Note: Since I wrote this in 2011, medical researchers have uncovered some evidence for potential cross-reactivity in corn. Read more here: Study Finds Some Evidence for Corn Cross-Reactivity in Celiac Disease.
Ever hear of the concept "cross-reactivity"? I hadn't until recently, when I started to see references to it on the various celiac disease boards I follow. According to the theory of "cross-reactivity," certain foods (including grains, dairy and processed foods such as chocolate) supposedly "mimic" gluten in your body, causing a glutening when you haven't consumed any gluten.
Just as this concept is getting more press, certain vendors are heavily promoting tests that purport to tell you whether your body is mistaking other substances (such as other grains) for gluten, and reacting accordingly.
Well, I've looked into this -- including into the medical references being used to back up the concept -- and I have to tell you that there's no strong scientific/medical backing for "cross-reactivity."
Yes, it sounds somewhat plausible ... it seemingly could explain why so many of us react to foods even though they're labeled "gluten-free." And I can relate to being frustrated because you're following the gluten-free diet very strictly but still having frequent reactions.
However, in my experience those who fail to heal on a gluten-free diet are not seeing "cross-reactivity" from other foods, nor do they have multiple "additional intolerances" to foods other than gluten. That's despite the fact that both these concepts are commonly discussed and endorsed on various celiac forums, and some medical practitioners are promoting them.
Instead, in my experience, those who are still suffering with celiac symptoms despite a "gluten-free" diet invariably are getting glutened by the tiny amounts of gluten in their "gluten-free" foods.
You may know that the term "gluten-free" has no legal meaning at the moment -- the FDA has proposed a definition, but has not finalized it (see my article on Gluten-Free Food Label Rules for more details).
Many of the gluten-free-labeled foods we see on grocery store shelves contain a tiny bit of gluten. Just as something can be labeled "fat-free" if it contains less than 0.5 g of fat per serving (it's not truly fat-free, it simply meets the legal definition for "fat-free"), something can be labeled "gluten-free" even if it contains some gluten.
Most manufacturers do keep their gluten-free labeled products below the proposed FDA standard of 20 parts per million of gluten, and many keep them below 10 parts per million. Both 20 ppm and 10 ppm are very small amounts of gluten, of course.
However, those small amounts of gluten are still more than enough to cause reactions in the very sensitive among us (and I'm one of these super-sensitives -- I react to far less than even 10 ppm). See my article on Glutened While Eating Gluten-Free, plus my blog post "Is It A Real Reaction? Or Is It All In Your Head?", for more information on this.
Sadly, many grains and many other ingredients common in processed foods such as chocolate frequently are contaminated with gluten. Most of these test below that proposed FDA standard of 20 parts per million ... but that doesn't help you if you react to less than 20 parts per million of gluten in your food. I've had to cut out almost all grains and almost all processed foods to reduce the level of gluten in my diet to a point where I feel perfectly healthy again.
Before you buy into the concept of "cross-reactive foods" or "additional intolerances," make sure you try the foods you suspect in their purest forms possible.
For example, if you seem to react to corn, buy some unhusked corn on the cob and husk and cook it yourself. If you think your problem is soy (which is almost always badly cross-contaminated with gluten due to the fact that it's grown in rotation with wheat), grow some organic edamame of your own and try it. If you seem to react to chocolate, buy some raw cacao beans, wash, roast and shell them yourself, and determine if you react to those.
If you don't react to these foods in their natural states, then your problem almost certainly is trace gluten.
It takes plenty of work to figure this out (especially if you're not in a position to grow your own foods!), but you'll eventually determine whether your problem is those foods, or whether it's gluten introduced somewhere in the food chain. Again, in my experience, the problem is almost always gluten.
It makes far more sense to me that those who continue to have gluten symptoms are reacting to the gluten in their diets, even though that gluten is at a very low level, than to other foods our bodies are mistaking for gluten -- especially since the molecular structure of these supposedly cross-reactive foods is completely different from gluten.
Your body knows the difference between gluten and other types of foods, and it knows when you've gotten that poisonous substance ... even if the package is labeled "gluten-free."