Traditionally brewed soy sauce: Is it actually free of gluten peptides?

You may have read recently on social media that the Norwegian Celiac Association stated that traditionally brewed, wheat-based soy sauce is free of gluten and gluten residues. They joined Sweden and Finland in this assessment. For more information on what led to this conclusion, see https://ncf.no/glutenfri-mat/kosthold-og-ernering/vanlig-soyasaus-er-glutenfri-og-kan-brukes-av-de-med-coliaki

Believe it or not, the FDA arrived at a somewhat similar but more conservative conclusion in the health hazard assessment they conducted on Chef Myron’s sauces containing wheat-based soy sauce. Gluten Free Watchdog asked the FDA for years to recall the sauces (eventually the FDA recalled 9 sauces). However, it was a level 3 recall—meaning the products were in violation of the rule but were unlikely to cause adverse health consequences.

Note: The health hazard assessment is not in the public domain. We learned about it based on a FOIA request.

The information below was previously published on Gluten Free Watchdog but it is worth another read if this topic is of interest.

Health hazard assessment bottom line: There is some evidence to suggest that there are low to absent levels of gluten in most commercial soy sauces. In addition, because soy sauce is a condiment it is likely to be consumed in small amounts. Regardless, it is not possible to know the concentration level of wheat gluten or gluten residues in final product soy sauce due to limitations in current testing methodologies for fermented foods. Therefore, gluten levels must be assessed prior to fermentation.

Health hazard assessment details: The assessment provides a window into FDA’s thinking on soy sauce (paraphrased from the health hazard assessment):

1. Soy sauce is generally made via the fermentation of wheat and soybeans.
2. Fermentation is not considered a process to remove gluten.
3. Fermentation may break apart gluten protein into smaller gluten protein fragments.
4. Current testing methods may not accurately measure the amount of gluten in fermented products.
5. The part per million level of gluten in soy sauce after fermentation can’t be reliably estimated.
6. Gluten levels in fermented foods must be assessed before fermentation.
7. A literature review found some evidence to suggest that wheat-containing soy sauces may be tolerated by wheat-allergic individuals.
8. The health hazard posed by undeclared wheat gluten or immunogenic gluten residues depends on the exposure amount in the final product consumed per meal.
9. Wheat gluten/gluten residues at levels above 20 ppm are likely to pose a risk to individuals with celiac disease and wheat allergy.
10. Wheat gluten/gluten residues at levels below 20 ppm could pose a “remote hazard” for some highly sensitive consumers with wheat allergy.
11. Based on published data analyzing soy sauce using ELISA and Western Blot methodology, soy sauce fermentation may remove a substantial amount of wheat protein peptides.

Given that both the FDA and Norway conducted a review of the scientific literature, why is the FDA’s stance more conservative than Norway’s? There are two main reasons…

1. The FDA is not a fan of the competitive R5 ELISA—the assay used to detect gluten protein fragments in foods that are fermented or hydrolyzed. The FDA states that they know of “no scientifically valid analytical method effective in detecting and quantifying with precision the gluten protein content in fermented or hydrolyzed foods in terms of equivalent amounts of intact gluten proteins.” According to the FDA, the R5 Competitive ELISA method is not suitable for the detection and quantification of gluten in any fermented or hydrolyzed food. The FDA stresses that the inability to detect any gluten using the R5 Competitive ELISA is not an indication of complete elimination or even a reduction of gluten. The R5 antibody does not recognize all immunogenic amino acid sequences. Gluten could be present in a form that is not detectable by the competitive R5 ELISA.
2. Due to the FDA’s position on the competitive R5 ELISA, under the FDA’s gluten-free labeling rule for fermented or hydrolyzed foods and ingredients, fermented and hydrolyzed ingredients in foods carrying a gluten-free claim must be gluten-free as defined by the 2013 gluten-free labeling rule before fermentation and hydrolysis.

For more information on the FDA and testing, please see https://www.glutenfreewatchdog.org/news/what-the-fda-has-to-say-about-testing-for-gluten/

Where does this leave us? First and foremost, in the US, products containing wheat-based soy sauce that are labeled gluten-free are misbranded. Manufacturers must follow the FDA’s gluten-free labeling rule. That said, just because we may not be able to accurately test something for gluten doesn’t mean it contains gluten. Might traditionally brewed soy sauce be free of gluten protein fragments? Maybe. Does this mean you should routinely use this product? Probably not—at least not until better testing is available.