Updated August 12, 2026

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? A Johns Hopkins Medicine specialist in internal medicine/pediatrics 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. It 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.

Some researchers have explored whether people with certain digestive symptoms may have increased intestinal permeability, sometimes called a “leaky gut.” In some cases, the lining of the small intestine may allow more substances to pass through than usual. However, the idea that undigested gluten or other particles routinely enter the bloodstream and cause inflammation in otherwise healthy people is not well established.

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. “Humans have been consuming gluten for thousands of years, and gluten-containing foods like whole grains can provide protein, fiber and important nutrients.”

Gluten itself is not harmful for most people who can tolerate it. The bigger issue is often the quality of the foods that contain it. Refined grain products, such as white bread, many crackers and baked goods, are often made with processed flours and may be low in fiber and nutrients compared with whole grains.

“Whole grains are highly nutritious,” explains Rajagopal. “They contain fiber and important vitamins and minerals, while refined grains have had much of that removed.”

Many people who adopt a gluten-free diet but continue eating processed foods may still experience weight gain, blood sugar swings and other health issues. In those cases, it’s usually the overall diet — including excess sodium, sugar and calories — rather than gluten itself, that’s contributing to the problem.

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?

If you think gluten could be affecting your health, talk to a physician. 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.

Medically reviewed by Selvi Rajagopal, M.D., M.P.H.