Does soy sauce contain gluten?

Yes Short answer

Yes, in almost all cases. Traditional soy sauce is brewed from roughly equal parts wheat and soybeans, and unlike maltodextrin the wheat is not processed to remove its protein, so regular soy sauce, teriyaki sauce and Worcestershire sauce all carry gluten unless the label says otherwise. Tamari and sauces specifically marked gluten-free are the exception, not the rule.

Also appears on labels as: soya sauce, shoyu, naturally brewed soy sauce.

What soy sauce is and how it's made

Traditional soy sauce is made by fermenting a mash of cooked soybeans and roasted, cracked wheat with a koji mould, then ageing the paste as a salty brine (moromi) for months before pressing out the liquid. Wheat typically makes up close to half the grain content, not a minor addition. It appears in stir-fries, marinades, dressings, ready meals, gravies and stock, and — as the gluten guide on this site notes — in flavoured crisps and snacks where it is easy to miss. Teriyaki sauce and Worcestershire sauce use soy sauce or the same wheat-and-soy fermentation as a base and carry the same risk.

Why regular soy sauce still counts as containing gluten

Maltodextrin and wheat-based glucose syrup are gluten-free because the manufacturing process hydrolyses the starch and strips out the protein. Soy sauce is different: the wheat goes in largely whole, and fermentation breaks proteins down chemically rather than removing them. A 2017 peer-reviewed study found that standard ELISA and lateral-flow gluten tests could not detect gluten in commercial soy sauce, teriyaki sauce or Worcestershire sauce after the brine fermentation stage — but the authors were clear that this reflects the limits of the test, not proof every immune-reactive fragment is gone.

The FDA's 2020 final rule on fermented and hydrolyzed foods addresses exactly this gap: fermentation and hydrolysis are not accepted as processes that remove gluten, because current lab methods cannot reliably measure gluten once proteins have broken down that way. So soy sauce fermented from ordinary wheat cannot be labelled gluten-free regardless of what a test on the finished bottle shows. The only route to a genuine claim is wheat processed to below 20 mg/kg (20 ppm) gluten before fermentation, or leaving wheat out altogether.

How it's labelled in the EU/UK and US

• EU and UK: wheat is a mandatory allergen under Annex II of Regulation (EU) No 1169/2011, so any soy sauce brewed with wheat must declare it, usually as "soya sauce (contains wheat)" or by naming wheat directly.
• US: wheat is a FALCPA major allergen, so a US label must carry a "Contains: Wheat" statement for wheat-based soy sauce — a stricter rule than for barley, which is not a FALCPA major allergen.
• A "gluten-free" claim requires testing below the 20 ppm threshold in the FDA's rule (21 CFR 101.91), and, per the fermentation rule above, manufacturers must show the wheat was gluten-free before fermenting rather than relying on a test of the sauce itself.

Tamari and genuine exceptions

Tamari, the Japanese soy sauce originally a by-product of miso, is traditionally brewed with little or no wheat, and many tamari brands are wheat-free and gluten-free. That is a difference in recipe, not a guarantee: some commercial tamari still contains a little wheat, so check the label rather than assume from the name. A genuinely gluten-free soy sauce or tamari says so on the front of the bottle, and Coeliac UK keeps a list of specific verified products for this reason.

What to check, and using the app

Treat any bottle labelled simply "soy sauce" or "soya sauce" as containing gluten unless it is explicitly marked gluten-free or tamari with no wheat listed. The same caution applies to teriyaki sauce, Worcestershire sauce and any ready meal, marinade or stock that lists soy sauce as an ingredient without saying so on the front pack — ask your allergist if a specific imported or unlabelled product leaves you unsure. Allervibe reads the full ingredients list on a product, so it catches soy sauce even when the pack itself carries no gluten-free claim either way.

Sources

• Regulation (EU) No 1169/2011, Annex II — substances causing allergies (wheat as a mandatory allergen)
• eCFR — 21 CFR 101.91, Gluten-free labeling of food
• FDA — Final rule on gluten-free labeling of fermented and hydrolyzed foods
• Jackson et al., Detection of Gluten during the Fermentation Process To Produce Soy Sauce (Journal of Food Protection, 2017)
• Coeliac UK — Safe gluten free options for takeaways

Information is sourced from public regulatory bodies (EFSA, FDA, WHO) and is for reference only. Always read the package and consult a healthcare professional for medical advice.