The Los Angeles Times reports:
With one-third of Americans trying to avoid the protein, the "gluten free" label holds increasing cachet. On Friday, the federal government issued an official definition of that claim, bringing a measure of uniformity to a burgeoning industry.
According to the Food and Drug Administration, a food or other substance can be labeled "gluten free," "no gluten," "without gluten" or "free of gluten" if contains less than 20 parts per million of it. Manufacturers have until Aug. 5, 2014, to comply with the new definition.
Some parents believe their children's autism symptoms improved when they stopped eating gluten and casein (a protein found in milk products), though there's no scientific evidence to support their observations.
See the FDA release.