In 1980, researchers in England reported a series of women with no evidence of celiac disease (the autoimmune disorder associated with gluten intolerance), who nevertheless resolved their chronic diarrhea on a gluten-free diet. The medical profession was skeptical at the time that non-celiac gluten sensitivity existed, and even 30 years later, such patients were commonly referred to psychiatrists. Psychological testing of such patients, however, found no evidence that they were suffering from any kind of psychosomatic hysteria.
The medical profession has a history of dismissing diseases as all in people’s heads—post-traumatic stress disorder, ulcerative colitis, migraines, ulcers, asthma, Parkinson’s disease, and multiple sclerosis. Despite resistance from the prevailing medical community at the time, these health problems have subsequently been confirmed to be credible physiologically-based disorders rather than psychologically-based confabulations.
On the flip side, the internet is rife with unsubstantiated claims about gluten free diets, which have spilled over into the popular press to make gluten the diet villain du jour, with claims like “17 million Americans are gluten sensitive.” However, it must be remembered that the gluten-free food industry is a big business. When literally billions are at stake, it’s hard to trust anybody. As always, it’s best to stick to the science.
What sort of evidence do we have for the existence of a condition presumed to be so widespread? Not much. The evidence base for such claims has been unfortunately very thin because we haven’t had randomized controlled trials demonstrating that the entity even exists. The gold-standard for confirming non-celiac gluten sensitivity requires a gluten-free diet, followed by a double-blind, randomized, placebo-controlled food challenge. For example, give people a muffin and don’t tell them if it’s gluten-free or gluten-filled—to control for placebo effects—and see what happens. The reason this is necessary is because when you actually do this, a number of quote-unquote “gluten-sensitive” patients don’t react at all to disguised gluten and instead react to the gluten-free placebo.
We never had that level of evidence until 2011, when a double-blind, randomized placebo-controlled trial was published, which tested to see if patients complaining of irritable bowel symptoms who claimed they felt better on a gluten free diet—despite not having celiac disease—actually could tell if they were given gluten containing bread and muffins or gluten-free bread and muffins.
Subjects started out gluten-free and symptom-free for two weeks and then were challenged with the bread and muffins. In my video, Is Gluten Sensitivity Real?, you can see what happened to the 15 patients who got the placebo, meaning they started out on a gluten-free diet and continued on a gluten-free diet. They got worse. Just the thought that they may be eating something that was bad for them made them feel crampy and bloated. This is what’s called the nocebo effect. The placebo effect is when you give someone something useless and they feel better; the nocebo effect is when you give someone something harmless and they feel worse. On the other hand, the small group that got the actual gluten, felt even worse still. The researchers concluded that non-celiac gluten intolerance may therefore indeed exist.
It was a small study, though, and even though the researchers claimed the gluten-free bread and muffins were indistinguishable, maybe at some level the patients could tell which was which. So, in 2012, researchers in Italy took 920 patients that had been diagnosed with non-celiac gluten sensitivity and put them to the test with a double-blinded wheat challenge by giving them capsules filled with wheat flour or filled with placebo powder. More than two-thirds failed the test, such as getting worse on the placebo or better on the wheat. But of those that passed, there was a clear benefit to staying on the wheat-free diet. The researchers concluded that their findings confirmed the existence of a non-celiac wheat sensitivity. Note I said “wheat sensitivity,” not “gluten sensitivity.”
Gluten itself may not be causing gut symptoms at all. Most people with wheat sensitivity have a variety of other food sensitivities. Two thirds are sensitive to cow’s milk protein, and many are sensitive to eggs. If we put people on a diet low in common triggers of irritable bowel symptoms, and then challenge them with gluten, there’s no effect. We find the same increase in symptoms with high gluten, low gluten, or no gluten diets, calling into question the very existence of non-celiac gluten sensitivity.
Interestingly, despite being informed that avoiding gluten didn’t seem to do a thing for their gut symptoms, many participants opted to continue following a gluten-free diet as they subjectively described “feeling better.” So, researchers wondered if avoiding gluten might improve the mood of those with wheat sensitivity. Indeed, short-term exposure to gluten appeared to induce feelings of depression in these patients. Whether non-celiac gluten sensitivity is a disease of the mind or the gut, it is no longer a condition that can be dismissed.
More than 10,000 articles have been published on gluten in medical journals—intimidating even for me! Combined with the multi-billion dollar financial interests on both sides, it makes for a difficult task. But I think I did it! This is the first of a 3-part series summarizing the best available science on gluten. Also check out: Gluten-Free Diets: Separating the Wheat from the Chat and How to Diagnose Gluten Intolerance.
Why this apparent increase in food sensitivities in recent decades? It could be because of pollutant exposure (see Alkylphenol Endocrine Disruptors and Allergies and Dietary Sources of Alkylphenol Endocrine Disruptors).
What can we do about preventing so-called atopic diseases (like allergies, asthma, and eczema)? See my videos Preventing Allergies in Adulthood and Preventing Allergies in Childhood. The weirdest example of an emerging food sensitivity may be the tick-bite related meat allergy story I review in Alpha Gal and the Lone Star Tick and Tick Bites, Meat Allergies, and Chronic Urticaria.
Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.
Image Credit: Guillaume Paumier / Flickr