Those who avoid gluten may not be food faddists after all. Researchers are finally homing in on markers for gluten sensitivity in the body. JPM/Getty Images hide caption toggle caption JPM/Getty Images The Salt A Protein In The Gut May Explain Why Some Can't Stomach Gluten December 9, 2015 Some people who don't have celiac disease say they feel better on a gluten-free diet. Researchers have long been puzzled as to why. A study suggests it could be because of a protein called zonulin.