreaks?  And the larger question is, if we don't start taking care of this, what is the cost down the road? Another reason why food-borne illness has never really been a major public health priority—I mean we keep track of it, we count that there are 48 million people a year, but we, our prevention efforts are probably, kind of, down there on the priority scale compared to things like cancer or HIV.  If we start understanding that the cost of an individual case of food-borne illness is not somebody feeling sick for a couple of days or two or three days of lost productivity, but instead tens of thousands of dollars because someone has to be treated lifelong for arthritis or for hypertension or a heart attack or a stroke, in my mind that means that we should be moving this up the scale of priority for our public health system; because if we don't, the costs to society are going to be so much greater than we ever really realized.

Steve:           Maryn McKenna's science of health column in the April Scientific American is called "Food Poisoning's Hidden Legacy."  Maryn, always great to talk to you.  Thanks very much.

McKenna:          Oh thank you.

Steve:           Maryn's column is also on our Web site,  We'll be right back after this word from Kerri Smith at the Nature Podcast.

Kerri Smith:  On the Nature Podcast this week, we meet a new species of giant feathered dinosaur, discuss financial incentives in science and track down a disease blowing in the wind.

Steve:           Just go to  That's it for this episode of the Scientific American podcast.  Get your science news at, where you can check out Kate Wong's April 2nd observations blog item on the discovery that our ancestors tamed fire a million years ago, which led us to the April 4th news item titled "Flame Retardants May Create Deadlier Fires"—well that's progress.  And follow us on Twitter where you'll get a tweet every time a new item hits our Web site.  Our Twitter name is @sciam.  For Scientific American's Science Talk I am Steve Mirsky.  Thanks for clicking on us.

Share this Article:


You must sign in or register as a member to submit a comment.

Starting Thanksgiving

Enter code: HOLIDAY 2015
at checkout

Get 20% off now! >


Email this Article