Gluten Detective: Consumer Test Kits for Detecting Gluten in Stool and Urine
Posted January 10, 2018
Note: Gluten Free Watchdog purchased the tests shown in the photo from Glutenostics. All conversations with Glutenostics have been “on the record.”
There are two new consumer tests for monitoring gluten intake on the market from Glutenostics—Gluten Detective stool test and Gluten Detective urine test. According to the manufacturer these tests can be used to monitor “major transgressions” related to gluten intake (urine test) and “total weekly gluten consumption” (stool test). What follows is information about the amount of gluten (and what this looks like) that has to be eaten for either test to detect gluten.
Please note that this discussion is not about whether these tests work or whether they should be used. Both tests are based on the 33-mer peptide. This peptide is considered immunogenic to folks with celiac disease and according to Romer labs (not affiliated with Glutenostics), “is highly resistant to digestive degradation and is therefore well suited as an analytical marker.” Research assessing the stool and urine tests has been published in the scientific peer review literature.
Urine test (from the manufacturer):
Minimum intake 500 mg
Per manufacturer: 2 bites of bread
Optimal window 6 to 16 hours (full window 1 to 24 hours)
Stool test (from the manufacturer):
Minimum intake: 50+mg
Per manufacturer: a crumb of bread
Optimal window: 2 to 4 days (full window 1 to 7 days)
Question: Will the stool test detect gluten eaten from labeled gluten-free food or food that appears to be free of gluten-containing ingredients when the gluten level is greater than 20 ppm gluten?
Keep in mind the following:
- 1 ounce of a product with a gluten level of 2,000 ppm contains approximately 50 mg of gluten.
- 2 ounces of a product with a gluten level of 1,000 ppm contains approximately 50 mg of gluten.
- 4 ounces of a product with a gluten level of 500 ppm contains approximately 50 mg of gluten.
- 10 ounces of a product with a gluten level of 200 ppm contains approximately 50 mg of gluten.
- 20 ounces of a product with a gluten level of 100 ppm contains approximately 50 mg of gluten.
- 40 ounces of a product with a gluten level of 50 ppm contains approximately 50 mg of gluten.
- 80 ounces of a product with a gluten level of 25 ppm contains approximately 50 mg of gluten.
Based on the above information, it seems unlikely that gluten will be detected from a food labeled gluten-free that is not in compliance with the gluten-free labeling rule (< 20 ppm gluten) unless the food is highly contaminated and/or a lot of the food is eaten over the course of 2 to 4 days.
Question: Will the stool test detect gluten cross contact, such as from breadcrumbs on a cutting board?
- Assuming the crumbs are from wheat bread that has a gluten level of 124,000 ppm, the equivalent of 1/70th of a one-ounce slice of wheat bread crumbs would have to be eaten to ingest 50 mg of gluten.
- What does this look like?
- Measuring 1/70th of one ounce of my husband’s bread, it looks a bit smaller than a dime (see photo).
- What does this look like?
1/70th of a one-ounce slice of bread amounts to quite a few crumbs. But it is plausible that accidental cross contact with wheat-based bread, pasta, or flour could result in this level of intake, especially over 2 to 4 days. However, characterizing 50 mg of gluten as “a crumb of bread” (as is done by the manufacturer) is not quite accurate.
How much gluten would you have to eat for the urine test to be positive?
- About 1/7 of an ounce of wheat bread, assuming a gluten level of 124,000 ppm.
The urine test seems more useful for assessing whether or not regular bread or pasta was accidentally eaten (as is insinuated by the manufacturer).
What I would like to see
In the US, we tend to use 10 mg of gluten per day as the “safe” threshold for folks with celiac disease. If the optimal window for the stool test is 2 to 4 days, it would be useful if the lower limit of detection for this test could be reduced from 50 mg to 20 to 40 milligrams of gluten.
If you are concerned that you have been regularly exposed to cross contact from gluten over a period of days then you may find the stool test useful (assuming the test works as the manufacturer claims). However, if you are concerned that a single food or meal may have contained a level of gluten above 20 ppm, this test will likely not provide you with an answer (unless the food/meal is highly contaminated).
Statement from Glutenostics
A draft of this post was shared with Glutenostics prior to publication. They were invited to provide a comment for publication. Their statement is posted in full.
“The FDA has determined the safe level of gluten concentration in food to qualify as ‘gluten-free’ to be 20 ppm (20 mg gluten per 1 kg food). Based on the fact that the average American eats 4.5 pounds = 2.5 kg of food per day, the maximum amount of gluten that the average American could consume while eating foods labeled ‘gluten-free’ is 50 mg of gluten per day (20 ppm x 2.5 kg food = 50 mg gluten). Gluten Detective recognizes that the definition of a ‘crumb’ is subjective, and is dependent on the density of the bread, which may be ‘fluffy’ resulting in a bigger crumb such as that shown in the image here, or more dense resulting in a smaller crumb (not shown).”