Gluten-Free Diets: The Nocebo Effect

Gluten-free Singles

Gluten-free Singles

I recently noticed my bottle of Ca-Mg-Zn (calcium-Magnesium-Zinc) tablets has a large “GLUTEN-FREE” on the label. This seems odd since I wouldn’t expect a lot of gluten in a tablet! Just as cereals once sported “Cholesterol Free!” labels, manufacturers have discovered some consumers will react positively to a label associated with healthy eating even when the food in question never contained any of the supposedly hazardous substance.

Celiac disease is a serious digestive disorder where even small amounts of gliaden (a component of gluten protein found in grains like wheat, barley, and rye) causes an auto-immune inflammation of the bowel, leading to malabsorption of nutrients, chronic constipation or diarrhea, and discomfort and low energy.

Less than 1% of the population suffers from true celiac disease. A larger group seems to have problems digesting wheat and other grain products, often called non-celiac gluten sensitivity, but this diagnosis has never been well proven, and recent studies show the digestive difficulties of these people are not due to gluten as such, but to other components of wheat and grains.

So like many memes, the “gluten-free diet” meme started from a truth: people with celiac disease suffer greatly if they consume anything with gluten. Added on was another truth: a larger group has some sensitivities to wheat and other grains. But then it became a runaway train of half-truths and marketing, where manufacturers discovered they could charge more and sell more by offering gluten-free products to meet demand mostly from those who had no real reason to avoid gluten.

From Canadian magazine MacLean’s:

Gluten-free products are a $90-million enterprise in Canada alone, and the sector is expected to grow at least 10 per cent each year through to 2018—an astounding feat for what is primarily a food-based category. In the United States, the market is valued at $4.2 billion and climbing. A landmark study by researchers at Dalhousie University in Halifax, published in the Canadian Journal of Dietetic Practice and Research in 2008, revealed that gluten-free foods were, on average, 242 per cent more expensive than their “regular” counterparts, and up to 455 per cent pricier in some cases. “If I was to manufacture a product,” says Dron, “there is no way that I would not have a gluten-free option in today’s day and age.”

With all these products, one might assume the need for gluten-free items is epidemic in Canada, that without them a public health crisis could emerge. In reality, the explanation for the recent explosion in demand is a spectacular mix of real medical concerns, changing views on what accounts for a healthy diet, savvy marketing and celebrity influence. Sports stars Steve Nash and Novak Djokovic insist going gluten-free has turned them into the finest and leanest athletes in the world. Public health messages have shifted focus from low fat and sugar-free to low-carb, partly to stave off rampant obesity. And the best-selling book Wheat Belly, by American cardiologist William Davis, published in 2011, has convinced millions to stop eating, as the author puts it, “a perfectly crafted Frankengrain” that “has exerted more harm than any foreign terrorist group can inflict on us.”

Note that it is easy to avoid gluten by not eating breads and cereals, and that changing your diet this way based on a false belief gluten harms you does, in fact, help most people lose weight — but because of the reduced carb consumption, not the lack of gluten.

Science Daily reports on a University of Florida study on popular beliefs about gluten-free foods:

Unlike their conventional counterparts, refined gluten-free foods, for the most part, are not enriched or fortified with essential vitamins and minerals. “If I’m a college student, and I want to lose weight, and I read on the Internet that a gluten-free diet is the way to go, I may start avoiding products that contain essential nutrients such as those found in cereal grains fortified with folic acid,” Shelnutt said. “The problem is you have a lot of healthy women who choose a gluten-free diet because they believe it is healthier for them and can help them lose weight and give them healthier skin.”

One of Shelnutt’s doctoral students, Caroline Dunn, wanted to know if gluten-free labeling has any impact on how consumers perceive the foods’ taste and nutrition. In a one-day experiment on the UF campus in Gainesville in February, 97 people ate cookies and chips, all gluten-free. Half were labeled “gluten-free”; the other half labeled “conventional.”

Participants then rated each food on a nine-point scale for how much they liked the flavor and texture. They also filled out a questionnaire, said Shelnutt, a faculty member with UF’s Institute of Food and Agricultural Sciences.

About a third of participants said they believed gluten-free foods to be healthier than those labeled “conventional,” a figure she thought would be much lower. While avoiding gluten-containing foods can reduce carbohydrate intake, thus helping some lose weight, many health experts say a gluten-free diet is no healthier than a conventional diet except for those with celiac disease.

Paying high prices for gluten-free products is necessary for celiac sufferers, and the gluten-free diet fad has improved their access to gluten-free foods a great deal — which is good. But for the vast majority, it is simply superstition and pseudoscience; while it probably is a good idea for most people to eat less bread and grains (and starches and sweets!), there is no reason to pay high prices for special gluten-free foods.

A nice wrapup in Forbes on the careful scientific experiments showing the apparent nonexistence of non-celiac gluten sensitivity:

In 2011, Peter Gibson, a professor of gastroenterology at Monash University and director of the GI Unit at The Alfred Hospital in Melbourne, Australia, published a study that found gluten, a protein found in grains like wheat, rye, and barley, to cause gastrointestinal distress in patients without celiac disease, an autoimmune disorder unequivocally triggered by gluten. Double-blinded, randomized, and placebo-controlled, the experiment was one of the strongest pieces of evidence to date that non-celiac gluten sensitivity (NCGS), more commonly known as gluten intolerance, is a genuine condition.

By extension, the study also lent credibility to the meteoric rise of the gluten-free diet. Surveys now show that 30% of Americans would like to eat less gluten, and sales of gluten-free products are estimated to hit $15 billion by 2016 — that’s a 50% jump over 2013′s numbers!

But like any meticulous scientist, Gibson wasn’t satisfied with his first study. His research turned up no clues to what actually might be causing subjects’ adverse reactions to gluten. Moreover, there were many more variables to control! What if some hidden confounder was mucking up the results? He resolved to repeat the trial with a level of rigor lacking in most nutritional research. Subjects would be provided with every single meal for the duration of the trial. Any and all potential dietary triggers for gastrointestinal symptoms would be removed, including lactose (from milk products), certain preservatives like benzoates, propionate, sulfites, and nitrites, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs. And last, but not least, nine days worth of urine and fecal matter would be collected. With this new study, Gibson wasn’t messing around.

37 subjects took part, all confirmed not to have celiac disease but whose gastrointestinal symptoms improved on a gluten-free diet, thus fulfilling the diagnostic criteria for non-celiac gluten sensitivity.** They were first fed a diet low in FODMAPs for two weeks (baseline), then were given one of three diets for a week with either 16 grams per day of added gluten (high-gluten), 2 grams of gluten and 14 grams of whey protein isolate (low-gluten), or 16 grams of whey protein isolate (placebo). Each subject shuffled through every single diet so that they could serve as their own controls, and none ever knew what specific diet he or she was eating. After the main experiment, a second was conducted to ensure that the whey protein placebo was suitable. In this one, 22 of the original subjects shuffled through three different diets — 16 grams of added gluten, 16 grams of added whey protein isolate, or the baseline diet — for three days each.

Analyzing the data, Gibson found that each treatment diet, whether it included gluten or not, prompted subjects to report a worsening of gastrointestinal symptoms to similar degrees. Reported pain, bloating, nausea, and gas all increased over the baseline low-FODMAP diet. Even in the second experiment, when the placebo diet was identical to the baseline diet, subjects reported a worsening of symptoms! The data clearly indicated that a nocebo effect, the same reaction that prompts some people to get sick from wind turbines and wireless signals, was at work here. Patients reported gastrointestinal distress without any apparent physical cause. Gluten wasn’t the culprit; the cause was likely psychological. Participants expected the diets to make them sick, and so they did. The finding led Gibson to the opposite conclusion of his 2011 research:

“In contrast to our first study… we could find absolutely no specific response to gluten.”

Instead, as RCS reported last week, FODMAPS are a far more likely cause of the gastrointestinal problems attributed to gluten intolerance. Jessica Biesiekierski, a gastroenterologist formerly at Monash University and now based out of the Translational Research Center for Gastrointestinal Disorders at the University of Leuven in Belgium,* and lead author of the study alongside Gibson, noted that when participants consumed the baseline low-FODMAP diet, almost all reported that their symptoms improved!

“Reduction of FODMAPs in their diets uniformly reduced gastrointestinal symptoms and fatigue in the run-in period, after which they were minimally symptomatic.”

Coincidentally, some of the largest dietary sources of FODMAPs — specifically bread products — are removed when adopting a gluten-free diet, which could explain why the millions of people worldwide who swear by gluten-free diets feel better after going gluten-free.

For more on diet and weight loss:

Getting to Less Than 10% Body Fat Like the Models – Ask Me How!
Starbucks, Jamba Juice Make You Fat
Fat Doesn’t Make You Fat. Government Guidelines Did!
‘Fed Up’ Asks, Are All Calories Equal?
Fructose: The True Villain?
More on “Fed Up”, Sugar Subsidies, and Obesity
Another Study on Diet Drinks
LeBron James Cut Carbs for Lean Look
Why We’re Fat: In-Depth Studies Under Way
Almonds: Superfood, Eat Them Daily for Heart Health
Fish Oil Supplements Ward Off Dementia
More on Diet Drinks: Best Studies Show They Aid Weight Loss
Vani Hari: “Food Babe” and Quack
Cleanses and Detox Diets: Quackery
Sugared Soft Drinks: Health Risk? (and What About Diet Soda?)
Gluten-Free Diets: The Nocebo Effect
Acidic Soft Drinks and Sodas: Demineralization Damages Teeth
Fish and Fish Oil for Better Brain Health
Salt: New Research Says Too Little May Be Unhealthy
Bulletproof Coffee: Coffee, Oil, and Butter for Breakfast?

For more on useful supplements and life-extending habits:

Low-Dose Aspirin Reduces Pancreatic Cancer
Daily Aspirin Regimen Reduces Cancer Rates
Lower Back Pain: Acetaminophen (Tylenol, Paracetamol) Useless
Scams: Multi-Level Marketing, Herbalife
Vitamin D: Anti-Dementia?


  1. No one in his right mind would eliminate wheat from his diet for naught. I personally hated even considering it. I suffered many years of pain and ill-health never thinking it was due to any food. I removed wheat for five days and EVERY symptom disappeared. If you ever try to eliminate wheat from your diet, you won’t think anyone would do it for long without a good reason. Eliminating wheat messes up your enjoyment of life. I have adapted, but it has not been easy. If you think over what it really means to quit wheat, I think you will realize no one wants to do it.

    1. I do love bread, and pancakes, and cereal! But I have cut way back, not because wheat causes digestive problems for me, but because a diet very low in carbs seems to help in several dimensions — fitness, lower body fat, energy levels. Small portions are a way to continue to enjoy bread and pasta, for those who are not truly wheat-sensitive. Bread is kind of the original processed food — invented and refined after most of our evolution.

      I console myself with delicious foods like avocados, walnuts, almonds, olive oil, salmon, vegetables, and occasionally quinoa for that side dish. I don’t feel all that deprived, though eating out can be a challenge.

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