A claim you hear on longevity podcasts

Does gluten cause brain fog without celiac disease?

The claim checked: Gluten causes brain fog in some people without celiac disease, and dropping it helps Hear it at 13:30

What do the studies say?

Leaning for

Two trials found symptoms such as tiredness eased off gluten or rose on it. In two blinded trials, gluten had no effect of its own. Six more found gluten mattered for some people only, or could not tell it apart from a placebo. In one, about 14% met the bar for gluten sensitivity.

Computed from 10 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.

What was said on the podcast?

“I've seen thousands of patients struggling with brain fog, with fatigue, with digestive issues, with joint pain, skin problems, even autoimmune conditions, who experience remarkable improvements after removing gluten for a period of time and then carefully reintroducing it.”
Mark Hyman, The Dr. Hyman Show · 5 Foods That Are Making Your Brain Fog Worse · 13:30 on YouTube
The point checked Leaning for

In people without celiac disease or wheat allergy, gluten can cause symptoms such as brain fog and fatigue, and removing it improves them

Agree 2

controlled trial · 2020

“Furthermore, such extra-intestinal symptoms as fatigue and weakness (P = 0.000), musculo-skeletal pain (P = 0.000) and headache (P = 0.002) improved in NCGS patients on GFD.”

Prevalence of Non-Celiac Gluten Sensitivity in Patients with Refractory Functional Dyspepsia: a Randomized Double-blind Placebo Controlled Trial. Sci Rep
Who: 77 Iranian adults aged 18-55 with refractory functional dyspepsia, celiac disease, wheat allergy and H. pylori excluded; 27 gluten-free-diet responders entered the blinded challenge
PMID 32051513

controlled trial · 2015

“The statistical analysis showed that the differences between gluten-containing and placebo groups in the overall symptoms (placebo (16.2%), gluten (74.3%)) including satisfaction with stool consistency (placebo (8.1%), gluten (77.1%)), tiredness (placebo (8.8%), gluten (60%)), nausea (placebo (5.4%), gluten (8.3%)), bloating (placebo (16.2%), gluten (74.3%)) were statistically significant ( p = 0.001).”

Non-Celiac Gluten Sensitivity Has Narrowed the Spectrum of Irritable Bowel Syndrome: A Double-Blind Randomized Placebo-Controlled Trial. Nutrients
Who: Adults (>16 years) with newly diagnosed IBS (Rome III) at a Tehran outpatient clinic, CD and wheat allergy excluded, who responded to a 6-week gluten-free diet
PMID 26056920

Partly agree 6

controlled trial · 2016

“However, following a conservative profile and considering half of patients responsive to gluten as “false” responders (taking into account the percentage of placebo responders), about 14% can be considered NCGS.”

Evidence for the Presence of Non-Celiac Gluten Sensitivity in Patients with Functional Gastrointestinal Symptoms: Results from a Multicenter Randomized Double-Blind Placebo-Controlled Gluten Challenge. Nutrients
Who: Adults aged 18-75 at 15 Italian gastroenterology outpatient centers with functional GI symptoms (Rome III), CD and wheat allergy excluded; 87% female
PMID 26867199

controlled trial · 2015

“In conclusion, in the present trial, most patients showed approximately equal degrees of overall symptoms with either gluten or placebo, although overall symptoms were worsened significantly by gluten in comparison with placebo.”

Small Amounts of Gluten in Subjects With Suspected Nonceliac Gluten Sensitivity: A Randomized, Double-Blind, Placebo-Controlled, Cross-Over Trial. Clin Gastroenterol Hepatol
Who: 61 adults without celiac disease or wheat allergy, referred to 2 Italian celiac centers with intestinal and extraintestinal symptoms they attributed to gluten (suspected NCGS); 53 female, mean age 39.3
PMID 25701700

other primary study · 2017

“These findings reveal heterogeneity and potential methodology flaws among studies of gluten challenge, cast doubt on gluten as the culprit food component in most patients with presumptive NCGS, and highlight the importance of the nocebo effect in these types of studies.”

Suspected Nonceliac Gluten Sensitivity Confirmed in Few Patients After Gluten Challenge in Double-Blind, Placebo-Controlled Trials. Clin Gastroenterol Hepatol
Who: Adults with suspected NCGS or IBS improving on a gluten-free diet, celiac disease excluded, in 10 double-blind placebo-controlled gluten-challenge trials
PMID 27523634

Show 3 more Show fewer

trial or observed group · 2021

“Twenty-seven (54%) participants were gluten responsive (NCGS), and 23 were placebo responsive, with an order effect.”

Non-Celiac Gluten/Wheat Sensitivity: Clinical Characteristics and Microbiota and Mycobiota Composition by Response to the Gluten Challenge Test. Nutrients
Who: 50 adults (43 women, mean age 42) in Torino, Italy with self-reported gluten/wheat sensitivity, celiac disease, wheat allergy and IBS excluded
PMID 33921293

other primary study · 2014

“The present study provides a picture of suspected NCGS, but we must emphasize the major limitation of the study, namely that the diagnosis of NCGS remained highly presumptive in all our patients, because it was not established by a confirmatory DBPC.”

An Italian prospective multicenter survey on patients suspected of having non-celiac gluten sensitivity. BMC Med
Who: Patients with suspected NCGS (CD and wheat allergy excluded) seen at 38 Italian referral centers for gluten-related disorders; 84% female, mean age 38
PMID 24885375

pooled analysis · 2018

“We found a trend towards worsened depressive symptoms during the gluten challenge period compared to placebo, although this did not reach significance (SMD 0.21, 95% CI −0.58 to 0.15; p = 0.25).”

Mood Disorders and Gluten: It's Not All in Your Mind! A Systematic Review with Meta-Analysis. Nutrients
Who: Prospective studies of gluten-free diet or gluten challenge in people with coeliac disease, IBS or NCGS (75.8% Finnish participants); depressive symptoms as outcome
PMID 30413036

Disagree 2

controlled trial · 2013 · landmark

“In conclusion, these consecutive double-blind, randomized, placebo-controlled, cross-over rechallenge studies showed no evidence of specific or dose-dependent effects of gluten in patients with NCGS placed on a low FODMAP diet.”

No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates. Gastroenterology
Who: 37 adults aged 24-61 (6 men) with self-reported non-celiac gluten sensitivity and IBS (Rome III), celiac disease excluded; 22 returned for a 3-day rechallenge
PMID 23648697

controlled trial · 2025

“While these individuals experienced increased fatigue after acute challenge and heightened GI symptoms during sub‐acute exposure, these responses were not gluten‐specific.”

Impact of Acute and Sub-Acute Gluten Exposure on Gastrointestinal Symptoms and Psychological Responses in Non-Coeliac Gluten Sensitivity: A Randomised Crossover Study. United European Gastroenterol J
Who: 16 adults with self-reported NCGS on a strict gluten-free diet (coeliac excluded) and 20 healthy controls, University Hospital Leuven
PMID 40138597

What else was said but not tested?

  • Gluten should be one of the first foods to investigate for unexplained brain fog

More on food and fasting

All checked claims · How we check a claim

How Precis checks a claim · Report an error

The Precis Weekly

Get each new check by email.

One email a week with the claims and episodes we checked, what the studies found and the minute each claim was said.

Free. Unsubscribe anytime.