Gliadin: What Is It, Where Can You Find It & Are You Allergic?
If you need to (or choose to) follow a gluten-free diet, you may not even be aware that a key player in your inflammation response to gluten is a small protein called gliadin. Knowing what it is can help you better understand your response to gluten—and how to avoid a serious reaction.
What is gliadin?
Gluten is composed of two main proteins—glutenin and gliadin. Gliadin makes up about 70% of the protein in gluten, and it's gliadin that causes the immune response for those who have celiac disease, as well as for many who don't have celiac but experience inflammatory symptoms after eating foods that contain gluten.
What is a gliadin allergy? How is it different from celiac?
A gliadin allergy occurs when the protein, gliadin, is not properly broken down (in a process called deamination), causing an immune response that results in inflammation and intolerance (and for many, various symptoms that may be similar to irritable bowel syndrome).
The difference between a gliadin allergy and celiac disease is that in celiac disease, people end up with damage to the lining of the intestine. On the other hand, in a gliadin allergy, there is no damage to the lining of the intestine. Additionally, people with gliadin allergies are not sensitive to glutenin, the other protein present in gluten (for reference, people with celiac disease are sensitive to gliadin and glutenin). However, it's impossible to remove just the gliadin from sources of gluten; so even if you just have an intolerance to gliadin, it's key to avoid gluten altogether in order to reduce symptoms.
Celiac and gliadin intolerance differ in terms of testing as well. Celiac is tested through a blood test, followed up by biopsy (the biopsy is usually the most helpful in diagnosing!). A non-celiac diagnosis, like gliadin intolerance or allergy, is generally guided by symptoms.
And you don't necessarily need to take a trip to the doctor's office—a registered dietitian can order a stool test and take a look at your anti-gliadin antibodies, which is local to the intestine sensitivity rather than systemically throughout your body as in the case of celiac. If these antibodies are high, it may indicate a sensitivity. The level of anti-gliadin antibodies can go down once you remove gluten from your diet and support the lining of your gut. (Another note: These anti-gliadin antibodies may also be elevated in someone with celiac).
For those with gliadin allergy, symptoms may include headaches, chronic urticaria, loss of menstruation in women, fatigue, stomachaches, or cramping. Bloating can also be part of the picture, as well as diarrhea.
The bottom line: Just because you don't have celiac disease doesn't mean you won't have trouble with gluten and the components it contains.
What foods is gliadin in?
Gliadin is primarily found in major sources of gluten—think bread, pasta, and pizza—but like gluten, it can also be found in other sneaky places like dressings, sauces, roux's, and in some cases of cross-contamination. In fact, a lot of people who are sensitive to gliadin find that it's the minor sources of exposure that cause the greatest problem. It makes sense—if someone is eating out at restaurants and being exposed to these sources frequently, it can cause persistent issues of intolerance, especially if someone's unaware of where it's coming from.
So, in order to avoid a possible gliadin allergy, you might want to examine smaller places you may be getting sneaky sources of gluten in your diet.
Major sources of gluten and gliadin.
Below are some of the more obvious sources of gluten and gliadin. These sources are pretty easy to spot, so it can be a little easier for the gluten and gliadin-intolerant to avoid. Again, it's impossible to remove just the gliadin from sources of gluten, so even if you don't necessarily have celiac, avoiding these gluten sources altogether is best.
- Wheat: Wheat is a major source of gliadin and is used in many places besides baked goods, breads, pastas, and pizzas—it's also used as a binder or filler in many processed foods.
- Barley: Barley contains gliadin and is used in many processed foods as a filler or sweetener (often found as barley malt in cereals).
- Rye: Rye contains gliadin, but it's fairly easy to avoid because it appears mostly in beer and rye bread, and it's not used in many manufactured foods (it usually appears on its own).
- Oats: If you have a gluten or gliadin intolerance, oats should be avoided unless they're marked gluten-free. Oats are naturally gluten-free, but gluten can appear as a result of wheat seed being spread into the oat fields or in cross-contamination during processing. So just do a double-check to make sure your oats are gluten-free.
Minor sources of gluten and gliadin.
People might not realize that these foods are the culprit for their inflammatory response. Here are some of the less obvious sources of gluten and gliadin.
- Dried fruits: It's the processing and cross-contamination that can create an issue for gluten intolerance, so always be sure to read your labels.
- Salad dressings: Thickeners for salad dressings often contain gluten—mainly barley and sometimes soy sauce.
- Brown rice syrup: Though brown rice is naturally gluten-free, the processing of the syrup can often involve barley enzymes.
- Miso: Sometimes the base of miso can also be made with barley, so you might want to double-check the miso paste you're using to make sure it's truly gluten-free.
- Pills and supplements: Gluten can be used to bind pills together, so find gluten-free substitutes if you can.
- Meat and poultry: The seasoning here may be the issue—sometimes hydrolyzed wheat protein and soy sauce in flavored, seasoned, or marinated meats are the culprits. Deli meats also often contain gluten.
- Soups, sauces, and gravies: Wheat flour is often used as a thickener for these types of items, so keep an eye on your labels!
Though gliadin allergies don't affect all of us, if you are someone who is sensitive to gluten—and you've been checked for celiac and the blood test is negative—you may have a gliadin allergy. If you feel uncomfortable from eating gluten, it can be helpful to avoid both major and minor sources of gliadin and be mindful of cross-contamination to see if it helps improve your symptoms.
People who avoid gluten tend to need to increase fiber in their diets, so look to add more vegetables and gluten-free whole grains (rice, buckwheat, amaranth, teff, quinoa) to your plate!
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Isabel Smith is a New York City-based dietitian, fitness expert, and founder of Isabel Smith Nutrition and Lifestyle. She received her B.A. in health and exercise sciences from Gettysburg College before a M.S. in nutrition communications at Tufts University. She also completed a dietetic internship and worked as an oncology fellow at New York Presbyterian Hospital. In her private practice, she works as a concierge nutritionist for both individual and corporate clients, including Fortune 500 corporations and their C-level executives. Smith has helped hundreds of people worldwide reach their nutrition, fitness, health, and wellness goals, and she also spends time writing and works as a nutrition consultant to a variety of health-minded brands.