Papa John's has added gluten-free pizza to the menu, but those with celiac disease or gluten intolerance should steer clear.

The pizza chain on Monday said the new pizza crust contains sorghum, teff, amaranth and quinoa and is made in a separate facility before being shipped to stores nationwide.

However, Papa John's doesn't recommend that diners with celiac disease or a serious gluten intolerance purchase that new crust. The company said that it is possible that the gluten-free crust could come into contact with gluten in its restaurants.

"Although Papa John's Ancient Grains Gluten-Free Crust is gluten-free and Papa John's employs procedures to prevent contact with gluten, it is possible that a pizza with Papa John's Ancient Grains Gluten-Free Crust is exposed to gluten during the ordinary preparation process," the company told CNBC. "Please use your best judgment in ordering a pizza with Papa John's Ancient Grains Gluten-Free Crust if you have a sensitivity to gluten."

Papa John's isn't the only national pizza chain to offer a gluten-free crust that might not be suitable for gluten-intolerant diners. Domino's warns customers with celiac that there is a risk for gluten exposure in restaurant kitchens and that "customers with gluten sensitivities should exercise judgment in consuming this pizza."

The Celiac Disease Foundation estimates that one in 100 people worldwide have celiac disease, an autoimmune disorder where the ingestion of gluten leads to damage in the small intestine.

"If Papa John's has a gluten-free crust but is suggesting that folks who have celiac or gluten intolerance stay away from it then it's very confusing," Nikki Ostrower, a nutritional expert and owner of NAO Nutrition, told CNBC via email. "Anytime a company advertises that a product is gluten-free then anyone who has celiac or gluten intolerance should be able to enjoy it. It sounds like Papa Johns is trying to get in on the gluten-free craze in an inauthentic way."

Gluten-free food sales have grown 178 percent between 2013 and 2016, according to Mintel research, although most of this growth may not be coming from the celiac community. Many diners have swapped to diets where they eat fewer carbs and have embraced gluten-free menu items, spiking demand.

In the last two years, the number of gluten-free foods on menus has grown 61 percent, according to Technomic's MenuMonitor data.