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What is gluten?

Common foods, conditions, symptoms, and more

Gluten is a protein found in many foods. This article explores who should avoid gluten, what foods contain it, how to eat a gluten-free diet, symptoms, and more.

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This article is based on scientific evidence, written by experts, and fact-checked by experts.
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Last updated on September 22, 2022, and last reviewed by an expert on July 14, 2022.

Gluten-free diets have become increasingly popular in recent years, especially due to the growing awareness of gluten-related disorders.

In turn, this has fueled a rapid rise in the mainstream availability of gluten-free food options. The gluten-free food industry was valued at $4.3 billion in 2019.

The introduction — and increase in availability — of these products made what was once a difficult-to-stick-to diet much easier to follow.

Although gluten-free diets are more common, gluten does not pose a health risk to the majority of the U.S. population, as less than 1% of it is affected by celiac disease.

That said, people with celiac disease, non-celiac gluten sensitivity, and some other conditions must eliminate gluten from their diets to avoid harmful, adverse reactions.

This article reviews everything you need to know about gluten, including what it is, which foods contain it, who may need to follow a gluten-free diet, and how to eat a gluten-free diet.

What is gluten?

Gluten is a family of storage proteins — formally known as prolamins — that are naturally found in certain grains, such as wheat, barley, and rye.

Many prolamins fall under the gluten umbrella, but they’re most commonly identified by the specific grains in which they’re found. For instance, glutenins and gliadins are the prolamins in wheat, secalins are found in rye, and hordeins are found in barley.

In foods, gluten has a variety of functional culinary benefits. It gives many grain-based foods their soft chewy texture.

In bread, for instance, gluten proteins form an elastic network that stretches and traps gas, allowing the bread to rise and retain moisture.

Because of these unique physical properties, gluten is also frequently added to processed foods to improve texture and promote moisture retention.

Summary: Gluten is a group of various proteins found in certain grains. It performs a variety of beneficial functions in bread products, but those with celiac disease cannot tolerate it.

Foods that contain gluten

Gluten may be found in a variety of whole and processed foods, including:

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Suggested read: Gluten-free foods list: 54 foods you can eat

Because gluten is often used in food production as a thickener or stabilizer, it’s not always clear whether a particular food contains it.

What’s more, many commercial food operations share preparation equipment with gluten-containing foods. Thus, even if a food is inherently gluten-free, it could be contaminated with gluten during processing.

If you follow a strict gluten-free diet and are unsure about a particular food’s gluten status, check the package for a gluten-free label or contact the manufacturer before purchasing it.

Oats

When it comes to gluten-free diets, oats are a bit of a conundrum.

One of the main issues with oats is that they’re frequently transported and processed with equipment that’s also used to process wheat. This leads to the widespread gluten contamination of oats, even if there isn’t mention of wheat or gluten on the product label.

Suggested read: Gluten foods list: List of what to avoid and alternatives

Still, it’s easy to find oats that are certified and labeled gluten-free. Gluten-free oats are simply regular oats that have been processed using equipment and facilities that are free of gluten contamination.

However, some experts argue that there’s no such thing as gluten-free oats — even if they’re labeled as such.

That’s because oats contain a protein called avenin, whose structure is very similar to those of the proteins in gluten.

Early research suggests that, in rare cases, a small percentage of people with gluten-related disorders may react similarly to avenin as they do to gluten.

That said, the vast majority of current evidence suggests that most people with gluten-related disorders can tolerate gluten-free oats without issues.

Uncontaminated oats are often encouraged for gluten-free diets due to their rich supply of fiber and essential nutrients.

Ultimately, more research is needed to better understand how the avenin in oats affects digestion and immune function in people with gluten-related disorders.

If you suspect that you may be intolerant to oats, talk with your healthcare professional.

Summary: Gluten may be present in a variety of foods, including wheat, barley, rye, and related grains. It’s also used as a thickening agent in processed foods. Look for gluten-free oats to be sure they haven’t been processed in a facility with gluten.

What does a gluten-free label mean?

If you’re working on eliminating gluten from your diet, it can be challenging to know whether a product was supplemented with a gluten-containing ingredient or inadvertently contaminated during processing.

This is why many government health authorities have implemented gluten-free food labeling regulations.

While these labels can make gluten elimination much easier, they don’t necessarily mean that gluten is completely absent from the item.

In the United States, the European Union, and Canada, a product can carry a gluten-free label as long as gluten makes up fewer than 20 parts per million (ppm) of the product. That means that for every million parts of the food, up to 20 of them can be gluten.

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The 20 ppm threshold was set due to some evidence that suggested that the majority of people with gluten-related disorders are unlikely to experience adverse reactions at this level. However, some countries have opted to set the limit as low as 3 ppm.

Summary: Gluten-free food labels are used in many countries, but they don’t mean that a particular product is completely free of this protein. Most countries allow up to 20 ppm of gluten in products labeled gluten-free.

Certain medical conditions may require a gluten-free diet

Though gluten is safe for most people, certain medical conditions require a gluten-free diet as part of the treatment protocol.

Celiac disease

Celiac disease is a serious autoimmune condition in which a person’s immune system attacks cells of their small intestine when they ingest gluten.

It’s one of the most well-researched causes of gluten intolerance and is estimated to affect approximately 1% of the global population.

Like many other autoimmune conditions, the exact cause of the celiac disease remains unclear, but there is strong evidence of a genetic component.

Medicinal treatments for celiac disease are currently being researched, but the most widely accepted and utilized treatment is a strict gluten-free diet.

Non-celiac gluten sensitivity

Non-celiac gluten sensitivity (NCGS) describes several negative symptoms that are resolved when gluten is eliminated from the diets of people who do not test positive for celiac disease or wheat allergy.

At this point, very little is known about NCGS, but current treatment includes adherence to a gluten-free diet.

Irritable bowel syndrome

There’s a bit of an overlap between NCGS and irritable bowel syndrome (IBS), as some people who suffer from IBS report wheat as food they can’t tolerate.

Within the scientific community, it’s unclear why wheat can be problematic for some people with IBS but not others.

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Either way, some research suggests that a gluten-free diet may be appropriate for some people with IBS, and especially for those with IBS-D, or irritable bowel syndrome-diarrhea.

Wheat allergy

A wheat allergy is not a gluten-related disorder, but it’s a closely related condition.

Wheat allergies are an intolerance to wheat itself, not just the gluten protein. Thus, someone with a wheat allergy must avoid wheat but may still safely consume gluten from nonwheat sources like barley or rye.

That said, many people who have a wheat allergy end up following a mostly gluten-free diet because the two ingredients are so closely linked and coexist in many of the same foods.

Children with a wheat allergy often outgrow it and can incorporate wheat into their diet around school age.

Summary: Certain medical conditions require a gluten-free diet as a treatment. These include celiac disease, non-celiac gluten sensitivity, and gluten-related disorders like wheat allergies.

Common symptoms of gluten intolerance

Symptoms of gluten intolerance can manifest very differently depending on the individual.

The range of possible symptoms that may be caused by gluten-related disorders is vast and not always intuitive. Some people have no obvious symptoms at all, and conditions like celiac disease or NCGS often go untreated or misdiagnosed.

Symptoms of gluten-related disorders may include:

If you suspect that you have a gluten-related disorder, you should consult a healthcare professional — even before attempting to eliminate gluten from your diet.

Suggested read: The gluten-free diet: A beginner's guide with meal plan

Some testing procedures for certain gluten-related conditions like celiac disease may give inaccurate results if you’re already adhering to a strict gluten-free diet.

What’s more, certain symptoms that may seem like a reaction to gluten could be a reaction to something else.

Thus, the best first-line approach is to discuss your symptoms with a healthcare professional before attempting to diagnose or treat yourself.

Summary: Gluten-related disorders can cause a very broad range of symptoms, including digestive problems, skin rashes, weight loss, headaches, and bone loss.

What to eat on a gluten-free diet

A large number of foods are naturally gluten-free, such as fresh fruits and vegetables, most unprocessed or fresh animal meats and seafood, many fats and oils, and more.

Here is some guidance on what you can eat within each of the main food groups if you have a gluten-related disorder.

Fruits and vegetables

All fresh fruits and vegetables are gluten-free. However, gluten-containing ingredients are sometimes added to processed fruits and vegetables, particularly if they’re flavored.

Produce that’s plain and frozen, canned in just water or juice, or unsweetened and dried are typically gluten-free, too, but check labels just to be sure.

Proteins

Most fresh, plain, and unflavored proteins are naturally gluten-free. For instance, red meat like fresh beef, pork, lamb, and bison; fresh chicken, turkey, and seafood; nuts and seeds; legumes; and traditional soy foods, such as tofu, tempeh, and edamame.

Breaded proteins should be avoided. Check any proteins that are processed (e.g., hot dogs, deli meats, etc.) or combined with any sauces or seasonings, as well as ground meats.

Dairy products

Many dairy products, particularly those that are plain or unflavored and/or don’t contain additives, are inherently gluten-free.

Suggested read: Healthy vegan foods

Be sure to check flavored milk and yogurts, processed cheese products — especially spreads and sauces and ice cream to ensure the one you’re purchasing is gluten-free.

Fats and oils

Nearly all fats and oils, from butter and ghee to oils made from nuts and seeds, are naturally gluten-free. Double-check all cooking sprays, though, as well as any flavored or spiced oils.

Summary: Most fresh, whole, and unprocessed fruits, vegetables, protein-based foods, fats, and oils are naturally gluten-free. When those food items are processed or flavored or even just packaged, check the ingredient list or look for a gluten-free label.

Summary

Gluten-free diets are more popular than ever, but there’s often confusion about what gluten is and when it ought to be eliminated.

Gluten refers to a variety of proteins naturally found in cereal grains, such as wheat, barley, and rye.

There’s nothing inherently unhealthy about gluten, but people with certain medical conditions like celiac disease, non-celiac gluten sensitivity, or wheat allergy should avoid it, as it may cause serious adverse reactions.

Symptoms of gluten-related disorders are broad and may include digestive issues, inflamed skin, and neurological problems.

If you suspect that you have a gluten-related disorder, consult a qualified healthcare professional.

Try this today:

It can be easy to rely on gluten-free versions of your favorite snacks — think cookies, crackers, pretzels — but many naturally gluten-free grains will give you a nutrient boost. Enjoy rice, quinoa, corn, and more.

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