If you've found that you are sensitive to gluten — the stretchy protein that makes wheat bread fluffy and pie crusts crisp – perhaps you've had to bear the brunt of the gluten-free backlash.

Some 47 percent of American consumers say the gluten-free diet is a fad, according to Mintel research. And that's partly because there's been scant proof of what causes non-celiac gluten sensitivity. As far as diagnosing it goes, there's nothing akin to the gold standard tests that help diagnose the one percent of the population that has celiac disease.

But those who shun gluten (and don't have celiac disease) may not be food faddists after all. Researchers are finally homing in on markers for gluten sensitivity in the body. A study from Giovanni Barbara and his team at the University of Bologna, Italy, suggests that gluten sensitive individuals may harbor high levels of a molecule called zonulin that is linked to inflammation

Levels of zonulin in the blood have already shown to be high in celiacs. In Barbara's study, levels in gluten-sensitive individuals almost matched those of celiacs. Though the results are preliminary, they point in a hopeful direction for future tests to help diagnose this controversial condition.

About 6 percent of the global population may be sensitive to gluten, according togastroenterologist Alessio Fasano of Massachusetts General Hospital in Boston. Symptoms can be similar to irritable bowel syndrome, with abdominal pain, bloating, alternating diarrhea or constipation. And there can be other symptoms, including "brain fog", headache, fatigue, joint and muscle pain.

Enter zonulin, stage left. Zonulin is an inflammatory protein first discovered by Fasano and his team in 2000. It helps regulate leakiness in the gut by opening and closing the spaces or "junctions" between cells in the lining of the digestive tract. Zonulin is triggered by harmful bacteria, and offers important protection to the body: If you accidentally eat a food contaminated with salmonella, you rely on zonulin to help trigger diarrhea and flush out the bugs.

Once the pathogen is gone, zonulin levels drop and the junctions close. 

So what does it have to do with gluten? It turns out that gluten is a strong trigger of zonulin in some individuals. "No human being completely digests gluten," says Fasano. "And in a small percentage of us, that undigested gluten triggers the release of zonulin," leading to high levels of it. - Read More at NPR

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