SAN ANTONIO -

When you buy food labeled "gluten-free", you should soon know exactly what you're getting.

The Food and Drug Administration announced  new labeling rules, defining what "gluten-free" means. 

The new standard says a product must contain fewer than 20 parts per million of gluten to carry the gluten-free label.

Until now, it has been up to the manufacturer's discretion as to how much gluten is in their food.  

"That really does help us," said Garrett Greenblum, an Alamo Heights High School senior who lives with celiac disease. Shopping for safe foods can be painstaking.

"I have to watch everything I eat, because if I do eat gluten, I have a pretty immediate reaction to it," he said.

An estimated  three million Americans have Celiac Disease, a condition  that prevents the person from digesting gluten. Eating gluten can lead to intestinal damage.

Gluten is found naturally in grains like wheat, barley and rye.  

Under the new rule, foods labeled "gluten-free"  or terms of similar meaning, won't technically have to be 100 percent gluten free.  The amount still allowed, fewer than 20 ppm, is low enough that most people who have celiac disease won't get sick, according to the FDA.

Companies have one year to conform with new labeling rules.