what is gluten

Gluten seems to be in just about everything, from bread, pasta and beer to cosmetics and nutritional supplements. There’s lots of buzz around avoiding gluten, but what is this common ingredient and is it really bad for you? Johns Hopkins specialist in internal medicine and obesity Selvi Rajagopal, M.D., explains facts and misconceptions about gluten.

What is gluten?

“Gluten is a protein found in the wheat plant and some other grains,” explains Rajagopal.

Gluten is naturally occurring, but it can be extracted, concentrated and added to food and other products to add protein, texture and flavor. It also works as a binding agent to hold processed foods together and give them shape.

Where does gluten come from?

In addition to wheat, gluten also comes from rye, barley and triticale (a cross between rye and barley). Sometimes it’s in oats, but only because the oats may have been processed with other foods that contain gluten. Oats themselves don’t contain gluten.

What does gluten do to your body?

Humans have digestive enzymes that help us break down food. Protease is the enzyme that helps our body process proteins, but it can’t completely break down gluten. Undigested gluten makes its way to the small intestine. Most people can handle the undigested gluten with no problems. But in some people, gluten can trigger a severe autoimmune response or other unpleasant symptoms.

An autoimmune response to gluten is called celiac disease. Celiac can damage the small intestine. Some people who don’t have celiac disease still seem to feel sick after eating foods that contain gluten. They may experience bloating, diarrhea, headaches or skin rashes. This could be a reaction to poorly digested carbohydrates, not just gluten. These carbs, called FODMAPS, ferment in your gut. People with sensitive guts may experience discomfort from that fermentation, not necessarily from gluten.

Research suggests that some people could have small intestines that don’t work properly. The lining might be too permeable, allowing some undigested gluten, bacteria or other substances to go through the lining and into the bloodstream, causing inflammation.

Is gluten bad for you?

“There’s a lot of confusion about gluten being an evil food. Gluten isn’t inherently bad for most people,” says Rajagopal. “We, as humans, have consumed gluten for as long as people have been making bread. For centuries, foods with gluten have been providing people with protein, soluble fiber and nutrients.”

Gluten in itself, especially gluten found in whole grains, is not bad for healthy people whose bodies can tolerate it. However, grains like wheat are often stripped down to make processed foods such as snack crackers and potato chips. “These refined products have very little resemblance to the actual wheat plant, which is actually highly nutritious,” explains Rajagopal. “They tend to contain things like white rice flour and starches, but not whole grains.”

Many people who adopt a gluten-free diet but still eat processed foods find they continue to have weight gain, blood sugar swings and other health issues. So it’s not the gluten in foods that’s causing their health issues, but the sodium, sugar and other additives in processed foods.

Who should avoid gluten?

Rajagopal says gluten can be harmful to people with:

  • Celiac disease, an autoimmune disease that causes damage to the small intestine in people who consume gluten.
  • Non-celiac gluten sensitivity (gluten intolerance), which is gastrointestinal irritation caused by gluten in people who don’t have celiac disease.
  • Wheat allergy, an allergy to wheat, but not to all grains or to gluten itself.
  • Gluten ataxia, a rare neurological autoimmune disorder that causes your body to attack parts of your brain in response to gluten.

What should I do if I think I have a gluten problem?

Talk to a physician if you think gluten could be affecting your health. Your doctor may suggest blood tests to detect celiac disease or a wheat allergy. Before cutting gluten out of your diet, work with a registered dietitian to build an eating plan that’s right for you.

Gluten intolerance

Most people can tolerate gluten with no adverse effects.

However, it can cause problems for people with certain health conditions.

This includes celiac diseasegluten sensitivitywheat allergy, and some other diseasesTrusted Source.

Celiac disease

Celiac disease, also spelled as coeliac disease, is the most severe form of gluten intolerance. It affects about 1% of the population.

It is an autoimmune disorder in which the body treats gluten as a foreign invader. The immune system attacks the glutenTrusted Source, as well as the lining of the gut.

This damages the gut wall and may cause nutrient deficiencies, anemia, severe digestive issues, and an increased risk of many diseases.

The most common symptoms of celiac disease are:

However, some peopleTrusted Source with celiac disease may not have digestive symptoms but may have other symptoms, such as tiredness or anemia.

For this reason, doctors often find it challenging to diagnose celiac disease. In fact, in one study, 80%Trusted Source of people with celiac disease did not know they had it.

Non-celiac gluten sensitivity

Many people do not test positive for celiac disease but still react negatively to gluten.

This condition is non-celiac gluten sensitivity.

Researchers do not currently know how many people have this condition, but some estimate it to be in the range of 0.5–13%Trusted Source.

Symptoms of gluten sensitivity include:

  • diarrhea
  • stomach pain
  • tiredness
  • bloating
  • depression

There is no clear definitionTrusted Source of non-celiac gluten sensitivity. Still, a doctor may make this diagnosis when a person reacts negatively to gluten, but they have ruled out celiac disease and allergies.

However, some experts do not believe that this is a legitimate condition. They think that substances other than gluten cause these adverse effects.

One study looked at 392 people with self-diagnosed gluten intolerance and investigated whether they improved on a gluten-free diet.

The results showed that only 26 people had celiac disease, while two individuals had a wheat allergy. Only 27 of the remaining 364 people received a diagnosis of gluten sensitivity. That means that of all the participants who thought they had gluten intolerance, only 55 people (14%) had gluten issues.

Therefore, many people who think they have gluten intolerance may develop symptoms due to other causes.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common digestive disorder that causes symptoms, including:

  • abdominal pain
  • cramping
  • bloating
  • gas
  • diarrhea or constipation, or both

IBS is a chronic condition, but many people can manage their symptoms with diet, lifestyle changes, and stress management techniques.

ResearchTrusted Source has shown that some individuals with IBS may benefit from a gluten-free diet.

Wheat allergy

For an estimated 0.2–1%Trusted Source of the pediatric population, a wheat allergy may be causing digestive issues after consuming gluten. However, up to 65% find that these issues resolve without treatment as they reach adulthood.

People with a wheat allergy may still consume other foods that contain gluten, such as barley or rye, without experiencing an adverse reaction.

Furthermore, research shows that a gluten-free diet may benefitTrusted Source some individuals with schizophrenia. Other researchTrusted Source shows possible benefits for autism and also a disease called gluten ataxia.

Intolerance vs. sensitivity

Digestive discomfort is the most commonTrusted Source indication of gluten intolerance. The person may also have anemia or trouble gaining weight.

To determine the cause of the discomfort, people can ask their doctor to check for celiac disease first.

There are two main waysTrusted Source to determine if a person has celiac disease:

  • Blood tests: Several blood tests screen for antibodies. A common one is the tTG-IgA test. If that is positive, the doctor may recommend a tissue biopsy to confirm the results.
  • Biopsy from small intestine: A health professional takes a small tissue sample from the small intestine, which a lab analyzes for damage.

A person should undertake both of the above tests while following a gluten-containing diet. Performing the blood test while on a gluten-free diet will yield a false negative. This is because there is no gluten in the system to trigger antibody production.

If a person thinks they may have celiac disease, they should consult their doctor before trying a gluten-free diet.

If the person does not have celiac disease, the best way to find out if they are sensitive to gluten is to follow a strict gluten-free diet for a few weeks to see if symptoms improve.

Then, they will need to introduce gluten back into their diet to see if their symptoms return.

If the person’s symptoms do not improve on a gluten-free diet and do not get worse when they reintroduce gluten, then the cause is probably something other than gluten.

A gluten-free diet test is not a definite way to diagnose the issue, and people should not try this on their own. If a person suspects they may have a problem, they should seek guidance from a healthcare professional who can test for celiac disease or allergies.

Gluten-free diet

Some people may find starting a gluten-free diet rather challenging.

The first thing a person needs to do is read the labels on everything they eat and drink.

Gluten, especially wheat, is an ingredient in a surprising number of foods. Gluten is also present in barley, rye, and any products that contain these ingredients, such as rye bread.

In this diet, people should eat mainly healthy whole foods, as most whole foods are naturally gluten-free. Avoid processed food, cereals, and grains that contain gluten.

Gluten-free grains

Several grains and seeds are naturally gluten free and available to purchase online. These include:

However, while oats are naturally gluten free, cross-contamination can occur if a facility processes oats alongside other gluten-containing grains such as wheat. Therefore, it is safest only to consume oats with a gluten-free label.

Gluten-free foods

There are plenty of healthy whole foods that are naturally gluten free, including:

  • meat
  • fish and seafood
  • eggs
  • dairy products
  • fruits
  • vegetables
  • legumes
  • nuts
  • tubers
  • fats, such as oils and butter

It is generally better for people to choose naturally gluten-free food rather than processed gluten-free products. These tend to be low in nutrients and high in added sugar or refined grains.

Most beverages are also gluten free, except beer unless labeled gluten free.

Various gluten-free recipe books are available to purchase online. Many gluten-free foods are also available online, including gluten-free bread and gluten-free snacks.

Read about which foods are gluten-free here.


FODMAPs are short-chain carbohydrates found in many foods, including wheat.

Many people cannot digest these properly, which can causeTrusted Source various digestive symptoms.

There is some evidence that people with “gluten sensitivity” may be sensitive to FODMAPs, not gluten.

2018 study looked at the effect of fructans, a type of FODMAP, in 59 people who self-reported gluten sensitivity but did not have celiac disease. Researchers found that a fructans diet caused significantly higher gastrointestinal symptoms than gluten consumption. This indicates that FODMAPs may be the culprit for some people who think they react negatively to gluten.

Doctors may recommend that people with IBS follow a low-FODMAP diet. However, many people find this difficult to do, and if a person does not do this correctly, this diet may lead to several nutrient deficiencies. Therefore, people should follow this diet with the help of a healthcare professional.

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