I have combined the above 2 questions to address wheat grass juice and barley grass in supplements.

Wheat grass or barley grass (and their juices) are the young (gluten-free) grasses of the wheat or barley plant. They are different from the wheat grain or barley grain that grow on the same plant and DO contain gluten. The Food and Drug Administration will allow wheat or barley grass as an ingredient in a labeled gluten-free product, including supplements, as long as the final product contains <20 parts per million (ppm) gluten, INCLUDING the presence of any gluten due to cross contact with gluten-containing grains.1 So, technically, the probiotic supplement in question above is correctly labeled if the product contains <20ppm gluten when tested.

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.1,2

I personally do not recommend wheatgrass or barley grass or their juices to my patients because of this risk of cross contact between the young grass and the grain seeds. 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. Please see my updated post on FDA’s stance on labeled gluten-free wheat grass, barley grass, and their juices:
Do wheat grass and barley grass contain gluten?

Note: there is a SEPARATE issue that involves barley as a possible growth medium for the bacteria used in probiotic supplements. To read more about how this affects the gluten-free consumer, please see references #3-5.:

  1. National Celiac Association. Ask the Dietitian. Do wheat grass and barley grass contain gluten?
  2. Gluten-Free Dietitian. https://www.glutenfreedietitian.com/can-products-containing-wheat-and-barley-grass-be-labeled-gluten-free/.
  3. Thompson T, Dennis M, Emerson L. Gluten-free labeling: are growth media containing wheat, barley, and rye falling through the cracks? J Acad Nutr Diet. 2017 Sep 1. http://www.sciencedirect.com/science/article/pii/S2212267217310663
  4. A summary of the Thompson, Dennis, Emerson article: https://www.glutenfreewatchdog.org/news/study-summary-gluten-free-labeling-are-growth-media-containing-wheat-barley-and-rye-falling-through-the-cracks/
  5. National Celiac Association. Ask the Dietitian.  What is GliadinX product (digestive enzyme supplement)?

Reviewed and updated October 4, 2022.