Gluten Intolerance or Gluten-anxiety? A New Study Suggests You Could Be Nocebo-ing Yourself into Digestive Issues
It's thought that around 12% of people have a food intolerance, while around 5% of the UK have a more severe food allergy. Cases of each are on the rise, leading to both concern over why so many more people are experiencing serious immune-system reactions to foods and eye-rolling over dinner tables when half the guests claim to have developed a lactose intolerance since you saw them gorging out over the cheese plate just a month ago.
Gluten in particular has been victim of the recent rise of elimination diets. While celiac disease is incredibly serious, it impacts only 1% of people - yet some studies show up to 30% of people eat a gluten-free diet due to non-celiac gluten sensitivity (NCGS).
NCGS is associated with abdominal pain or discomfort, bloating, altered stool patterns, tiredness and headaches - symptoms you might recognise in yourself after eating a plate of glutenous cacio e pepe.
But what if your negative symptoms were coming from your head, not your gut? Previous research suggests a feedback loop between food anxiety and flare-ups, meaning the more we worry a food will make us sick, the worse the response, and the more anxious we feel when faced with that food in future, and so on. Now, a new study has looked specifically at how that might impact gluten intolerance.
The study isn't suggesting you can cure celiac disease by changing your attitude to food, nor is it offering a solution to NCGS. Instead, it's looking at why gluten might cause negative symptoms in people with no medical or biological reason for it to do so.
The study
The study, published in The Lancet Gastroentorology & Hepatology, looked at expected gluten intake versus actual gluten intake impacted symptoms.
Researchers noted that "Anxiety and depression are more prevalent in people with NCGS than in the general population", stating that psychology can't be ruled out as a cause of gut reactions.
Nocebos - when harmless substances or behaviours lead to negative side effects because a patient believes they will occur - have also been shown to play a role in food intolerances, write the researchers. So, they looked at whether gluten specifically has a nocebo effect, recruiting 83 participants with self-reported NCGS and giving them gluten or non-gluten breakfasts and lunches.
The participants were assigned to one of the following groups:
Expectancy and intake: These participants were told they were eating gluten and did eat gluten.
Expectancy and no intake: These participants were told they were eating gluten but didn't eat any gluten.
No expectancy and intake: These participants were not told they were eating gluten but did eat gluten.
No expectancy and no intake: These participants were not told they were eating gluten and didn't eat gluten.
Participants were then asked to score their symptoms every hour after eating along a 10cm horizontal line, indicating 'no symptoms' at one end and worsening symptoms towards the other.
The results
The study found:
Those in the expectancy and intake group reported the highest symptom scores, marking symptoms an average of 1.66cm along the line.
Participants in the expectancy and no intake group showed moderately increased symptoms, marking 1.17cm along the line.
Eating gluten without knowing it didn't lead to a significant increase in symptoms, with participants marking just 0.6cm along the line.
The control group, who ate no gluten and hadn't expected to, had a similarly low symptom response, marking 0.7cm along the line.
People reported symptoms to be worse after lunch than after breakfast, suggesting repeated exposure (or expectation to exposure) increases side effects.
What this means for us
This study suggests that the nocebo effect is real when it comes to NCGS. There was no significant difference in symptoms between those who believed they were eating gluten, regardless of whether they really did, meaning what they thought they were eating played a more important role in triggering symptoms than what they actually ate.
The reason is because of the gut-brain axis, which shows how we think - consciously and subconsciously - affects how our gut works, and vice versa.
The researchers found gluten wasn't responsible for symptoms in any of the groups. This is not to say that participants symptoms weren't real - it just means the gluten itself wasn't the cause.
They also didn't offer advice on what to do if you believe you are sensitive to gluten. They note that more research is needed on the link between gluten, the brain, gut symptoms and the nocebo effect.
However, it's clear why so many people feel like gluten will trigger symptoms in them: misinformation around nutrition and the demonising of certain foods has infiltrated almost every form of health communication. Gluten in particular has been the recipient of some pretty bad PR over the past 10 years, so it's not surprising for you to have developed the belief that it's the cause of your problems.
Unlearning this, and re-wiring how you expect to feel around foods like gluten, could help reduce your symptoms in those with gluten sensitivities. This won't work in celiac disease, nor in some people with gluten sensitivities that are caused by biology rather than psychology.
The bottom line
This study shows the nocebo effect of gluten is real. That means, believing gluten is bad for you makes it bad for you.
There are limitations to who that applies to, of course, and it's not your fault if you think that way. You can blame the noise on social media and unqualified experts that categorise morally neutral foods into 'good' and 'bad'.
If you want to reintroduce gluten, or any other food you're sensitive to, it could be worth doing it with the help of a dietitian. But don't underestimate the often-elusive golden rule of listening to your body without storytelling - it might just help let you enjoy a regular croissant without pain.
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