Tame Your Tummy Trouble

Will a Gluten-Free Diet Improve Your Health?

The spectrum of gluten intolerance
Experts now think of gluten intolerance as a spectrum of conditions, with celiac disease on one end and, on the other, what's been called a "no man's land" of gluten-related gastrointestinal problems that may or may not overlap. Dr. Leffler estimates, for instance, that half of the approximately 60 million people in the U.S. who suffer from irritable bowel syndrome (IBS) are probably sensitive to gluten. (Gluten allergies, which are similar to other food allergies, also fall on the spectrum but affect only about 0.1% of the population.)

Gluten intolerance of any kind—including celiac disease—is often underdiagnosed (or misdiagnosed) because it manifests itself in many and murky ways that can baffle doctors. People with celiac disease and gluten sensitivity usually have stomachaches, gas, and diarrhea—as do people with IBS. Celiac patients can also develop headaches, tingling, fatigue, muscle pain, skin rashes, joint pain, and other symptoms, because the autoimmune attack at the root of the disease gradually erodes the wall of the intestine, leading to poor absorption of iron, folate, and other nutrients that affect everything from energy to brain function. People with gluten sensitivity sometimes experience these far-reaching symptoms as well, though it's less clear why.

Gluten intolerance "starts in the intestines as a process, but doesn't necessarily stay in the intestines. It may affect other organs," says Alessio Fasano, MD, medical director of the University of Maryland Center for Celiac Research, in Baltimore.

Celiac disease can be definitively diagnosed using a two-step process: Doctors test the patient's blood for the presence of intestine-attacking antibodies activated by gluten, and, if those tests come back positive, they order a biopsy (or series of biopsies) to look for intestinal damage, any evidence of which confirms the diagnosis.

Gluten sensitivity, on the other hand, is a gray area that "lacks any defining medical tests," Dr. Leffler says. People who fall into this group exhibit the classic symptoms of celiac disease yet have no detectable intestinal damage, and test negative for certain key antibodies (though in some cases they may have elevated levels of others). Gluten sensitivity is a kind of "non-diagnosis," in other words—a diagnosis by default for those who don't have celiac disease but feel better on a gluten-free diet.

A recent study by Dr. Fasano and his colleagues offers some clues about what gluten sensitivity is, and how it differs from celiac disease. Although they show no signs of erosion or other damage, the study found, the intestines of gluten-sensitive patients contain proteins that contribute to a harmful immune response, one that resembles—but is distinct from—the process underlying celiac disease.

Blood tests that can diagnose gluten sensitivity by measuring these and other proteins are in the works, but they are still a ways off. "The reason we don't have tests yet is mainly because we don't have a clear definition of [gluten sensitivity]," Dr. Fasano explains.

Next Page: How much gluten is OK?