What are the four types of gluten? An In-depth Nutritional Guide

October 8, 2025 •

4 min read

According to the Celiac Disease Foundation, gluten is a general name for proteins found in wheat, rye, and barley. Understanding what are the four types of gluten and their protein composition is crucial for managing gluten-related disorders such as celiac disease and non-celiac gluten sensitivity.

Quick Summary

This guide details the different protein families that are collectively referred to as gluten, found primarily in wheat, barley, and rye. It breaks down the specific components in each grain and explains how these different types can trigger various immune-mediated responses in sensitive individuals.

Key Points

Wheat contains two primary gluten protein families: Gliadin, which gives dough extensibility, and glutenin, which provides elasticity.
Barley's gluten protein is hordein, which is also a prolamin and triggers celiac disease symptoms.
Rye contains the protein family called secalin, which is similar to wheat gliadin and is toxic to those with celiac disease.
Oats have avenin, a distinct protein, which is not the same as gluten but can be cross-contaminated during processing.
Celiac disease is an autoimmune response to these gluten proteins, causing intestinal damage and requiring a lifelong gluten-free diet.
Non-celiac gluten sensitivity (NCGS) involves similar symptoms to celiac disease, but without the intestinal damage.

Demystifying the Four Main Gluten Protein Families

While the concept of four discrete types of gluten is a common simplification, gluten is more accurately described as a complex of different protein families found across specific cereal grains. The term "gluten" is often used to refer specifically to wheat, but similar protein families in barley and rye also trigger gluten-related disorders. The four protein families that most closely align with the idea of 'four types' are gliadin and glutenin in wheat, hordein in barley, and secalin in rye. These prolamins are resistant to complete digestion, and their unique molecular structures are responsible for triggering adverse reactions in genetically predisposed individuals.

Wheat: Gliadin and Glutenin

Wheat contains the two most well-known gluten protein families: gliadin and glutenin. These proteins are responsible for the unique viscoelastic properties of wheat dough, which allow it to be stretched and leavened for bread and other baked goods.

Gliadin: This is the monomeric, alcohol-soluble fraction of wheat gluten. Gliadin provides the dough with its viscosity and extensibility, making it soft and pliable. In individuals with celiac disease, certain gliadin peptide sequences are the primary trigger for the immune response. Gliadin itself is further classified into α/β, γ, and ω subtypes.
Glutenin: This is the polymeric, water-insoluble fraction of wheat gluten. Glutenin is a larger, more complex protein network that provides elasticity and strength to the dough. It consists of high-molecular-weight (HMW) and low-molecular-weight (LMW) subunits, all linked by disulfide bonds. Glutenin is what gives bread its chewiness and structure.

Barley: Hordein

Barley contains a protein family called hordein, which is structurally similar to wheat gliadin and also functions as a storage protein in the grain's endosperm. Hordein can trigger the same immune response seen in celiac disease, meaning barley and its derivatives must be strictly avoided by those with the condition. Hordein is also important in brewing and can contribute to the foaming and haze characteristics of beer.

Rye: Secalin

Rye's primary storage proteins are called secalins. Like gliadins and hordeins, secalins are prolamins that are high in glutamine and proline, making them difficult for the human digestive system to break down completely. These characteristics mean that secalins are also immunogenic for individuals with celiac disease and must be excluded from their diet. Triticale, a hybrid grain of wheat and rye, also contains gluten proteins.

Oats: A Special Case

While not containing a true gluten protein family, oats are often discussed in the context of gluten sensitivity. The protein in oats, avenin, has a different structure and is typically tolerated by most people with celiac disease. However, because oats are frequently processed in facilities that also handle wheat, barley, and rye, there is a high risk of cross-contamination. Therefore, individuals with celiac disease should only consume oats that are certified gluten-free.

Gluten-Related Disorders: Understanding the Reactions

For those with a gluten-related disorder, understanding the different proteins is key to managing health. The primary gluten-related conditions include:

Celiac Disease (CD): An autoimmune disorder where the immune system attacks and damages the lining of the small intestine in response to gluten consumption. It requires a strict, lifelong gluten-free diet.
Non-Celiac Gluten Sensitivity (NCGS): A condition causing gastrointestinal and other symptoms after gluten consumption, without the intestinal damage or antibody production characteristic of celiac disease.
Wheat Allergy: A classic food allergy where the immune system reacts to specific proteins in wheat (not just gluten), triggering a rapid, IgE-mediated response.
Gluten Ataxia: A neurological autoimmune disorder triggered by gluten, causing damage to the cerebellum and affecting coordination.

Practical Nutrition and Avoiding Gluten

For those who need to avoid gluten, meticulous label reading is essential. Gluten can be a hidden ingredient in many processed foods, serving as a binding agent or additive. Foods to be cautious of include sauces, dressings, soups, processed meats, and certain candies. When buying products, look for a "certified gluten-free" label to ensure safety from cross-contamination, especially with oats.

Comparing the Prolamin Families


Protein Family	Primary Grain Source	Protein Type	Key Characteristics	Impact on Health
Gliadin	Wheat	Monomeric	Viscosity, extensibility, makes dough soft	Primary trigger for celiac disease
Glutenin	Wheat	Polymeric	Elasticity, strength, makes dough firm	Contributes to the overall gluten complex that triggers autoimmune reactions
Hordein	Barley	Polymeric and Monomeric	Storage protein, structurally similar to gliadins	Triggers immune response in celiac disease
Secalin	Rye	Polymeric and Monomeric	Storage protein, rich in proline and glutamine	Triggers immune response in celiac disease
Avenin	Oats	Monomeric	Structurally different from other prolamins	Generally tolerated by most, but cross-contamination is a risk

Conclusion

In conclusion, the idea of what are the four types of gluten proteins can be clarified by understanding the specific protein families found in different grains. While wheat contains both gliadin and glutenin, barley and rye contain related prolamins called hordein and secalin, respectively. These proteins all have the potential to trigger adverse health reactions in sensitive individuals, including the autoimmune response of celiac disease. For managing a gluten-free diet, it is essential to be aware of the different sources and proteins involved. A healthcare professional can help properly diagnose and manage any gluten-related condition, ensuring a safe and nutritious diet. For further reading, an authoritative resource on celiac disease is available at the Celiac Disease Foundation.

Frequently Asked Questions

No, gliadin and glutenin are the two main protein families that make up gluten in wheat. However, other grains like barley and rye contain their own versions of these proteins called hordein and secalin, respectively, which can also trigger reactions in sensitive individuals.

Oats themselves contain a protein called avenin, which most people with celiac disease can tolerate. The main risk is cross-contamination from processing facilities that also handle wheat, barley, and rye. You should only consume oats that are specifically labeled or certified gluten-free.

Celiac disease is an autoimmune disorder that causes damage to the small intestine when gluten is consumed. Gluten intolerance, or non-celiac gluten sensitivity (NCGS), causes digestive symptoms but does not lead to the same intestinal damage as celiac disease.

Barley (hordein) and rye (secalin) contain prolamins that are structurally similar to wheat gliadins. These proteins are also rich in proline and glutamine, making them resistant to digestion and capable of triggering the same harmful immune response in those with celiac disease.

When wheat flour is mixed with water, gliadin and glutenin proteins combine. Gliadin provides dough with its viscous and extensible properties, while glutenin contributes elasticity and strength. This combination is essential for the structure of baked goods like bread.

The proteins collectively referred to as "gluten" are found in the endosperm of grains such as wheat, barley, rye, and triticale. The specific names vary depending on the grain, such as gliadin/glutenin in wheat, hordein in barley, and secalin in rye.

No, for the majority of the population, gluten is not inherently bad. For healthy individuals, gluten found in whole grains provides protein, fiber, and nutrients. Adverse reactions primarily affect people with diagnosed conditions like celiac disease or gluten sensitivity.