Is gluten free just another fad?  Gluten-free products are flying off grocery shelves, and restaurants are boasting of meals with no gluten. Celebrities on TV talk shows chat about the digestive discomfort they blame on the wheat protein they now shun. Some churches even offer gluten-free Communion wafers. “I don’t know whether there’s more people getting this or that more people are noticing” they have a problem, said the Rev. Richard Allen, pastor at Mamaroneck United Methodist Church, north of New York City. Americans will spend an estimated $7 billion this year on foods labeled gluten-free, according to the market research firm Mintel. But the best estimates are that more than half the consumers buying these products — perhaps way more than half — don’t have any clear-cut reaction to gluten.  Takeaway for marketers: consumers are looking for healthier foods and gluten-free is an easy way for them to navigate through thousands of products to get there.