The young grasses of these plants are not the same as the grains (that contain gluten) found when the plant matures. For this reason, the Food and Drug Administration will allow wheat or barley grass (or grass juice) as an ingredient in a labeled gluten-free product as long as the final product contains <20 parts per million gluten, INCLUDING the presence of any gluten due to cross contamination with gluten-containing grains.
If a person with a gluten-related disorder wants to consume a labeled gluten-free product that contains wheat grass or barley grass, it is recommended that he/she verify the manufacturer is testing for gluten contamination using the R5 ELISA test.1
BOTTOM LINE: It is very difficult to guarantee that wheat or barley grass is 100% free of seeds, in other words, absolutely pure and free of gluten. My own recommendation is to avoid products with wheat grass or barley grass (or their juices) even if they are labeled gluten-free and being tested with the R5 ELISA for gluten. It’s easy to find a similar product that does not contain wheat or barley grass (or juices) to avoid these potentially risky ingredients. Overall, whole fruits and vegetables contain better sources of vitamins and minerals and are less expensive.
And add this link instead with reference #1 in front of it:
1. Gluten Free Dietitian. https://www.glutenfreedietitian.com/can-products-containing-wheat-and-barley-grass-be-labeled-gluten-free/
Revised and published online October 2, 2018.
Note: This information is provided by NCA and Melinda Dennis, NCA's Senior Consulting Dietitian. This information is meant for educational purposes and is not intended to substitute for personalized medical advice or replace any medical advice provided directly to you by your health care provider. This information can be printed and used in consultation with your physician or dietitian. No liability is assumed by NCA, Ms. Dennis or her nutrition consulting service Delete the Wheat, LLC. by providing this information.