What Is Gluten?

Gluten is at the heart of celiac disease, yet despite the growing gluten-free diet fad, most people can’t properly answer the basic question, “What is gluten?” I’ll try to provide you a clear and useful definition and understanding. And to make sure you really understand gluten, this lesson ends with an interactive quiz.

Sadly, I’m confident most people would do poorly on this quiz without reading this lesson. Disagree? Go ahead and skip down and try the quiz before you read the lesson.

I’ve seen definitions from so-called authority sources defining this tricky protein mixture as a “sticky, elastic substance,” which is true to a degree but vague and not terribly helpful, a “protein,” which is not completely accurate as it is a protein composite, not a protein itself, and a “3-dimensional network formed from sulfur cross-linkage among proteins,” which is only accurate when kneading gluten-containing dough and not a very useful description for most casual researchers.

My goal is for you to be able to leave this lesson with not only a clear definition of gluten, but also with a comprehensive source you can share with friends and family and refer back to when you address different issues relating to this unique protein composite, whether from a cooking perspective (in baking or gluten-free baking) or from a health perspective (in celiac disease or a non-celiac gluten sensitivity).

Table of Contents:

What Is Gluten?

In the simplest terms, gluten is a protein composite, meaning it is a substance made up of several different proteins. It is found in wheat and related grains in the triticeae family of grassy grains or cereal grains. These grains include barley, bulgur wheat, durum, einkorn, farro, graham, kamut, rye, semolina, spelt, triticale and wheat.

Gluten's Origin

Gluten's Origin

Gluten comes from the endosperm within the seeds of these cereal grains (the adjacent picture shows an example of a wheat seed endosperm). This makes gluten proteins plant storage proteins. Storage proteins essentially feed embryonic plants during germination, a process common among the seeds in most flowering plants.

The proteins in gluten are unique storage proteins, however, in that they are also functional proteins. This unique functionality makes wheat difficult to substitute when creating gluten-free baked goods, as I describe in the next section on this odd protein’s most common uses.

The four primary protein types in gluten are albumins, globulins, glutelins and prolamins. In wheat gluten, glutelins and prolamins are far more prevalent than albumins and globulins. Albumins and globulins are the primary storage proteins in corn gluten and rice gluten and are not associated with celiac disease. Some take issue with the food industry for even using the term “gluten” in the context of corn or rice.

The specific proteins we are most interested in are the prolamin gliadin and the prolamin-like glutelin glutenin. They make up about 80 percent of the protein in wheat. These are the proteins which give this unique protein composite its distinct structure and function… and these are the proteins responsible for triggering celiac disease.

The cross-linking of gliadin molecules and glutenin molecules creates the primary properties we associate with gluten.

Prolamins are insoluble in water and are a general family of proteins common among these grassy grains. In fact, all the grassy grains related to wheat contain different prolamins, but since the polypeptide chains (sometimes just referred to as peptides) of each of these proteins is so similar to the proteins in wheat, they are still broadly called gluten. For example, while gliadin is the prolamin in wheat, secalin is the prolamin in rye and hordein is the prolamin in barley. These are also known as glycoproteins.

Glutelins are another prolamin-like family of proteins. The glutenin in gluten is a glutelin. Glutelins are heat-labile proteins, which means they are altered by heat (which is important for appreciating how gluten responds to baking), and are insoluble in water but soluble in dilute acids or alkalies (bases). While researchers consider the gliadins the more damaging proteins for people with celiac disease, the glutenins have also been shown to trigger a damaging autoimmune response in people with a genetic susceptibility to this pesky protein composite.

As I mentioned earlier, gluten also contains proteins called albumins and globulins, which are soluble in water or diluted salt water unlike the gliadins and glutenins. These are common storage proteins in many grains and do not greatly contribute to the unique quality of gluten-containing cereal grains. They are not known to trigger the problems triggered by glutenins and especially gliadins. When you see websites define gluten, they often don’t mention albumins and globulins because they are far less significant than glutenins and gliadins when discussing celiac disease.

Small side note: I’ve had a number of people write me asking, what is gluton? This is a common misspelling. The correct spelling is g-l-u-t-E-n, not gluton. Unlike with celiac and coeliac (which are both correct in different parts of the world), gluton is just a misspelling.

Back to Top

What Are Its Uses?

Because of the cross-linking of gliadins and glutenins, which occurs when you mix a gluten-containing grain with water, gluten provides the chewiness you’ve come to know in baked goods. Baked goods with a higher density of this unique substance feature greater chewiness (as is the case with bagels and pizza crust). Without gluten, common baked goods would be more sticky and less chewy.

Gluten also traps carbon dioxide produced during dough fermentation before baking, helping dough rise before it is baked. Additionally, it traps gases during the baking process, helping baked goods rise even more while baked. This capacity to trap gas also helps provide the light, flaky quality of some baked goods.

When dough is baked, gluten coagulates to help that bread, muffin or cake retain its shape. This is why early attempts at gluten-free bread and gluten-free baking in general tend to result in baked goods that crumble or collapse more compared to gluten-containing baked goods.

Heavier, chewier baked products feature higher concentrations of gluten while lighter pastry products feature a lower concentration. People in the flour industry measure the density and elasticity of gluten within flours using a Farinograph. This measurement helps determine the best cooking or baking role for a particular flour.

The food industry uses gluten, and wheat gluten in particular, in many ways because it is so easy and inexpensive to isolate gluten from starches. As it is a concentrated protein source and an absorbent substance, it is often used as a food additive, a protein supplement or even as a food by itself. Meat substitutes, also known as imitation meat or wheat meat, are often composed of concentrated gluten. For example, seitan, a popular asian food and meat substitute, is mostly just concentrated wheat gluten.

Perhaps most insidiously, gluten’s capacity to bind and provide thickness makes it common in flavorings and sauces. This is why gluten exists in many more food products than just the obvious baked products and why it is more pervasive in the western diet than most people realize.

Wheat starches are used in many products, partially because they are a cheap by-product of vital gluten manufacturing. Because these proteins can’t be completely removed from the wheat starch, products made with any amount of wheat starch are still dangerous for people with celiac disease.

Back to Top

How Is Gluten Extracted From Wheat?

Because it is insoluble in water, gluten is easily isolated by kneading whole wheat flour and rinsing it with water. If you knead wheat flour rigorously while slowly rinsing it with water, you will eventually have what looks and feels like an elastic rubber ball.

Wheat Flour Kneaded Into Gluten

The above image is how gluten looks when isolated from about a cup of wheat flour by kneading it under a standard kitchen faucet for five minutes.

IMPORTANT: It is not possible to completely remove all gluten proteins from a wheat starch. While various forms of the process I just described will separate the starches from a wheat flour, significant traces of gluten and its various composite proteins will remain in the starches. This is why if you are on a gluten-free diet you absolutely must avoid any product containing even a trace of wheat, wheat starch or starch from one of the cereal grains in the triticeae tribe.

Mass producing gluten involves using heavy machinery to knead a slurry of whole wheat flour — wheat flours mixed with cold water or saline solution — so the gluten isolates and collects into a distinct gluten mass. A centrifuge collects that mass and passes it to machinery to remove moisture.

First a screw press is used to remove most of the water, then the gluten passes into an evaporation chamber, where the temperature is raised just enough to dry the gluten mass without altering it.

At this point the gluten resembles a flour with minimal moisture. Finally the gluten flour is milled and sifted into the density and evenness required for the intended end product. When you see vital wheat gluten sold in stores or listed as an ingredient, it probably came from this isolation process.

Back to Top

What Is Gluten Intolerance?

The term gluten intolerance is really an umbrella term, and underneath that umbrella we have three fundamentally different conditions. The two primary forms of gluten intolerance are celiac disease and a non-celiac gluten sensitivity. Additionally, some people can suffer from a wheat allergy, which is quite different from celiac disease or non-celiac gluten sensitivity, but since it is a food allergy involving wheat you will often see people discuss it as a form of gluten intolerance.

When most people use the term gluten intolerance, however, they are likely referring to celiac disease.

Only in the spring of 2011 did doctors and researchers verify and isolate the existence of a non-celiac gluten sensitivity. Unfortunately, because a separate and distinct form of gluten sensitivity has only recently been isolated and defined, diagnosis can be difficult. At this point, the most likely scenario for being diagnosed with a gluten sensitivity is simply testing negative for both celiac disease and a wheat allergy yet still exhibiting clear signs of a poor response to consuming gluten. Currently doctors and researchers are trying to develop more clear and useful biomarkers for diagnosing this non-celiac sensitivity.

When taken all together, these different forms of gluten intolerance indicate some startling gluten intolerance statistics.

Back to Top

Gluten-Sensitive Enteropathy

Gluten Enteropathy, or gluten-sensitive enteropathy, is simply another name for celiac disease, which you will also find called celiac sprue disease, non-tropical sprue or endemic sprue. In different parts of the world celiac is spelled coeliac, which just furthers the confusion.

Celiac disease is an autoimmune disease that manifests itself primarily in the small intestine. It occurs in people who inherit one or both of the celiac genes, which are HLA-DQ2 and HLA-DQ8.

When people with celiac disease consume gluten, the enzyme tissue transglutaminase alters the gliadin in the gluten, which causes an immune system reaction that damages the lining of the small intestine. This is why celiac disease is called an autoimmune disease: the immune system attacks its own body.

This reaction causes inflammation and damages the villi and microvilli along the walls of the small intestine (a phenomenon labeled villous atrophy). These microvilli are tiny hair-like fingers that reach out from our small intestine walls to grab nutrients from food passing through our bowel. When the villi are truncated, we are less able to absorb nutrients from our food.

The damage gluten inflicts on intestinal villi

In addition, this damage creates a phenomenon called intestinal hyperpermeability, more often simply referred to as leaky gut syndrome. When you suffer from leaky gut syndrome, both protein fragments and toxins that should have remained in your small intestine pass through your intestinal wall into your bloodstream.

It is the combination of these two phenomena — villous atrophy and intestinal hyperpermeability — that cause the broad range of possible celiac disease symptoms.

We don’t know what triggers people to become celiacs. That might sound odd as you might assume that gluten triggers people to develop celiac disease. But suffering from the reaction to gluten is the disease; what we don’t know is what causes somebody who is genetically predisposed to finally develop the disease.

Some people who are genetically susceptible may go most of their lives without developing celiac disease or suffering from a poor response to consuming gluten. Something takes us from susceptibility to manifestation, and scientists still haven’t identified that exact trigger.

Back to Top

Gluten Withdrawal

What is gluten withdrawal? When people eat foods containing this complex protein composite, it triggers the body to manufacture exorphins, which are opioid chemicals similar to endorphins. This produces a calm, relaxed feeling. And just as opiates cause withdrawal when opiate consumption is stopped, you can experience a degree of withdrawal when you completely remove gluten from your diet.

To make things worse, people who need to go gluten-free often need to go dairy-free or casein-free as well, and casein, the primary protein in cow’s milk, also triggers the body to manufacture exorphins.

This withdrawal can cause irritability and intense cravings you don’t expect or understand.

Additionally, as your body heals during the first week or so of going gluten-free, you may experience some mild rashes, hives and headaches. This is because your body, and in particular your liver, can suddenly better process and eliminate toxins. When you go through this kind of detox period you may experience some temporary symptoms or side-effects resulting from your body working through and eliminating these toxins.

Back to Top

Gluten-Free Diet

Of course the simple definition is that a gluten-free diet is a diet that strictly excludes gluten. To understand what that means you not only need to understand gluten and gluten intolerance, but you also have to understand how manufacturers and researchers define the term gluten-free.

Simply put, you’ll discover some confusing and controversial elements to the term gluten-free and what has been defined as acceptable on a gluten-free diet.

First, when you see something labeled as gluten-free, that means that it contains less gluten than the minimum standard considered to be harmful. Unfortunately, that minimum standard varies all over the world and is a bit controversial.

The FDA set guidelines to define a gluten-free food as a food containing less than 20 ppm (parts per million) gluten, or a food with 0.002% of this sticky, troublesome substance. This is the same as the international Codex Alimentarius standard. But in Australia they have determined that a food must contain 5 ppm gluten (0.0005%) to be considered gluten-free.

Some recent research suggests it may take even less gluten per day than we once thought to cause damage to our intestines. Read more about this in this other lesson: How Much Gluten Is Too Much?

Be Healthy

When you embark on a gluten-free lifestyle, you must make certain you obtain enough fiber, folate, iron, niacin, riboflavin, selenium and thiamine. These are nutrients often lacking in a gluten-free diet because they are often fulfilled by gluten-containing foods on a standard diet. In addition, you need to be careful you don’t fill your diet with too many simple carbohydrates.

When you go gluten-free, you still need to try to eat gluten-free whole grains and gluten-free nuts. Too many refined flours like white rice flour will not provide you a healthy way forward. Replacing relatively healthful gluten-containing grains with too many simple carbs often leads to the phenomenon of gluten intolerance and weight gain.

My Gluten Free Pantry may be a good starting point for people learning how to replace gluten in their everyday baking.

Because you may need to avoid lactose or casein as well, at least when you first start your recovery, you may have to avoid dairy products. So calcium and protein will also need to be monitored and you may need to be deliberate in how you replace these nutrients.

Back to Top

What Foods Contain Gluten?

This is the most intimidating and frustrating part of asking, what is gluten? I’ll provide you an outline and foundation for all the foods containing gluten, but I’m afraid you’ll need to flesh this list out with some of your own research as needed. A single static and complete list just isn’t possible as brands, recipes and formulas are constantly changing. Please always check the label and never assume anything.

When in doubt, contact the manufacturer. And because the person answering the phone or your email may not always fully understand gluten, be prepared to ask if any of the terms, products or ingredients mentioned below are in the products (such as wheat starch, hydrolyzed protein, or even non-wheat gluten products, such as barley or rye).

Recent gluten-free labeling guidelines released by the FDA in the United States should make this process a little easier eventually, but it will take some time for them to be useful for the average consumer.


Most Common and Potent Source of Gluten: Wheat

First, we start with any food made from — or supplemented with — one of the cereal grains in the Triticeae tribe:

  • Barley
  • Bulgur wheat
  • Durum
  • Einkorn
  • Farro
  • Graham
  • Kamut
  • Rye
  • Semolina
  • Spelt
  • Triticale
  • Wheat

The most important here are wheat, barley and rye, especially wheat and barley. Each of these make it into foods as hidden sources of gluten because different parts of them are used as flavor enhancers, binders, thickeners, protein enhancers and more.

Wheat starch — which despite being separated from gluten still contains significant and harmful traces of its proteins — must be avoided and you will often find it used in sauces like soy sauce, barbecue sauce or hydrolyzed flavor enhancers. Malted barley also makes it into a ton of foods as a primary ingredient (like in beer, which is why it can be hard to find good gluten free beer) or as a flavor enhancer (like in malted milk). Any product suggesting a wheat germ was used in it will also contain gluten.

The following is a strong foundation list of foods containing gluten, but please understand a comprehensive list would be far larger. I still hope it is enough to give you a more clear and helpful picture of what you must avoid.

This list includes foods that can and often do contain gluten, but in some cases you can find variations of them that are gluten-free. In some cases, an item on the list may be fine, but I put it on this list to alarm you to a food you may need to further research.

  • Bouillon
  • Bran
  • Breakfast Cereals
  • Broth (Chicken Broth, Beef Stock and Vegetable Stock, including Stock Cubes)
  • Burgers
  • Canned And Prepared Soups
  • Cooking Wines
  • Couscous
  • Cured Meats
  • Dextrin
  • Flavored And Herb Cheeses
  • Flavored Coffees
  • Flavored Dairy Products, Like Yogurt And Pudding
  • Flavored Liqueurs And Liquors
  • Flavored Vinegars
  • Gravy
  • Herbal Teas (Barley is sometimes added)
  • Hot Dogs
  • Imitation Meats or Meat Substitutes (even when they’re Soy-Based)
  • Instant Coffee, especially Flavored Instant Coffee
  • Jerky
  • Ketchup (or “Catsup”)
  • Marinades
  • Matzo
  • Orzo
  • Pickles
  • Roasted Or Flavored Nuts
  • Salad Dressings
  • Sauces
  • Sausage
  • Seitan
  • Self-Basting Poultry
  • Soy Sauce
  • Spice Blends (including Curry Powders)
  • Tamari
  • Veggie Burgers
  • Veggie Dogs
  • Veggie Sausages

And while the following should be obvious, you can never be too safe:

  • Bagels
  • Biscuits
  • Bread
  • Cakes
  • Croissants
  • Muffins
  • Pancakes
  • Pasta
  • Pastries
  • Pie Crusts
  • Pizza Crusts
  • Pretzels

Because it can be used as a stabilizing agent and thickener, the number of subtle, hidden sources of gluten can be alarming. For example, some manufacturers use it in the sticky stuff you use to seal envelopes!

One last area: oats. I’m developing an entire guide to gluten in oats because it has become so confusing and controversial. The bottom line is that oats by themselves are technically gluten-free, but in most cases they are not safe for people on a gluten-free diet because of cross contamination. Oats are so often grown and processed alongside gluten-containing grains that they are almost always cross-contaminated.

To makes things even more difficult, just because an oat product is certified gluten-free doesn’t mean you should splurge. A small percentage of people who are sensitive to this pesky protein composite are also sensitive to the storage proteins in oats, so even if you want to start eating certified gluten-free oats, you should only do so slowly and with your physician’s supervision.

You will need to be diligent about reading labels and you will need to grow accustomed to regularly contacting manufacturers.

Back to Top

Gluten-Free Foods

While a complete list of gluten-free foods would take pages and pages to convey, the following list should cover the most frequently desired gluten alternatives for cooking and baking.

It should also illuminate some food opportunities you hadn’t previously considered.

First, let’s start with some common pre-made ingredients.

  • Brown and white rice pasta
  • Brown rice tortilla wraps, when made from 100% brown rice flour
  • Corn pasta, when made from 100% corn
  • Corn tortillas and corn taco shells, when made from 100% corn
  • Nut butters (check the label, but you should be fine in most cases): this includes almond, cashew and peanut butters.
  • Polenta rolls, but always check for the gluten-free label
  • Quinoa pasta and some quinoa pasta combinations (look for gluten-free label)
  • Rice noodles and rice glass noodles
  • Rice paper or rice and tapioca paper wraps
  • Seed butters: This includes hemp seed butter, sesame tahini, sunflower seed butter.
  • Soba noodles (make sure they are 100% buckwheat)
  • Soy pasta (if labeled gluten-free)
  • Teff wraps created with 100% teff flour

Remember to always look for a gluten-free label, and in the case of products made with a specific gluten-free flour, make sure it is made from 100% of that flour.

Now let’s consider common alternatives.

When you consider wheat flour replacements, you will find a number of plants, nuts and grains used in combinations (you can view some of my suggested combinations in my gluten free pantry). This list includes flours, starches and thickeners. There is no one-for-one replacement for wheat flour, and most recipes will include two or more of the following in combination:

  • Amaranth flour
  • Arrowroot starch
  • Buckwheat (includes Kasha)
  • Chick pea or garbanzo flour
  • Coconut flour
  • Corn (including cornmeal, corn starch and masa harina)
  • Millet flour
  • Nut meals and flours, including almond, cashew, chestnut, pecan and walnut (almond flour is a favorite of mine)
  • Potato flour (as a thickener)
  • Potato starch (for baking)
  • Quinoa flour
  • Rice flour (includes white rice, sweet rice and brown rice flours)
  • Sorghum flour
  • Soy flour
  • Tapioca starch, also called tapioca flour
  • Teff flour

I should make a special mention about oats. For most celiacs, certified gluten-free oats and oatmeal made with these carefully grown and packaged oats will be okay.

The conventional wisdom of avoiding oats on a GF diet has more to do with cross-contamination with gluten-containing grains during processing. However, if you have not been eating oats, I recommend you only begin eating them under the supervision of your doctor.

In some patients the protein in oats appears to cause a similar reaction to the reaction caused by consuming gluten. This is rare, so please don’t panic, but it is possible. In most cases, when oats are certified gluten-free, they should be fine for people with an intolerance or sensitivity.

Back to Top

And that ends my comprehensive guide to What Is Gluten? I don’t expect you to read this entire guide in one session, but I hope you will bookmark it and refer to it as you need.

It is a strange phenomenon, but you would be surprised how many people living a gluten-free lifestyle can’t really define gluten. If you’ve followed along here, now you will be one of the few people who really can.

Take The Quiz!

How Well Do You Understand Gluten?

This short quiz will help you master your understanding of gluten. It's a topic surrounded by hype and many in the media parrot myths and misunderstandings. If your health is at stake, you need to be certain you really understand gluten.

If you select the wrong answer, you may try to select another answer before moving to the next question. An explanation for each question is provided either when you select the right answer or at the end of the quiz.


Congratulations - you have completed How Well Do You Understand Gluten?.

You scored %%SCORE%% out of %%TOTAL%%.

Your performance has been rated as %%RATING%%

Your answers are highlighted below.
Shaded items are complete.