Dunkin\' Donuts said Thursday it would introduce a gluten-free cinnamon sugar doughnut and a gluten-free blueberry muffin by the end of the year. \"At Dunkin\' Donuts, we recognize the importance of providing our guests with many options, including alternative choices for people with food and dietary restrictions,\" Michelle King, a spokeswoman for Dunkin\' Brands, said in a statement. \"We understand that sensitivities to food ingredients such as gluten are a serious concern for certain guests, so we plan to introduce a gluten-free cinnamon sugar donut and a gluten-free blueberry muffin that will be available as an option at participating Dunkin\' Donuts restaurants.\" The new products are already for sale in a few Hartford, Conn., stores, Dunkin\' Donuts said. Health officials estimate 1-in-135 people are thought to have celiac disease, but many more avoid gluten because they think it is healthier to do so. \"It\'s great for celiac people to feel that they can go into a shop with everyone else and buy something,\" Jan Phillips, co-founder of the website Gluten Freedom Project, told the Los Angeles Times. \"But on the other hand, someone with celiac disease does need to eat healthfully.\" Celiac disease is an immune reaction to eating gluten, a protein found in wheat, barley and rye. Eating gluten triggers an immune response in the small intestine and over time, this reaction produces inflammation that damages the small intestine\'s lining and prevents absorption of some nutrients.