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  • Jefferson Adams
    Jefferson Adams

    The Gluten Contamination Study We've Been Waiting For

    Reviewed and edited by a celiac disease expert.

      Do you really need that dedicated gluten-free toaster and dedicated flatware? A new study says you might not.


    Caption: Image: CC BY-SA 2.0--threefingeredlord

    Celiac.com 10/14/2019 - One of the big debates among people with celiac disease concerns how vigilant celiacs need to be to make sure they avoid gluten. What does science say about gluten contamination in three common scenarios? How careful do you need to be about gluten contamination?

    For example, how likely are you to get gluten over 20ppm if you share a toaster, pasta water, or slice a cupcake with the same knife used to cut a non-gluten-free cupcake?

    A team of researchers recently set out to assess three common scenarios where people with celiac disease might reasonably fear gluten contamination. How did the actual risk for each situation measure up?

    • Scenario 1: Water used to cook regular pasta is reused to cook gluten-free penne and fusilli. The gluten-free pasta is then rinsed and served.
    • Scenario 2: Toasting Gluten-Free Bread in an Uncleaned Shared Toaster Gluten-containing bread is toasted in a toaster. Immediately afterward, gluten-free bread is toasted in the same toaster.
    • Scenario 3: Slicing a Gluten-Free and Regular Cupcake with Same Knife

    The research team included Vanessa M. Weisbrod, BA; Jocelyn A. Silvester, MD PhD; Catherine Raber, MA; Joyana McMahon, MS; Shayna S. Coburn, PhD; and Benny Kerzner, MD. They are variously affiliated with the Celiac Disease Program, Children’s National Health System, Washington, DC, USA; and the Harvard Celiac Disease Program, Boston Children’s Hospital, Boston, MA.

    Their paper titled, Preparation of Gluten-Free Foods Alongside Gluten-Containing Food May Not Always Be as Risky for Celiac Patients as Diet Guides Suggest, appears in Gasterojournal.org.

    Control samples of gluten-free pasta, bread, and cupcakes all tested below the limit of detection. Samples were individually packaged in plastic bags with randomized sample numbers. To avoid “hot spots” and ensure even analysis, all items were homogenized for analysis. 

    Gluten content was measured with R5 sandwich ELISA (R7001, R-Biopharm, Darmstadt, Germany) which has a limit of detection of 5 ppm gluten by Bia Diagnostics (Colchester, Vermont). All control samples were similarly tested. 

    The team then quantified gluten samples as under 5ppm, 5-10ppm, 10-20ppm, or over 20ppm, and based their confidence intervals upon binomial distribution.

    Boiling Gluten-Free Pasta in Regular Pasta Water

    In the first scenario, the team boiled sixteen-ounce packages of gluten-containing Barilla brand penne and fusilli separately in stainless steel pots in fresh tap water for 12 minutes, then removed with strainers. The water was reused to cook Dr. Schar gluten-free penne and fusilli. The team also tested the effect of rinsing some samples of the cooked and contaminated pasta under cold tap water for 30 seconds. 

    The team found that Gluten was detected in all pasta samples cooked in water used for gluten-containing pasta, ranging from 33.9ppm to 115.7ppm. The rinsed gluten-free pasta samples tested at 5.1 ppm and 17.5 ppm detectable gluten. 

    Interestingly, rinsing pots with water alone after cooking gluten-containing pasta was as effective as scrubbing with soap and water to prevent detectable gluten transfer. 

    Toasting Gluten-Free Bread After Non-Gluten-Free Bread

    In the second scenario, the team toasted regular gluten-containing bread in two rolling toasters in a busy hospital cafeteria at 20-minute intervals, or in one of three shared pop-up toasters. Immediately after toasting the gluten-containing bread, they toasted Dr. Schar Artisan White Bread. Gluten-containing crumbs were visible in all toasters. They team did not clean the toasters. 

    The team found that toasting in a shared toaster was not associated with gluten transfer above 20ppm; the four samples with detectable gluten had levels ranging only from 5.1 ppm to 8.3 ppm gluten.

    Slicing a Gluten-Free Cupcake with Knife Used on Gluten Cupcake

    In the third scenario, the team used a knife to slice frosted gluten-containing cupcakes. The knife was then reused to slice a frosted gluten-free Vanilla Cupcake from Whole Foods Gluten-Free Bake House. 

    The knife was then washed in soap and water, rinsed in running water, or cleaned with an antibacterial hand wipe (Wet Ones) and a new gluten-free cupcake was sliced. Both gluten-free cupcakes were analyzed for gluten content.  Although 28/30 cupcake samples had detectable gluten transfer, only 2/28 tested over 20ppm. 

    The team found that cutting cupcakes with a knife used to cut frosted gluten-containing cupcakes was associated with low-level gluten transfer even when crumbs were visible on the icing adhered to the knife. All three knife washing methods tested were effective in removing gluten. 

    The team acknowledges the limitations of their study, including small sample size, etc. They are calling for further study to assess best kitchen practices for people with celiac disease who are trying to avoid gluten contamination in shared kitchens.

    Main Takeaways

    1) Some kitchen activities may pose less of a risk of cross-contact with gluten than is commonly believed. 
    2) Standard washing effectively removes gluten from shared utensils.
    3) Cooking gluten-free pasta in the same water as regular gluten-containing pasta is likely okay, as long as the pasta gets rinsed well.
    4) Sharing a toaster is unlikely to result in gluten contamination.

    Read more in Gastrojournal.org

    Conflict of Interest Declaration: JAS has served on an advisory board of Takeda Pharmaceuticals and received research support from Cour Pharma, Glutenostics, and the Celiac Disease Foundation. The other authors have no conflicts of interest to disclose. Funding Source: Supported by philanthropic gifts from the Celiac Disease Foundation, Dr. SCHAR USA, and Bia Diagnostics. JAS is supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number K23DK119584. 


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    On 10/21/2019 at 7:41 AM, Karen B. said:

    And for someone that reacts to gluten levels lower than 20 ppm?

    It took me awhile to believe my body was that sensitive but I have proved it to myself over and over. All this"study" accomplished is providing ammo to people to dismiss the concerns and requests of people with Celiac.   

    Yes, exactly! Seems irresponsible to spread this nonsense especially on this site of all places!

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    I don't think it's bad to perform studies like this, but I do think the results can be more harmful than helpful depending on who's lap the information falls in. This study is interesting, but is it useful or helpful to people cooking at home or at restaurants? In my opinion it is not. I think it could even give false hope to celiacs who might read it and think it's ok to trust a restaurant with food prep, or make people feel more relaxed about cross contamination. I don't know how most celiacs feel but the only thing that would make me feel more relaxed about cross contamination is if everyone was more well educated about gluten allergies and how they work.

    5ppm, 10ppm, 20 ppm, this is not basic knowledge for most people. It's not helpful to most people to talk about a food item being under 20ppm or not. What we really need to do is teach people how to properly clean. How to use their eyes to check a fork while it's being washed, to see if it has any food stuck to it. We need to teach people how to take their time and be meticulous about removing gluten from a countertop, dishes, or sponge. It just take a little work and a little effort. We need to teach restaurants and bars NOT to label menu items gluten-free if they don't have a dedicated prep area. They need to understand basic hand washing, outfit and apron changes, etc, how to be really careful if they are preparing both gluten-free and non gluten-free items. 

    Honestly for me it comes down to just use your eyeballs! If you see gluten, wipe it off. If you see crumbs on a plate and you're not sure what it is, scrape it off. There is no need for separate plates and utensils in your own home if stuff is cleaned properly. I do think in your own home if you have to be meticulous and careful every day, that is very stressful, so I think everyone needs to help out, or everyone needs to be ok with the household being mostly gluten free. Don't eat at restaurants unless you know the owner's level of knowledge (like they have celiacs or their wife has celiacs etc etc). 

    Cleanliness (to the extent celiacs need) and food prep dedication is really difficult and probably not cost effective for most restaurants. Not to mention, purchasing ingredients and understanding certifications and the ppm issues. This is just not feasible for most places. I don't expect this to change any time soon, and I don't think this study helps with these real life issues either. 

     

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    On 9/24/2019 at 7:22 AM, PhilSieg said:
    17 hours ago, Ali Rae said:

    I don't think it's bad to perform studies like this, but I do think the results can be more harmful than helpful depending on who's lap the information falls in. This study is interesting, but is it useful or helpful to people cooking at home or at restaurants? In my opinion it is not. I think it could even give false hope to celiacs who might read it and think it's ok to trust a restaurant with food prep, or make people feel more relaxed about cross contamination. I don't know how most celiacs feel but the only thing that would make me feel more relaxed about cross contamination is if everyone was more well educated about gluten allergies and how they work.

    5ppm, 10ppm, 20 ppm, this is not basic knowledge for most people. It's not helpful to most people to talk about a food item being under 20ppm or not. What we really need to do is teach people how to properly clean. How to use their eyes to check a fork while it's being washed, to see if it has any food stuck to it. We need to teach people how to take their time and be meticulous about removing gluten from a countertop, dishes, or sponge. It just take a little work and a little effort. We need to teach restaurants and bars NOT to label menu items gluten-free if they don't have a dedicated prep area. They need to understand basic hand washing, outfit and apron changes, etc, how to be really careful if they are preparing both gluten-free and non gluten-free items. 

    Honestly for me it comes down to just use your eyeballs! If you see gluten, wipe it off. If you see crumbs on a plate and you're not sure what it is, scrape it off. There is no need for separate plates and utensils in your own home if stuff is cleaned properly. I do think in your own home if you have to be meticulous and careful every day, that is very stressful, so I think everyone needs to help out, or everyone needs to be ok with the household being mostly gluten free. Don't eat at restaurants unless you know the owner's level of knowledge (like they have celiacs or their wife has celiacs etc etc). 

    Cleanliness (to the extent celiacs need) and food prep dedication is really difficult and probably not cost effective for most restaurants. Not to mention, purchasing ingredients and understanding certifications and the ppm issues. This is just not feasible for most places. I don't expect this to change any time soon, and I don't think this study helps with these real life issues either. 

     

     

    Best comment here yet!  (And also very diplomatic.) 

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    There is no way I could eat pasta that has been cooked in gluten contaminated water, use a toaster that is also used for gluten laden bread or use kitchen utensils used for glutened foods.  This is study is more for the gluten intolerant than the celiac.  I practically look at gluten and have an attack.  My kitchen will remain completely gluten free, thank you very much.

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    On 10/21/2019 at 5:02 PM, Jefferson Adams said:

    Actually, this study used rigorous scientific methodology, and makes its full results public without cost, unlike the site you mentioned. As for the takeaways, many folks have long believed they needed separate eating utensils because they thought that gluten would not rinse off, but this study clearly shows that gluten easily washes off flatware with standard washing methods.  Having a rigorous study actually quantify contamination levels for these scenarios is not only not flawed, it helps people actually quantify and understand actual risk levels. More and broader studies of this kind can help people move from fear and worry to actual knowledge and risk management. We welcome more of them.

    Here are comments from Dr. A. Fasano, (one of the world’s leading celiac disease researchers), about this study:

     

     

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    1 hour ago, kareng said:

    I guess my take away from all this is - sometimes using the same knife or oil or toaster doesn’t get gluten on the food ....... but sometimes it does.  And why would we relax our standards and hope we get lucky?   

    Those were my feelings exactly. I worry about what happens when studies like this are misinterpreted. I think they need to be followed up with how to apply what we've learned to everyday life safely and successfully. 

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  • About Me

    Jefferson Adams is Celiac.com's senior writer and Digital Content Director. He earned his B.A. and M.F.A. at Arizona State University, and has authored more than 2,000 articles on celiac disease. His coursework includes studies in science, scientific methodology, biology, anatomy, medicine, logic, and advanced research. He previously served as SF Health News Examiner for Examiner.com, and devised health and medical content for Sharecare.com. Jefferson has spoken about celiac disease to the media, including an appearance on the KQED radio show Forum, and is the editor of the book "Cereal Killers" by Scott Adams and Ron Hoggan, Ed.D.

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