How Harmful is Soy Sauce on a Gluten Free Diet?

If you are on a gluten-free diet, note that usually soy sauce that is not labeled gluten-free contains wheat. In some countries outside the United States, it may contain barley. While there are gluten-free brands of soy sauce on the market, including tamari sauce, you should know what to expect if you accidentally ingest some glutenous soy sauce.

Image: Soy Sauce and Soy Beans

There are two different methods of making soy sauce. The one used in making the most flavorful soy sauce is fermentation. The other process is chemical hydrolysis, where 3-MCPD occurs, which is a known carcinogenic (cancer-causing agent). Once processed, molasses or caramel color is added to make it darker in color.

In a soy sauce study, 22 brands of gluten-containing soy sauce were tested for gluten content from grocery stores and Asian markets using the R5 sandwich assay test or the R5 competitive ELISA test. All of the soy sauces tested with the R5 sandwich assay proved to be negative for gluten content. The ones tested using the R5 competitive ELISA test showed that 21 contained less than 20 parts per million (ppm) gluten and the other contained 22.8 ppm.

The United States limit of gluten in a gluten-free product may contain less than 20 ppm. If you do accidentally consume soy sauce, realize that if little is used in the recipe, it is most likely that you will not have a gluten reaction from the soy sauce, unless you are extremely sensitive to gluten. Also, if a small amount is used in what you consume, that amount compared to the volume of the food item brings the ppm down even further.

I am not suggesting to anyone that is gluten intolerant or on a gluten free diet to start consuming gluten-containing soy sauce. Just note that if you should accidentally ingest some, and you may have a reaction to it. The reaction could be due to you being hyper-sensitive to gluten, from the chemical hydrolysis process, or the testing of soy sauce is inaccurate. Some people are even sensitive to fermented products in general.

The FDA plans on releasing separate gluten-free labeling laws on fermented and hydrolized food.

Visit Carla’s Gluten Free Online Store.

20 Replies to “How Harmful is Soy Sauce on a Gluten Free Diet?”

  1. My kids have very severe gluten allergy. I also use Choseon soy sauce (조선 간장, brand name Sampyo) which is Korean soy sauce which has no wheat ingredient. It is our traditional way to make soy sauce and it is also gluten free.

  2. If you do end up ingesting gluten L-Glutamine supplements decrease the inflammation. Any time I ingest gluten and start to become in pain, I use this and I feel better within the next day. Worth checking out!

  3. So nice post! In Sweden the health authorities has come to the same conclusion (without going into details) that most soy sauces with wheat flour in the declaration contains less than 20 ppm That makes me wonder why many people are writing about south east Asia (or Asia in general) as a a hard destination to travel gluten free cause of the abundant use of soy sauce.

  4. pro tip I just made up:Drink plenty of water with food containing soy sauce to further dilute it :)

  5. This is such an informative post and comment section! Thank you for pulling together some sources and evidence-based information. A lot of the information I find when I google “eating soy sauce while gluten intolerant/sensitive” are just gluten free soy sauce recommendations or recipes to imitate the taste of soy sauce. Your post was the first one that actually answered my question of the likelihood of a reaction if accidentally consuming soy sauce. Thank you, Carla!

  6. Gluten Flam, made by Apex Energetics will negate the effects of a small amount of gluten, as in soy sauce. It has digestive enzymes specific to gluten. I take it with me anytime I eat out in Asian restaurants in case I accidentally have some. For me it has bee very effective.

  7. I got gluten poisoning from soy sauce I was told was gluten free. I could not touch solid food or stand up straight for almost all of 4 months and previously ( off of a millimeter of fake crab meat) it was 9 months of my stomach so swollen I looked like I was 8 months pregnant and I was in extreme pain the whole time. Needless to say this is devastating and causes intense pain, severe malnourishment, missed auditions and lost jobs . The only reason the last time was 4 months is because I did extreme and expensive things try to heal it. Now, I think it’s happened again, but this time I saved the suspected soy sauce culprit. How can I have this tested? I’m out for blood this time! Please, I would truly love a response!!! I’m sick of being assured something is gluten free, being shown the bottle and still having them give me the stuff containing gluten even after I tell them the consequences are deadly!!!

    1. Carrie,

      That’s terrible! Thank you for sharing your story.

      Just Foogle “Gluten test kit”. You’ll find many choices.


  8. How about Tamari sauce? I use it instead of soy sauce and I haven’t had any reactions to that. Seems to be a very good replacement.

  9. Has anybody who is celiac and eaten soy sauce and had a reaction? Really would like to know.

    I read the study described here, but it’s very likely that the R5 kit just cannot detect gluten in soy sauce, because it’s hydrolyzed. It doesn’t mean that we don’t respond to it as a celiac patient.

    Many test kits are known to not work with hydrolyzed products.

    1. Hi Claire,

      You are correct. As stated in the article, I list the inaccuracy of testing for gluten in hydrolyzed and fermented products. This is why the FDA will be publicizing separate guidelines for these types of products.

      I read an article by Dr. Vikki Petersen, author of The Gluten Effect, stating many of her patients react to soy sauce when consumed in Asian restaurants. She assumes it is fermented soy sauce since Kikkoman owns majority of the soy sauce market and their soy sauce is fermented.

      For more information, see my latest article on this topic on –

      I hope this information helps.


  10. Once having ingested gluten is there anything that can be done to shorten or negate any gluten reactions ?

    Thanks for your time

    1. Michael,

      Unfortunately, besides drinking plenty of water (no more than 1/2 ounce per pound of your body weight), it’s a wait-it-out journey. Drinking water flushes toxins out of the body. Because I am not a medical professional, I verified this with a registered dietitian, who is highly respected in the gluten-free field, author Shelley Case.

      I wish a speedy recovery.


  11. I am not sure I understand. Does this mean that the wheat or barley in soy sauce does not have to be listed? So far, I have often gone by the product label, and, if it did not display any gluten ingredients, I bought the sauce. If this is really the case, it is time that the FDA to finally comes up with a better labeling policy, as I never had this issue in Europe, where both wheat and barley have to be labeled by law.

    1. Hi Lollorosso,

      I neglected to add the word “not” where it should have been, “…likely that you will not have a gluten reaction.” The soy sauces tested were not gluten-free soy sauce. They were the regular soy sauce that contained gluten. Because majority of them tested below 20 ppm, it is unlikely that anyone would have a reaction. The study did show however, that some people with gluten intolerance did have a reaction to the these soy sauces, though. We’ll never know the true reason, though.

      I hope this clears things up.


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