The study was conducted by a team of PepsiCo Inc. and Quaker Foods and Snacks employees who published “Gluten-containing grains skew gluten assessment in oats due to sample grind non-homogeneity” in the peer-reviewed journal Food Chemistry. It was reported on by celiac disease expert Tricia Thompson, MS, RD of Gluten Free Watchdog.

The study found that gluten-containing kernels of wheat, barley or rye may contaminate oats, but are difficult to detect when testing samples of the oats for gluten. The difficulty arises when a portion of the oats are taken to test for gluten contamination. Currently, testing involves grinding the oats with the intention of evenly distributing any gluten that may be present throughout the sample. The study found that grinding the oats does not actually ensure that gluten is evenly distributed. In effect, several samples taken from the same batch of oats may show three different results: one may show no gluten contamination, the second may show gluten contamination below 20 parts per million (ppm) and the third may show over 20 ppm.

This variation in results means that oats thought to be gluten-free because they tested with under 20 ppm of gluten (the FDA’s guideline for labeling food “gluten-free”) could actually contain a dangerous amount of gluten for those with celiac disease or non-celiac gluten sensitivity (‘gluten sensitivity’).

You can read a more detailed summary of the study from Gluten Free Watchdog.