Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

A Glut of Gluten

We hear a lot about gluten sensitivity. Today we go deep to understand better ways to control that sensitivity and improve our diet.

This episode features audio from How to Diagnose Gluten Intolerance, Is Gluten Sensitivity Real?, and Gluten-Free Diets: Separating the Wheat from the Chat. Visit the video pages for all sources and doctor’s notes related to this podcast.


Hello and welcome to the Nutrition Facts podcast.  I’m your host, Dr. Michael Greger. 

Now, I know I’m known for explaining how not to do certain things (just look at my books, How Not to Die, the one I’m working on right now–How Not to Diet), but what I actually have to share with you is quite positive and boils down to this: What’s the best way to live a healthy life?  Here are some answers.

Today, we’re going to get sensitive – with gluten – and try to understand why some people react to it.  Symptoms of celiac disease (an immune reaction to the gluten protein in wheat, barley, and rye) can include irritable bowel type symptoms such as bloating and abdominal pain, but now we realize that there are people who don’t have celiac but still may be gluten sensitive. 

After a formal evaluation to rule out celiac disease, those who suspect they might be gluten sensitive should first try improving their diet and then have other causes excluded before going on a gluten-free diet, since as many as 1 in 3 people who avoid gluten for symptom control end up having a different disease altogether.

Symptoms of gluten sensitivity include irritable bowel type symptoms such as bloating, abdominal pain, and changes in bowel habits, as well as systemic manifestations such as brain fog, headache, fatigue, depression, joint and muscle aches, numbness in the extremities, a skin rash or anemia. If those who suspect they might be gluten sensitive should not go on a gluten-free diet, what should they do?

The first thing is a formal evaluation for celiac disease, which currently involves blood tests and a small intestinal biopsy. If that’s positive, then one goes on a gluten-free diet, but if it’s negative we should try eating a healthier diet, more fruits and vegetables, more whole grains and beans while avoiding processed junk.

See, in the past, a gluten-free diet had many benefits over the traditional American diet because it required increasing fruit and vegetable intake, so no wonder people felt better eating gluten free—no more deep-fried Twinkies, couldn’t eat in fast food restaurants. Now, though, there is just as much gluten-free junk out there.  I call it the vegan doughnut phenomenon. A few decades ago vegans were forced to eat healthy, eat actual vegetables, but now they can eat their cheesy puffs, while waiting for their candy-coated chocolate marshmallows to deep-fry in vegan bacon grease.

If a healthy diet doesn’t help, then I might add another step here, and that is try to rule out other causes of chronic intestinal distress. When researchers study PWAWGs (that’s what they’re called in the literature), people who avoid wheat and/or gluten. In a study of 84 PWAWGs, about a third didn’t appear to have gluten sensitivity at all, but instead an overgrowth of bacteria in their small intestine, or were fructose or lactose intolerant, or had a neuromuscular disorder like gastroparesis or pelvic floor dysfunction. When those are all ruled out as well, then I’d suggest people suffering from chronic suspicious symptoms try a gluten-free diet, and if symptoms improve, stick with it, though maybe re-challenging with gluten periodically.

Unlike celiac disease, a gluten-free diet is begun not to prevent serious complications from an autoimmune reaction, but just to resolve gluten sensitivity symptoms to try to improve patients’ quality of life. However, a gluten-free diet itself can reduce quality of life, so it’s a matter of trying to continually strike the balance. For example, gluten-free foods can be expensive, averaging about triple the cost and so most people would benefit more from buying an extra bunch of kale or blueberries instead.

No current data suggest that that general population should maintain a gluten-free lifestyle, but for those with a celiac disease, wheat allergy, or sensitivity diagnosis, gluten-free diets can be a life-saver.

For more than 30 years, the medical profession has debated the existence of an intolerance to gluten, unrelated to wheat allergy or celiac disease. Let’s review the evidence, pro and con.

In 1980, researchers in England reported a series of women who suffered from chronic diarrhea that resolved on a gluten-free diet, yet did not have evidence of celiac disease, the autoimmune disorder associated with gluten intolerance. The medical profession was skeptical at the time, and even 30 years later, so much so, that much like patients who had irritable bowel syndrome, patients claiming non-celiac gluten sensitivity were commonly referred to psychiatrists because they were believed to have an underlying mental illness. Psychological testing of such patients, however, found no evidence that they were suffering from some kind of psychosomatic hysteria.

The medical profession has a history of dismissing diseases as all in people’s heads—PTSD, ulcerative colitis, migraines, ulcers, asthma, Parkinson’s, MS. 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 flipside, the internet is rife with unsubstantiated claims about gluten-free diets, which has 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 this is also “big business.”

When literally billions of dollars are at stake, it’s hard to trust anybody; so, as always, 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 was unfortunately very thin because we didn’t have 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. Like, you give someone a muffin and they’re not told if it’s a gluten-free muffin or gluten-filled muffin—to control for placebo effects—and see what happens. The reason this is necessary is because when you actually do this, a number of “gluten-sensitive” patients don’t react at all to disguised gluten and instead react to the gluten-free placebo. So it was truly was “in their heads.”

But 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 type symptoms who claimed they felt better on a gluten-free diet—despite not having celiac disease—actually could tell if they were given gluten-free bread and muffins or gluten-containing bread and muffins.  They started out gluten-free and symptom-free for two weeks and then they were challenged with the bread and muffins. Here’s 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 all crampy and bloated. This is what’s called a 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. But the small group that got the actual gluten, felt worse still. So, they concluded, this non-celiac gluten intolerance may actually exist.

It was a small study, though, and even though they claimed the gluten-free bread and muffins were indistinguishable, maybe at some level the patients could tell which is 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 not bread and muffins, but capsules filled with wheat flour or filled with placebo flour—or kind of placebo powder, no flour at all. And more than two-thirds failed the test, like they got 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, confirming the existence of a non-celiac wheat sensitivity. Now, note they said wheat sensitivity, not gluten sensitivity.

Gluten itself may not be causing gut symptoms at all. See, most people with wheat sensitivity have a variety of other food sensitivities. Two-thirds are sensitive to cow’s milk protein as well, then eggs were the most common culprit after that.

So, if you put people on a diet low in common triggers of irritable bowel symptoms and then challenge them with gluten, there’s no effect. Same increase in symptoms with high gluten, low gluten or no gluten, calling into question the very existence of non-celiac gluten sensitivity.

Interestingly, despite being informed that avoiding gluten wasn’t apparently doing a thing for their gut symptoms, many participants opted to continue following a gluten-free diet, as they just subjectively described “feeling better,” so the researchers wondered if avoiding gluten might be improving the mood of those with wheat sensitivity.  And, indeed, short-term exposure to gluten appeared to induce feelings of depression in these patients. But whether non-celiac gluten sensitivity is a disease of the mind or the gut, it is no longer a condition that can be dismissed.

How common is gluten sensitivity? Are there benefits to gluten? Why does the medical profession explicitly advise against people who suspect they might be gluten intolerant from just going on a gluten-free diet?

Until only a few years ago, almost the whole of the scientific world maintained that the wheat protein gluten would provoke negative effects only in people with rare conditions such as celiac disease or wheat allergies, but by the early part of 2013, it was largely becoming accepted that some non-celiac patients could suffer from gluten or wheat sensitivity

And indeed a consensus panel of experts now officially recognizes three gluten-related conditions: wheat allergy, celiac disease, and gluten sensitivity. So what percent of the population should avoid wheat?

Well, about one in a thousand may have a wheat allergy, nearly 1 in a 100 may have celiac disease, and it appears to be on the rise, though there’s still less than about a 1 in 10,000 chance Americans will get diagnosed with celiac in any given year. How common is wheat or gluten sensitivity? Our best estimate at this point is that in that same kind of general range, slightly higher than 1%, but still that’s potentially millions of people who may have been suffering for years who could have been cured by simple dietary means, yet went unrecognized and un-helped by the medical profession.

Although gluten sensitivity continues to gain medical credibility, we still don’t know how it works, or how much gluten can be tolerated, if it’s reversible or not and what the long-term complications might be of not sticking to the diet. Considering the lack of knowledge, maybe people with gluten sensitivity should be trying to reintroduce gluten back into their diet every year or so to see if it’s still causing problems.

The reason health professionals don’t want to see people on gluten-free diets unless absolutely necessary is that for the 98% of people that don’t have gluten issues, whole grains—including the gluten grains wheat, barley and rye—are health promoting, linked to the reduced risk of coronary heart disease, cancer, diabetes, obesity and other chronic diseases.

Just like because some people have a peanut allergy, doesn’t mean that everyone should avoid peanuts. There is no evidence to suggest that following a gluten-free diet has any significant benefits in the general population. Indeed, there is some evidence to suggest that a gluten-free diet may adversely affect gut health in those without celiac disease or gluten sensitivity or allergy. A month on a gluten-free diet may hurt our gut flora and immune function, potentially setting those on gluten-free diets up for an overgrowth of harmful bacteria in their intestines. Why? Because, ironically, of the beneficial effects of the very components wheat sensitive people have problems with—like the FODMAP fructans that act as prebiotics and feed our good bacteria, or the gluten itself, which may boost immune function. Less than a week of added gluten protein significantly increases natural killer cell activity, which could be expected to improve our body’s ability to fight cancer and viral infections. High-gluten bread improves triglyceride levels better than regular gluten bread, as another example.

Ironically, one of the greatest threats gluten-free diets may be the gluten itself. Self-prescription of a gluten-free diet may undermine our ability to pick up celiac disease, the much more serious form of gluten intolerance. The way we diagnose celiac is by looking for the inflammation caused by gluten in celiac sufferers, but if they haven’t been eating a lot of gluten, we might miss the disease.  Hence, rather than being on a gluten-free diet, we want celiac suspects to be on a gluten-loaded diet. We’re talkin’ 4-6 slices of gluten-packed bread a day every day for at least a month so we can definitively diagnose the disease.

Why does it matter so much to get a formal diagnosis if you’re already on a gluten-free diet? Well, it’s a genetic disease so you’ll know to test the family, but most importantly many people on gluten-free diets are not actually on gluten-free diets. Even 20 parts per million can be toxic to someone with celiac. Many on so-called gluten-free diets inadvertently still eat gluten. Sometimes there’s contamination of gluten-free products, so even foods labeled “gluten-free” may still not be safe for celiac sufferers. That’s why we need to know.

The irony, editorialized in a prominent medical journal, of many celiac patients not knowing their diagnosis, while millions of non-sufferers banish gluten from their diets, can be considered a public health farce.

To see any graphs, charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page.  There, you’ll find all the detailed information you need – plus links to all the sources we cite for each of these topics.

Be sure to check out my new How Not to Die Cookbook.  It’s beautifully designed, with more than 120 recipes for delicious, plant-based meals, snacks and beverages.  All the proceeds from the sales of all my books all go to charity.  I just want you to be healthier.  

NutritionFacts.org is a nonprofit, science-based public service, where you can sign up for free daily updates on the latest in nutrition research via bite-sized videos and articles.

Everything on the website is free. There’s no ads, no corporate sponsorship.  It’s strictly non-commercial.  I’m not selling anything. I just put it up as a public service, as a labor of love – as a tribute to my grandmother – whose own life was saved with evidence-based nutrition.

Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.

This is just an approximation of the audio content, contributed by Allyson Burnett.


13 responses to “A Glut of Gluten

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  1. What I want to know – once and for all – is should people with Hashimotos disease avoid gluten? So many doctors say this but the info is conflicting and inconsistent. Is there ANY proof that his ramps up the attack on the thyroid and perpetuates the condition? I’d really like Dr Greger to weigh in on this, PLEASE!

    1. Hi Andi – I’m Janelle, a Health Support Volunteer for Dr. Greger and a Registered Dietitian. Thanks for your question! It is only clinically necessary for those with Celiac disease to avoid gluten. It is not proven that any other condition requires a gluten-free diet.

      To note: since Hashimoto’s disease is an autoimmune disease, it is associated with other autoimmune diseases, such as Celiac disease. Now this does not mean that if you have Hashimoto’s you automatically have Celiac disease. In order to determine if you have Celiac disease, the #1 thing to do is see your doctor and to have a blood test and intestinal biopsy done. If you test positive, THEN it is recommended to follow a gluten-free diet indefinitely. If you test negative, the best thing to do is focus on a general, healthy diet based on whole, plant foods. I hope this clears up any confusion!

  2. My FODMAP friend contacted me today and said that her body is healing and she was able to eat a hamburger bun without getting sick.

    A few weeks ago, we went out and she ate the white rice, which came with my meal. The first white rice she had in a long time.

    Your videos on the subject suggest to me that she is in the 2/3rds who didn’t really have it category.

    Wondering what she had, which made her sick for 40 years.

    Apparently not gluten sensitivity OR her gut microbiome got healed or something.

  3. And also: people should get tested for celiac disease before going on a gluten-free diet, because if they are gluten/wheat sensitive, they will likely become much more sensitive to gluten once they’re on a gf diet, and the reaction will be much worse when they’re exposed. Doing a gluten challenge in order to get tested for celiac disease – eating several slices of bread a day – becomes an awful thing to contemplate, once you’re so sensitive that eating a tiny crumb accidentally will make you sick for days.
    There was a paper in 2016 that made progress in figuring out a mechanism for non-celiac wheat sensitivity. That was “Intestinal cell damage and systemic immune activation in individuals reporting sensitivity to wheat in the absence of coeliac disease”, by Uhde et all in the journal “Gut”. This paper is available free online at https://gut.bmj.com/content/65/12/1930
    It seems like what was happening was that for some reason, there was epithelial cell damage in the gut that resulted in microbial cell products such as lipopolysaccharide getting into the blood and causing immune activation. So there might be two separate immune responses: one in the gut to wheat that causes the epithelial cell damage, and then later, a systemic immune response to the bacterial products that end up in the bloodstream.

  4. Laura,

    Totally agree with you that if celiac/sensitivity is the potential diagnosis it should trigger testing, with an extensive panel. Typically it’s unnecessary and unwise to subject someone to loading with lots of allergens, prior to a test, especially if their aware of some reactions, be that moderate to severe.

    You correct in terms of the hypersensitive nature of removal of an allergen however, one should never load test with “several slices of bread”. The typical challenge should be a very small amount of the questionable product, and I mean a very small amount. This challenge would be followed by an increasing amount….assuming no reaction.

    Typically we would ask a patient choosing the elimination/provocation approach to monitor their pulse rate at different times along with subjectively asking how they feel and keeping track, and avoiding a second challenge should reactions be clearly seen. The process takes place over a three day period, with a washout of no allergens the 3 day, again assuming no reactions.

    Epithelial integrity and immune hyper-activation can be accessed via lab testing. There are a number of mechanism and chemical indications that would typically be part of a medical workup for gluten sensitivity.

    I’d like to return to your original statement that if you know a small amount of gluten containing food is going to set in motion clear reactions, why would you even go through the expensive and time consuming testing ? My assessment/treatment plan of an patient who has this clear reaction, and it’s not due to other substances is to address the underlying damage done to the GI tract and remain vigilant that no gluten containing substances are ingested.

    1. Dr. Kadish, I was talking about the blood tests / biopsy that are done to diagnose celiac disease.
      As Dr. Greger says in the video, “we want celiac suspects to be on a gluten-loaded diet. We’re talkin’ 4-6 slices of gluten-packed bread a day every day for at least a month so we can definitively diagnose the disease.”.
      If someone has celiac disease, eating 4-6 slices of bread for a month is likely to re-create the intestinal damage that’s typical of celiac disease. Then, celiac blood tests or biopsy are done, and they will be positive for CD.

    2. Drkadish, Dr. Greger’s answer to your question “why test for celiac disease if you have severe reactions” is towards the end of the transcript.
      Another reason to want to know if you actually have celiac disease is that CD has been extensively studied, correlated with other autoimmune diseases etc. A doctor (MD or DO) can do more to help if they know whether someone has CD or not.

      1. Hello, thanks a lot for your comment!

        There’re different mechanisms involved in the pathogenesis of gluten-related disorders. We have for example celiac disease and wheat allergy, which might involve in both cases an autoimmune and allergic process, mediated by the different type of cells and antibodies like Immunoglobulin E (IgE). In cases of celiac disease might be as well a genetic predisposition and the association with other autoimmune disorders.

        Gluten sensitivity, on the other hand, is characterized by a wide range of intestinal and extra-intestinal symptoms arising shortly after the ingestion of gluten-containing food, gluten sensitivity is not still that well understood, but scientists believe that there is a non-autoimmune non-allergic process.


        And by your second question, of course, gut microbiota changes over time! But it’s not just by magic, there’re a lot of factors that are involved in gut microbiota health, such as antibiotic treatment, animal-based diet, age, bowel dysfunction, type 2 diabetes, and obesity, there are even a few studies that link not being physically active with gut dysbiosis.



        For more info check the collection of microbiota videos by Dr. Greger >> https://nutritionfacts.org/topics/microbiome/

        1. From “Non-Celiac Wheat Sensitivity Diagnosed by Double-Blind Placebo-Controlled Challenge: Exploring a New Clinical Entity” by Carroccio et al:

          “Two hundred and seventy-six patients with wheat sensitivity (WS), as diagnosed by DBPC challenge, were included. Two groups showing distinct clinical characteristics were identified: WS alone (group 1) and WS associated with multiple food hypersensitivity (group 2). As a whole group, the WS patients showed a higher frequency of anemia, weight loss, self-reported wheat intolerance, coexistent atopy, and food allergy in infancy than the IBS controls. There was also a higher frequency of positive serum assays for IgG/IgA anti-gliadin and cytometric basophil activation in “in vitro” assay. The main histology characteristic of WS patients was eosinophil infiltration of the duodenal and colon mucosa. Patients with WS alone were characterized by clinical features very similar to those found in CD patients. Patients with multiple food sensitivity were characterized by clinical features similar to those found in allergic patients.”

          Dr. Carroccio also wrote a 2014 review article “Non-celiac gluten sensitivity: literature review” https://www.ncbi.nlm.nih.gov/pubmed/24533607 which goes into detail about different immune and non-immune responses to wheat.

  5. Dr Fasano showed how Gliadin in gluten triggers the production of the protein called zonulin. This breaks down the gut lining causing leaky gut. This in turn causes inflamation. Most autoimmune disease sufferers were shown to have high zonulin and leaky gut. In Physiol. Rev. 91, no 1 (Jan. 2011). I came across this info in The Grain Brain Whole Life Plan by Dr Perlmutter.

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