WITH the recent recalls of millions of gallons of ice cream as well as several tons of hummus, pine nuts, frozen vegetables and various meat products, you might think the American food supply is an unholy mess. It’s not. It’s arguably the safest in the world.
Yet despite continually improving processing methods and quality controls, the number of cases of food-borne illness has remained stubbornly high since the 1990s, with the incidence of people getting sick from some pathogens increasing. Some experts wonder if we’ve reached a point of diminishing returns in food safety — whether our food could perhaps be too clean.
Industrial food sanitation practices — along with home cooks’ antibacterial veggie washes, chlorine bleach kitchen cleaners and sterilization cycle dishwashers — kill off so-called good bacteria naturally found in foods that bolster our health. Moreover, eliminating bad or pathogenic bacteria means we may not be exposed to the small doses that could inoculate us against intestinal crises.
“No one is saying you need to eat a peck of dirt before you die to be healthy,” said Jeffrey T. LeJeune, a professor and head of the food animal research program at Ohio State University in Wooster, Ohio. “But there is a line somewhere when it comes to cleanliness. We just don’t know where it is.”
The theory that there might be such a thing as “too clean” food stems from the hygiene hypothesis, which has been gaining traction over the last decade. It holds that our modern germaphobic ways may be making us sick by harming our microbiome, which comprises all the microscopic beasties — bacteria, viruses, fungi, mites, etc. — that live in and on our bodies.
Research so far has focused primarily on the detrimental effects of cesarean births and not breast-feeding, which may inhibit the formation of a robust microbiome, and the use of antibacterial soaps and antibiotics, which diminish the microbiome once it is established.
A result is an immune system that essentially gets bored, spoiling for a fight and apt to react to harmless substances and even attack the body’s own tissues. This could explain the increasing incidence of allergies and autoimmune disorders such as asthma, rheumatoid arthritis and inflammatory bowel syndrome.
There is also the suggestion that a diminished microbiome disrupts hormones that regulate hunger, which can cause obesity and metabolic disorders.
When it comes to food-borne illness, the idea is that fewer good bacteria in your gut means there is less competition to prevent colonization of the bad microbes, leading to more frequent and severe bouts of illness.
Moreover, your underutilized immune system may lose its ability to discriminate between friend and foe, so it may marshal its defenses inappropriately (e.g., against gluten and lactose) or not at all.
All of this is hard to prove. While there has been some research to support the effectiveness of consuming harmless bacteria, known as probiotics, in reducing the likelihood of gastrointestinal infection, there are ethical issues involved in dosing humans with known dangerous pathogens like salmonella and listeria.
But animal experiments have lent some credence to the theory. Researchers at Texas Tech University in Lubbock have found that guinea pigs fed less virulent strains of listeria are less likely to get sick or die when later fed a more pathogenic strain. And anyone who has visited a country with less than rigorous sanitation knows the locals don’t get sick from foods that can cause tourists days of toilet-bound torment.
“We have these tantalizing bits of evidence that to my mind provide pretty good support for the hygiene hypothesis, in terms of food-borne illness,” said Guy Loneragan, an epidemiologist and professor of food safety and public health at Texas Tech.
This is not to say we’d be better off if chicken producers eased up on the salmonella inspections, we ate recalled ice cream sandwiches and didn’t rinse our produce. But it raises questions about whether it might be advisable to eradicate microbes more selectively.
It is worth noting that serious food-borne diseases — the ones that make it into the news, like listeria, salmonella, E. coli, cryptosporidium and campylobacter — are mainly diseases of immuno-compromised populations. And that’s getting to be a significant number of people, thanks to our aging population.
“It’s a cruel reality that anyone 55 and older is potentially immuno-compromised,” said Haley Oliver, assistant professor of food science at Purdue University in West Lafayette, Ind. Also included are young children, pregnant women, the estimated 1.2 million people with H.I.V., cancer patients, organ recipients and anyone who has been prescribed a lot of antibiotics.
The three people who died after eating listeria-laced Blue Bell ice cream, prompting a recall of the company’s product last month, ate it while inpatients at a hospital in Wichita, Kan. Local health officials said listeriosis may have contributed to but did not cause these people’s deaths. Seven more people were sickened nationwide.
That leaves millions who, experts said, ate the remaining five years’ worth of ice cream included in the recall and probably didn’t have so much as a stomach cramp. Research shows listeria is commonly found in dirt and in households, particularly in rural communities, and those who come in contact with it often remain asymptomatic.
“When disease happens you have to have a perfect storm of enough of the pathogen present in the food, the person ate enough of that food and that person was immuno-compromised,” said Dr. Oliver. “But because of the hygiene hypothesis we may be becoming a more naïve or vulnerable population.”
She’s not so worried for herself since she travels widely on U.S.A.I.D. missions to places with abundant food-borne pathogens like India and Afghanistan. She and other food science experts interviewed said they ate potentially disease-carrying foods like sushi, medium-rare steaks and items that they dropped briefly on the floor (invoking the five-second rule).
“It’s a personal trade-off,” said Martin Wiedmann, professor of food safety at Cornell University. “If it’s something I really like, I might be willing to take more risk,” which in his case is eating raw oysters, albeit from very cold waters.
But risk is difficult to gauge because of factors like age, illness, popping too many antibiotics, psychological stress or possibly too clean a diet.
On the upside, efforts like the Human Microbiome Project and Earth Microbiome Project are using advanced methods to identify all the microbes living on and within us, as well as in the soil and also in foods, to see how all those invisible organisms interact to promote or inhibit disease.
“It’s exciting because methodological approaches to getting this data are almost outpacing our ability to analyze it,” said Dr. LeJeune at Ohio State. “We’re going to have these humongous data sets that we’re going to have to sift through and figure out what it all means.”