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  • Dimitrios Douros

    The Cross-Contamination Myth-Buster!

    Dimitrios Douros
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    Reviewed and edited by a celiac disease expert.

      Journal of Gluten Sensitivity Autumn 2014 Issue

    Photo: CC--Rex Hammock
    Caption: Photo: CC--Rex Hammock

    Celiac.com 08/22/2016 - The issue of cross-contamination keeps coming up in articles, conferences, blogs and every other venue in which celiacs discuss ways of living with our disease. For all the talk there has been precious little, if any, thoughtful analysis, so I felt it was time for one. Some will appreciate this analysis—others will not. For reference, I don't work for the food industry in any way, shape or form, so I'm not presenting arguments to help anyone make money. I just think that the way gluten permeates our food culture, we celiacs have become overly cautious and worried about where the next molecule of gluten may be hiding, ready to attack us, and as a result walk around in constant fear, significantly degrading our overall quality of our life and doing more harm to our health through stress than a rare, chance episode of cross-contamination might actually do.

    Using the FDA's 20ppm limit as the definition of gluten-free, and some simple, first grade arithmetic, I want to look at the cross-contamination issue and see what's worth worrying about and what's not.

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    Because cross-contamination is a situational, process-related issue, it is best to separate the issue into categories that relate to the situation: a) at home, B) in food production lines shared with gluten products, c) at the prepared food counter in the local grocery store, d) in restaurants.

    What's E.coli Got to do With It?
    Cross-contamination at home is mostly an issue for someone just starting out on a gluten-free life and for those 'blended' families that have some individuals on a gluten-free diet and the rest of the family not.

    There have been many posts over the years with this sentiment: "I just got diagnosed with celiac disease, I have started on the gluten-free diet and other celiacs are telling me to get rid of most of my cooking utensils, especially wooden spoons, plastic spoons, basting syringes as well as brushes I use with oil and butter."

    The concern behind this statement is that porous wood and scratches in plastic spoons and syringes or the hairs of a brush can harbor gluten particles that can contaminate our food. A reasonable sounding argument on the face of it, but one that has absolutely no merit when examined in the light of science and reason!

    E.coli found in beef and salmonella found in chicken are living nasty organisms that multiply and spread and can cause health problems from mild GI upset to death in some cases. And yet there has never been a case of someone throwing away their kitchen utensils after cooking chicken or beef. The utensils—wood, plastic or otherwise—get washed and re-used. If we trust proper washing to get rid of nasty, living, growing organisms that can kill us, there is no reason to doubt that the same proper washing can get rid of some particles of gluten—a non-living, non-growing, non-spreading food ingredient.

    Playing the devil's advocate, let's assume that our washing left behind a thin layer of wheat flour on a wooden spoon—certainly an amount so small that cannot be seen, else it would have been wiped away. How much flour is that? The flour from one fifth of a grain of wheat is enough to completely cover the spoon. One fifth of a grain of wheat is 16mg of wheat; of which no more than 3mg is gluten. So let's assume we use that wooden spoon to prepare pasta in a 1-quart pot and all the flour on the spoon dissolves into the water with the pasta. That's 3mg of gluten in 1,000grams of water (1-quart = 1,000g of water). That works out to around 3ppm gluten in the pot. That is well below the 20ppm definition of gluten-free in the new FDA regulations; it is actually below any level today's best science can even measure! What's more, since we assumed that ALL the flour on the spoon dissolved into the water, the spatula is from now on, forever gluten-free, just as un-contaminated as a brand new spatula from the store!

    Moral of the story: either the washing will remove the gluten from the utensils, or the gluten left over will be below the 20ppm limit in the first food cooked with that utensil and leave the spoon completely uncontaminated ever after. So if you want to use gluten as an excuse to get some new cooking utensils, that's OK, but there is certainly no cross-contamination reason to do so. If you are really concerned, take all your utensils, put them in a pot of boiling water for 10 minutes and you're done! After all, that's how hospitals used to sterilize syringes before throw-away ones became the norm.

    Additionally this argument would indicate that a family that cooks both gluten-free and non-gluten-free could use one set of utensils as long as they get washed after every use. To feel more comfortable, one could use two sets of utensils, one for gluten-free the other for the rest.

    That's False Advertising—I'm Suing You!
    Cross-contamination concerns for foods from shared lines come up as we read food labels that say: "Prepared on a production line that also processes wheat and tree nuts."

    A couple of things to start the discussion: Making customers sick is a bad business plan, the only thing worse is having customers sue for severe illness or death. For these reasons food companies that use allergens in their products - wheat, milk, soy, nuts, shellfish, etc., take the precaution of cleaning their production lines between runs of different products to avoid the very cross-contamination that could sicken or kill their customers. However, in our extremely litigious society, even when a company knows its production line is clean and free of cross-contaminants, it is safer to simply slap the label: "Prepared on a production line that also processes wheat and tree nuts" on the product and completely avoid any nuisance lawsuit.

    Of course this leaves all of us celiacs scratching our heads trying to decide whether it's OK to consume such a product or not. Opinions vary; for my part, I note the label, keep it in mind, but operate on the basis that the company does have a standard process for cleaning their equipment between product runs.

    With that assumption, the only chance of cross-contamination is in the first few batches of the product to go through the line, batches that most, if not all, manufacturers test and discard if found to be cross-contaminated. Even if such a 'spot' contaminated batch made it through to the market the analysis would follow along the same lines as all other cases in this article. The amount of wheat flour (and therefore gluten) that is left on the processing line must be too small to even be seen, otherwise it would have been wiped away. That small amount spread over several 'units' of the product could only result in a few ppm gluten for each 'unit' of the product. Certainly not a cross-contamination concern.

    There's Gluten in Salmon! Really?
    Cross-contamination at the grocery store; primarily a problem in any of the many grocery stores that prepare foods on premises, like sushi and salads or getting fresh-sliced cold-cuts at a deli.

    Pick up a tray of salmon or tuna sushi - nigiri, sashimi, maki—and the ingredient list includes wheat, but the person that prepared it says they don't use wheat. Pick up a salad that obviously has no wheat in it and yet the label lists wheat as a potential allergen. What is going on?

    The most probable culprit in all such cases is the packet of condiments 'on the side'. Sushi almost always includes a sealed soy sauce packet or two for people to use if they want. As we celiacs know most soy sauce contains wheat so, the label on the entire sushi container—which includes the soy sauce packets—lists wheat because of the soy sauce. Skip the soy sauce and enjoy your gluten-free sushi! Same argument with a salad—if wheat is listed as an ingredient but there is no obvious wheat in the salad (croutons, bread, etc.) then the wheat listed is most probably in the dressing offered on the side—skip the dressing.

    Getting fresh cold-cuts at a deli to make sandwiches with your favorite gluten-free bread can raise the question of cross-contamination at the slicer from cured meat products that may contain gluten. First, any reputable deli wipes down their slicer between orders. To add a level of safety, explain the cross-contamination concern and ask the person preparing the order to set aside the first 5 slices—they will always oblige. Any residual gluten will stick to the first few slices and the rest will be fine.

    A Gluten Fog: Your Local Pizzeria—Not That Scary!
    We're all getting used to pizza places that have become enlightened enough to add gluten-free pizza options to their menu. They prepare gluten-free dough and cook the pizza in a dedicated corner of their oven or on baking sheets reserved for gluten-free pizzas. Giving them the benefit of the doubt that they spread out the toppings with no cross-contamination—which is easily checked by a few questions—this leaves one more cross-contamination concern. In 'high end' pizza places that roll their own dough for the regular (wheat) pizzas there's flour dust in the air. It would seem to be a valid cross-contamination concern, but the numbers are again, against it—unless the flour dust in the kitchen is so thick you can't see from one end of the kitchen to the other—not likely because flour dust that thick is a fire hazard!

    So the analysis again reveals a non-issue: the amount of flour dust that lands on a 10" pizza is less than one wheat grain's worth. That's 65mg of wheat, worst case that is 10mg of gluten which translates to less than 10ppm for the entire 10" pizza, again well below the 20ppm definition of gluten-free in the new FDA regulations! So if you're feeling GI distress after eating your favorite gluten-free pizza at your favorite pizzeria, it's probably the pepperoni!

    Salads at a restaurant are the next big concern because of the increasing tendency to see croutons or pita wedges as part of the salad. Of course you ask for your salad without the gluten item. And wouldn't you know it when the salad comes you see a big pita wedge right on top! Of course you ask that they take it back and bring you one without pita. And you wonder—did they make a new one or just serve you the old one after taking the pita off? Or maybe it's a business lunch with an important client and you don't want to make a fuss and don't even ask for a new salad. This is where my analysis goes a bit too far for some. I will remove the pita or pick around the croutons and eat the salad without a worry about getting 'glutened'. In my scientific brain the case is quite simple and clear: the thing we miss the most about gluten is its sticky property—it's a glue that sticks things together, and makes it possible to have light, airy, crusty baguettes to die for! Well, that same great property is what gives me the confidence to eat that salad. During baking, the gluten is completely bound up in that pita or in the croutons—it is not going to come loose just to contaminate me. It has not been laying in wait for the opportunity to be put on a celiac's plate and launch an attack on my villi—it's just not going to happen, nature does not work that way.

    So, worry a little less and enjoy a lot more! I leave you with this empirical fact: There was a report back in the late '90s about a 10-year research program that went around the world interviewing people that were in their 90's to try and find a common thread to their longevity. Every factor was considered, food, smoking, physical activity level, genetics, drinking—everything. Once all the data was analyzed there was one and only one, crystal clear, common factor among all these people: they knew how to let go of worry, stress, loss, pain. Regardless of what life threw at them, they moved past it to the other side and kept on going. Don't let unfounded, irrational fear of gluten rob you of your life—move past it!

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    I think this is a generalization depending on how sensitive the person is to the gluten. I think making a generalization like this is the problem and why most people get sick in a home or public setting. I think these generalizations are the problem with the doctors, non celiacs and celiacs, there is so much judgement and assumption with out knowing how it impacts the people who are impacted by what their celiac is. I think it is great that you did some math on it but I think this is your experience and not the experience of others. I am super sensitive and these opinions would set me up for a 3 month health issue. I would not call this a myth-buster I would call this your experience with your struggle.

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    The real concern with cross contamination is in a situation, like a restaurant or food preparation, where an entire gluten bit gets in your food. For example, a bunch of bread crumbs fall in your plate or in food manufacturing there is significant residue from a previous food process. No one cares whether or not someone washed a spoon well enough to put in a pot of boiling water! We´re also concerned about the cumulative effects of multiple exposure during the day - fries that came from the same oil that breading is floating in coupled with crumbs from tongs used to grab bread and our piece of chicken off the grill and breathing in the flour that is floating in the air at that pizza place (breathing it in goes down your throat to your stomach btw) - things like that. Your example of e-coli is ludicrous! Bacteria die after very short time when they don´t have proper heat and moisture so really, once a utensil is dried completely the chance of getting sick is gone BUT gluten doesn´t die - the risk is always there until it bio degrades, which takes ages! Further, sushi is a bad example as most does have wheat flour in the rice to add stickiness and pliability.

    I really think you´re grasping at straws here for content...the only redeeming part of your article is that it may put someone´s mind at ease about using someone else´s dishes. good job on that.

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    "The FDA came to a different conclusion in its analysis: It found that for the most sensitive people, intestinal damage begins at 0.4 milligrams of gluten per day (1/200th of a teaspoon of flour or 1/8,750th of that slice of bread), while symptoms begin at 0.015 milligrams of gluten per day (less than 1/500th of a teaspoon of flour or 1/233,333th of that slice of bread). The agency based those conclusions on various studies, including two case studies involving recurrent symptoms in people who consumed wheat-based communion wafers once each week." https://www.verywell.com/how-much-gluten-can-make-me-sick-562489


    You cannot boil away gluten like a germ. Not all companies are careful about cleaning equipment between runs. A company is not required to test food labeled gluten free although many do. Also read about The Gluten Contamination Diet that get rid of trace amounts of gluten and help heal some who were thought to have refractory celiac disease.

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    I think this is a generalization depending on how sensitive the person is to the gluten. I think making a generalization like this is the problem and why most people get sick in a home or public setting. I think these generalizations are the problem with the doctors, non celiacs and celiacs, there is so much judgement and assumption with out knowing how it impacts the people who are impacted by what their celiac is. I think it is great that you did some math on it but I think this is your experience and not the experience of others. I am super sensitive and these opinions would set me up for a 3 month health issue. I would not call this a myth-buster I would call this your experience with your struggle.

    I agree completely. I am also super sensitive and even drinking wine that has been brewed in oak casks or had wheat in the purifying process has made me ill.

    The downside of an easy contamination like this is being ill for months, needing to go back on iron tablets and feeling annoyed that people who ´minimize´ the risk of cross-contamination don´t help those of us who are very sensitive. This isn´t just an allergy - this is an auto-immune disease and the effects of contamination really aren´t worth the risks. It´s not as if you just feel ill for a couple of days - it´s actually damaging your body, causing the villi to atrophy and nutrients not to be absorbed. People often play coeliac disease down and that gives the wrong impression to many of those who believe it´s just a faddy diet and one crumb won´t hurt - well actually it can and does, maybe not to all coeliacs but certainly for a percentage of them. Would one drop of rat poison hurt? Quite possibly and most would choose not to take the risk. I liken it to a crumb in those of us who are super-sensitive.

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    It is 100% IRRESPONSIBLE, DANGEROUS, and DAMAGING to the Celiac community to tell them that cross contamination isn't a big deal, that it's okay to pick croutons off a salad, that all manufacturers have high quality cleaning practices and test their products.


    We all have different sensitivity levels when it comes to outward symptoms. However, I know many many Celiacs who react to less than 20ppm. Shared utensils, flour in the air, croutons in salads – all of these things have made many of us sick. This guy doesn't seem to be that sensitive. He is not a myth buster. He is writing about his sensitivity in the gluten free world. He does not represent us as a whole and should not be publishing an article like this claiming that he does.


    Some Celiacs out there will read this article and trust it because they want it to be true. They want life to be easier. And then they will go to a restaurant and tell their friends and the waiter that cross contamination isn't a big deal. And that hurts all of us. That creates more people who will tell me that I'm crazy or overreacting, when in reality I'm right and desperately trying not to get sick. This article and its assumptions are insulting to the Celiac community.


    My full response:


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    That was a terrific article. As someone who is consumed daily with this subject (I am gluten-free, my daughter is gluten-free and I run a gluten-free marketing agency), it is helpful to see that someone else shares my opinion about cross contamination. We order cautiously in restaurants but eat in them often. We buy tons of gluten-free products but also buy those that are manufactured on equipment that may have seen some wheat in its day. The article is thoughtful and well researched.

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    The author is lucky that he is not sensitive to trace amounts of gluten, but he does not speak for all celiacs. I agree with Anne and Jessica above. Quote all the numbers you want but my body knows when it´s been glutened and I´m sick of hearing that my symptoms are a "myth." It's dangerous as well as insulting.

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    I do not like this article at all. As mentioned by others, each person has a different tolerance, and for any amount of gluten there is someone somewhere who will react. Next is the fact that comments are based on the 20ppm that the FDA just made up. Finally, there is no comparison between removing a pita from the top of a salad and eating around croutons. In some cases (and you can most likely tell visually), the pita did not significantly affect the salad. Every crouton has lots of crumbs. One who can eat around the croutons in a salad and not worry about it at all is probably not sensitive to gluten at all.

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    I agree with him completely. I have had celiac for 25 years and eat out frequently. I order all gluten-free and rarely have problems with cross contamination. I also agree stress is one of the biggest triggers. Relax, enjoy and don't worry about every little thing is the best treatment.

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    I agree. Life is hard enough as a celiac without drama. I stopped going to gluten-free meetings locally because newcomers met fear that rose to the level of hysteria. Don't eat blue-cheese because it originally came from bread mold? Don't drink Scotch because it is fermented from barley? Really? Does science matter?

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