Can Gluten Cause Anxiety and Brain Fog?
For some people, yes. Coeliac UK lists brain fog among the neurological symptoms of coeliac disease, anxiety and low mood are more common in people who have it, and plenty of people without coeliac disease report the same things lifting when they stop eating gluten. What's less clear is why, and in the non-coeliac case, whether it's gluten or wheat that's the issue. That matters, because it changes what you should do about it.
Having a gut that misbehaves is, in my experience, enough to make anyone anxious on its own. So it's worth separating out three things that get lumped together under "gluten makes me anxious".
If it's coeliac disease
This is the clear case. In coeliac disease, gluten triggers an immune reaction that damages the gut lining. Two things follow from that which reach well beyond the stomach. The lining stops absorbing nutrients properly, including iron, B12, folate and vitamin D, all of which affect mood, energy and concentration when they run low. And the body is carrying a low-level inflammation that affects how the brain works day to day.
A large UK study using Biobank data found that people with coeliac disease were more likely to show signs of anxiety and depression than people without it, and had slower reaction times. Brain fog, the feeling of not being able to think in a straight line or hold a sentence in your head, is one of the most commonly reported non-gut symptoms, and it is now being studied in newly diagnosed patients in the UK.
On a strict gluten-free diet these symptoms often improve, though the evidence is better for anxiety than for depression, and it's slow. The gut takes months to heal, so expect weeks to months rather than days.
If coeliac disease has been ruled out
This is where it gets more interesting.
People who test negative for coeliac disease but feel better off wheat are usually described as having non-coeliac gluten sensitivity. The symptoms are real. The question is whether gluten is the cause. In 2018 a Norwegian team ran the most careful test to date: 59 people with self-reported gluten sensitivity ate muesli bars for a week containing either gluten, fructans, or neither, without knowing which. Fructans gave them noticeably more symptoms than gluten did. Gluten was no worse than the placebo.
Fructans are a type of FODMAP, and wheat is one of the biggest sources of them in a Western diet, along with onion and garlic. So for a lot of people, going gluten-free works because it is accidentally a low-fructan diet. It's one study, it was small, it tested one dose and it measured gut symptoms more than mood, so it doesn't close the question. But it's a strong enough result that if you've gone gluten-free without a coeliac diagnosis and improved, it's worth asking whether it's really wheat and onions you're sensitive to rather than gluten. That's a different diet, and a much less restrictive one.
The gut itself
The third thing is simpler and gets overlooked because it isn't a diagnosis. Bloating, pain, urgency and never quite knowing what your gut is going to do are, by themselves, enough to keep anyone on edge. Bad sleep from gut symptoms makes thinking harder. Low iron from any cause makes you foggy and flat. And an elimination diet, however necessary, brings its own anxiety: the checking, the second-guessing, the fear of eating out. Some of what lifts when a diet starts working is simply that the gut has calmed down and you've stopped being frightened of food. That's a real improvement, but it isn't evidence that gluten was the culprit.
What to do, in order
1. Don't stop eating gluten before you've been tested. The coeliac blood test looks for your immune response to gluten, so if it's already out of your diet the test can come back clear even if you have the condition. If this post rings true, keep eating gluten as normal and ask your GP for the test. Coeliac UK's advice is the same, and their short online self-assessment is a sensible first step.
2. Ask for your iron, B12, folate and vitamin D to be checked at the same time. Low levels of any of them cause anxiety and fog in their own right, whatever the cause.
3. If coeliac disease is ruled out and you still feel better off wheat, test fructans rather than assuming gluten. The honest way to do it is a short, proper low-FODMAP trial with a dietitian, followed by a reintroduction of each group, rather than staying gluten-free for the rest of your life on a hunch.
4. If the fog and anxiety come with flushing, hives, a racing heart, or reactions to foods that have nothing to do with wheat, it's worth raising mast cell activation or histamine intolerance with your GP. Gluten gets blamed for a lot of things it didn't do.
5. Treat the anxiety as a thing in itself. Whatever food turns out to be doing, if anxiety is affecting your daily life it deserves its own conversation with your GP. Food can be part of the picture without being all of it.
If it turns out you do react to gluten, or to fructans, eating simply while things settle helps: plain meat, fish and eggs, rice, potatoes, and the fruit and veg you already know you tolerate. The food finder rates everyday foods on gluten-free and low-FODMAP side by side, which is useful when you're trying to work out which of the two is actually your problem.
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This article is general information, not medical or dietary advice. Anxiety and mood symptoms have many causes. If they're affecting your daily life, or you think gluten may be involved, speak to your GP, and keep eating gluten until any coeliac testing is complete.