Store aisles, markets, bakeries, blogs and books are stocked with food ideas for going gluten-free. The gluten-free diet has become popular for combating a full-blown gluten rejection known as celiac disease, or more popularly for those with no intolerance at all as a means to lose weight and enhance athletic performance.
But researchers say there's a middle ground emerging. A growing number of people now have a type of gluten intolerance called nonceliac gluten sensitivity, which isn't quite as serious as celiac disease but not to be taken lightly either. Mounting evidence now suggests the number of people who have nonceliac gluten sensitivity may outnumber those who have full-blown celiac disease.
Celiac disease is a genetic condition that damages the lining of the small intestine and prevents it from absorbing nutrients from food. The damage is attributed to an autoimmune reaction to eating gluten, a protein found in wheat, barley, rye and possibly oats.
People with celiac disease are diagnosed through specific blood and bowel tests. Those with the disease have a higher risk for anemia, osteoporosis, severe intestinal damage and gastrointestinal cancers.
Unlike celiac disease, gluten sensitivity walks a blurry diagnostic line. There's no definitive way to diagnose the condition like a blood test. The condition is also not associated with as serious side effects and doesn't have the same genetic markers as celiac disease.
"It's been very tough to qualify and classify given that we did not have a clear definition of what it's all about," said Dr. Alessio Fasano, director of the Center for Celiac Research at the University of Maryland School of Medicine. In February, Fasano and more than a dozen international immunology experts published a consensus report identifying gluten sensitivity as one in a group of gluten spectrum disorders that include wheat allergy and celiac disease.
Sixty million gluten-free products are consumed in the U.S. each day, Fasano said. But the question remains as to how many of these products are consumed out of necessity.
What looks like an increase in the number of people reporting gluten sensitivity may stem from an incorrect diagnosis, according to Italian researchers who published a commentary Monday in the Annals of Internal Medicine
Since there are no standard diagnosing criteria for gluten sensitivity, few patients have been properly diagnosed, the researchers wrote.
"We don't have agreement about what gluten sensitivity is all about," said Fasano, who did not write the commentary.
Common symptoms of gluten sensitivity include abdominal pain similar to irritable bowel syndrome, fatigue, headaches and a "foggy mind." But these symptoms generally improve or disappear after removing gluten from the diet.
"There's people who will claim they have it but when we're looking for sensitivity, we're looking for cause and effect," said Fasano, adding that for many, it's hard to prove that consuming gluten is the actual cause of these symptoms. Researchers estimate that 5 percent to 6 percent of those who claim they have gluten sensitivity actually have it.
One of the best ways physicians can try to diagnose the condition is to perform individual gluten challenge tests -- much like food allergy scratch tests -- rather than relying on self-reported symptoms, the researchers wrote.
But the holy grail to decoding nonceliac gluten sensitivity, one that Fasano and other researchers are on the hunt for, is finding a biomarker to detect the condition.
Then, a simple test can give experts the answers, "so we can do what I believe to be modern medicine," said Fasano.