Mushrooms - are they safe for celiacs?

[TheDHhurts]

I stopped eating mushrooms post-diagnosis because I was told they were grown on hay/barley/some sort of glutenous substance, and that I would end up getting cross-contaminated.

More recently I've seen some people challenge this, saying that modern farming practices do not expose mushrooms to gluten cross-contamination.

I'd like to try mushrooms again, but I'm very cautious about introducing new foods because I'm very sensitive (I have DH, and seem to break out from minute amounts of cross-contamination). Any suggestions on how I should proceed here?

Thanks!

[Blue-Sky]

I eat mushrooms often and I don't get a reaction. I doubt that mushrooms are grown on wheat as it is well known that a lot of people are allergic to wheat. If a product contains wheat intentionally it has to be labelled. This probably makes it less likely for companies to take risks with peoples healths by using wheat. Probably the same for barely as it is not safe for Celiacs. This source says they are grown on millet. Hay is gluten free. 

https://farmingbase.com/growing-vegetables-in-greenhouses-is-more-profitable/

Also mushrooms get washed really well and I don't think they absorb nutrients from the soil but they probably wouldn't absorb the wheat itself.

[Scott Adams]

I've never heard that mushrooms could contain any gluten, even if they were grown on wheat and/or barley. If you simply wash them before use they should be gluten-free. This sounds like a similar version of an age-old myth that strawberries could contain gluten because they might use wheat straw under the plants. I don't believe that either claim would hold up to serious scrutiny. 

[Celiacmanbill]

the magic ones are often not grown on a gluten free grain but as for others I've only ever seen Maitake and one other type grown on a gluten grain

[Tannin]

I love mushrooms. I can tell you from a home cultivation point of reference that what is used to grow  the mycelium (building blocks of fungus) that eventually produces fungal colonies that make mushrooms varies wildly depending on the variety. I prefer raising varieties that don’t require rye berries or millet. However, that’s not always financially plausible- I just am careful with how I harvest and prepare those and haven’t had a contamination issue to my knowledge. I raise mushrooms  in sealed tubs far away from where I store and prepare food. Mushrooms themselves are primarily made of chitin. Chitin has zero gluten in it to my knowledge. The issue is contamination. If you find yourself paralyzed about potential contamination of commercial farm fresh mushrooms like Button or Portabella, you can actually peel the outer layers off of the caps and foot chopping off the bottom most portion of the foot. I personally get tested every year to see how my antibody levels are doing. I seem to be doing fine without basing my diet exclusively around food with official Gluten Free labeling. Where this matters most is *pre prepared foods*. Fresh mushrooms I prep myself no problem. If I were to buy prepared mushrooms, I’d scrutinize labels. In restaurants that’s a whole other ballgame. Hope this helps.  

[Scott Adams]

Hi @Tannin, in general mushrooms haven't been on the radar as a gluten threat, so I am not sure why you seem to be so concerned with commercial mushrooms like button or Portabella varieties? 

While I appreciate the detailed perspective from a cultivation standpoint, I think it's important to clarify that the core concern you're describing—substrate contamination—is an extremely niche risk for the vast majority of celiacs. For anyone buying standard commercial mushrooms like cremini or portobella from a grocery store, the mushroom itself is inherently and safely gluten-free; it's a fungus, not a grain. 

The real, practical risk of gluten exposure doesn't come from the remote chance of rye berry residue on a fresh mushroom cap, but from much more likely sources like pre-sliced packaging facilities, canned products with added flavorings, or restaurant preparation where shared equipment and sauces are the true culprits. Focusing on peeling mushrooms seems to address a theoretical problem rather than the actual ones, which are handled by simply buying whole, fresh mushrooms and preparing them in a clean environment. For most people with gluten sensitivity, this is a non-issue, and the warning might create unnecessary alarm about an otherwise safe and healthy whole food.