The popularity of gluten-free foods has exploded in recent years but it hasn't always been clear exactly what a food labeled "gluten-free" really means.
Under new rules set by the US Food and Drug Administration, all foods labeled "gluten-free," "no gluten," "free of gluten" and "without gluten" must all contain less than 20 parts per million of gluten.
"Adherence to a gluten-free diet is the key to treating celiac disease, which can be very disruptive to everyday life," FDA commissioner Dr. Margaret A. Hamberg said.
The FDA's new 'gluten-free' definition will help people with this condition make food choices with confidence and allow them to better manage their health."
Friday's announcement from the FDA is the last step in a 2004 law that required the agency to set standards for how much gluten could be found in foods labeled as gluten free.
Up to 3 million Americans suffer from celiac disease, an autoimmune condition in which the body treats gluten as an allergen.
People with celiac can get sick from the gluten found in wheat and other cereal grains like barley and rye.
The new guidelines won't require foods to be technically free of these grains but the level is low enough that very few people would get sick from eating them.
Food manufacturers have raced to provide gluten-free options for many popular foods like cereals, baked goods and pizzas.
Packaged Foods, a consumer market research company, said that sales of gluten-free products stood at $4.2 billion in 2012, nearly triple what they were in 2008, reports the New York Times.
The new label rules will be "fantastic," Andrea Levario, executive director of the American Celiac Disease Alliance told USA Today.
Right now when she buys food for her son, who has celiac disease, "if I pick up a product and it says 'gluten-free' I don't know what that means because there's no federal standard," Levario told the newspaper.
A full summary of the new guidelines was posted on the FDA's website.