As many as 20 million Americans are suffering unnecessarily.

If you’ve always assumed that gluten-free foods are for someone else, it may be time to reconsider. Scientists are now finding that many more people than once believed are suffering ill effects from bread, cereal, pasta and other foods that contain gluten.

Until recently, most doctors thought that you could safely consume gluten unless you had celiac disease, an autoimmune disorder that damages the intestine and causes symptoms such as abdominal pain, bloating, chronic diarrhea and/or foggy thinking.

Now: An international panel of experts recently concluded that millions of Americans who do not have celiac disease also could benefit from giving up gluten. A new classification system, published in the peer-reviewed online journal BMC (BioMed Central) Medicine, now identifies gluten sensitivity as a distinct disease, one that’s related to, but not the same as, celiac disease.

It’s an important distinction because people who tested negative for celiac disease in the past often were told that they didn’t need to give up gluten, even when their symptoms were virtually identical to those of celiac patients. Some doctors even insisted that the symptoms were imaginary—and that these patients should get psychiatric help.

Gluten sensitivity also can lead to other conditions, such as irritable bowel syndrome (IBS), fibromyalgia and chronic fatigue syndrome.

We now know that gluten sensitivity is not only real but common, possibly affecting about 5% to 7% of Americans. Celiac disease affects about 1%. Could gluten be affecting you—and you don’t even know it?

WHAT’S THE DIFFERENCE?

If you have celiac disease or gluten sensitivity, your immune system reacts to gluten—but in different ways…

With celiac disease, gluten triggers the activation of the immune system, which mistakenly attacks the small intestine. A similar process is involved in other autoimmune diseases, such as rheumatoid arthritis and lupus.

If you have celiac disease and eat gluten, the immune system attacks villi, hairlike projections in the small intestine that absorb nutrients. Abdominal discomfort and digestive problems, including the malabsorption of essential vitamins and minerals, can result.

The symptoms can differ among celiac patients—some may have sharp abdominal pains that come and go…others could experience a chronic squeezing ache. They also can have a higher risk of developing intestinal cancer or neurological disorders, such as migraines and peripheral neuropathy.

With gluten sensitivity, a part of the immune system known as the innate immune system is affected. Unlike people with celiac disease, those with gluten sensitivity don’t produce antibodies to gluten, nor do they suffer damage to the small intestine or have a higher-than-average risk for cancer. They do have an immediate reaction to gluten—the body releases inflammatory substances that can cause abdominal pain and other symptoms similar to those seen in celiac disease.

Similarly, a person who has a wheat allergy can have many of the same symptoms of celiac disease or gluten sensitivity. With a wheat allergy, however, the patient may have an itchy skin rash, asthma or even, in extreme cases, anaphylaxis, a severe, whole-body allergic reaction that can be life-threatening.

A GROWING THREAT

The incidence of celiac disease has quadrupled in about the last half-century. Researchers suspect that gluten sensitivity has increased at a similar rate. The reasons for these increases aren’t yet known.

One possible explanation is that our bodies haven’t had time to adapt to the processed foods and the increased gluten content found in several grains during the last 50 years. As a result, the immune systems in people genetically predisposed to gluten-related disorders may not recognize these foods as “friendly.”

WHEN TO SUSPECT GLUTEN

Many people with celiac disease or gluten sensitivity eventually see a diet-related pattern to their symptoms—they feel worse when they eat such foods as bread and pasta.

Good news: The symptoms of both celiac disease and gluten sensitivity typically disappear following the adoption of a gluten-free diet. With celiac disease, symptoms may improve within a few weeks, although the intestinal damage may take several months or even years to completely heal. If you’re sensitive to gluten, the relief can be much faster, often within a few days.

WHAT TESTS DO YOU NEED?

If you suspect that you have celiac disease, get tested before giving up gluten-containing foods. People with celiac disease who quit consuming gluten will have a false-negative blood test—it will show that they don’t have the disease even if they really do. Here’s how celiac disease is detected…

Blood test. This is a simple and an accurate way to identify two antibodies, anti-endomysium and anti-tissue transglutaminase, that are produced when patients are exposed to gluten.

Biopsy. A diagnosis of celiac disease (but not gluten sensitivity or a wheat allergy) can be verified with a biopsy. It’s done by endoscopy, which involves the insertion of a thin tube through the mouth, esophagus and stomach and into the small intestine. A small piece of tissue is removed and examined in a laboratory to look for damage to the villi. Those with gluten sensitivity or wheat allergies will not have damaged villi.

There are no reliable tests for gluten sensitivity. The condition is a diagnosis of exclusion—your doctor will say that you have gluten sensitivity if you test negative for celiac disease and a wheat allergy (diagnosed by a skin prick or blood test), but your symptoms and personal history indicate gluten is the problem.

GO GLUTEN-FREE

If you have celiac disease, you must avoid all obvious and hidden sources of gluten for life. Widely recognized sources of gluten are wheat, barley and rye, and lesser-known sources include bulgar and spelt (both forms of wheat).

Ask your doctor for a referral to a licensed dietitian to help you adhere to the gluten-free diet. Read food labels to learn which packaged foods contain gluten, and join a support group in your area to learn about gluten-free resources. For a list of gluten-free foods, go to Celiac.org…or to get recipes, go to Gluten.net. For more information on gluten-related disorders, go to CeliacCenter.org.

If you have gluten sensitivity, you also may need to follow a gluten-free diet. However, some people with gluten sensitivity can tolerate small amounts of gluten, such as a few bites of pizza or a taste of bread. In some cases, tolerance can change over time.

Caution: If you have celiac disease, even trace amounts of gluten can trigger a reaction. For example, foods without gluten, such as oats, can cause a problem for celiac sufferers if gluten-containing foods are processed on the same machinery.

What Is GLUTEN?

Gluten is a protein that occurs naturally in wheat, barley and rye—as well as in bulgar and spelt (forms of wheat). Breads, cereals, pastas and cakes are among the foods that typically contain gluten. It also can be found in thousands of processed foods, including salad dressings, ice cream, yogurt and soup (in the form of ingredients such as “filler flour,” “vegetable starch” and “hydrolyzed wheat gluten”).