Why we ask about your gut.
A patient comes in for cognitive symptoms. We ask about their bowels, their bloating, their reflux, their relationship with eating. Some patients are surprised. A few are mildly affronted. The honest answer is: we ask because the literature increasingly says we should — and because, occasionally, the answer reframes the entire intake.
The gut–brain axis isn't a wellness slogan
The bidirectional communication between the enteric nervous system, the vagus nerve, the immune system, and the central nervous system is now an established research field with its own journals, conferences, and growing evidence base. [1] The vagus nerve carries about 80% of its fibres up from the gut to the brain, not the other way around. The gut microbiome produces neurotransmitters and metabolites that influence brain function. Inflammation in the gut produces cytokine signals that reach the brain.
None of this is recent — Hippocrates flagged the connection — but the mechanistic detail has been worked out in the last twenty years, and the clinical implications are still being mapped. The wellness industry got there first, often with claims well ahead of the data. The empirical literature is more interesting and more carefully scoped than either the slogans or the dismissals tend to acknowledge.
What we're looking for in intake
Several gut-related findings, when present alongside cognitive or mood symptoms, are clinically interesting:
- Persistent bloating, abdominal distension, or post-meal discomfort.
- Significant changes in bowel habit — frequency, consistency, urgency — that have evolved over the same period as the cognitive symptoms.
- Reflux, heartburn, or acid suppression medication use over years.
- Dietary restrictions or aversions that have crept in over time, particularly to specific food groups.
- History of antibiotic exposure, particularly multiple courses, in the same window the symptoms emerged.
- Coeliac disease, inflammatory bowel disease, or significant gut surgery in personal history.
- Significant unintentional weight change in either direction.
The reason isn't that any of these is the cause of the cognitive picture. It's that gut-related findings can:
- Indicate ongoing low-grade systemic inflammation that affects brain function. [2]
- Indicate nutrient absorption problems — B12, iron, vitamin D, magnesium — that often present cognitively before they present anywhere else.
- Indicate pharmacological side-effects (long-term proton-pump inhibitor use is associated with B12 deficiency, for example) worth raising with the patient's GP.
- Indicate a stress-driven autonomic picture where gut and brain are both downstream of the same regulatory issue.
What we don't do
We don't order pathology. We don't diagnose IBS, SIBO, coeliac disease, IBD, or any other gastroenterological condition. We don't recommend exclusion diets without indication. We don't sell supplements.
What we do is identify gut-side findings that warrant attention, refer to GPs and dietitians where appropriate, and integrate the picture into the clinical formulation. If the qEEG is suggestive of inflammatory contributors and the gut history is suggestive of inflammatory contributors, that's a coherent picture worth acting on — usually starting with the GP and a dietitian, not with us.
Where the literature is still working things out
Several questions remain genuinely open. The relationship between specific microbiome compositions and specific psychiatric presentations is correlational and inconsistent across studies. [3] Probiotic supplementation as a treatment for cognitive or mood symptoms has shown small effects in some trials and none in others. The clinical utility of microbiome testing in healthy adults is, at present, marginal.
What is established is the bidirectional communication itself, the relevance of inflammatory and nutritional inputs to brain function, and the value of taking a gut history seriously when cognitive symptoms are presenting. That's enough to ask the questions. It's not enough to claim that fixing the gut fixes the brain.
The honest summary
We ask about the gut because the literature increasingly suggests we should — and because, in clinic, the answer occasionally reframes the entire picture. We don't treat the gut. We don't sell anything. We listen for the inputs that most workups skip, and we route to the practitioners best placed to act on them.
The gut–brain axis is not folklore. It's also not the answer to everything. It is, like most useful clinical questions, somewhere in between.
About the author. Dr Ash Connell is a chiropractor (AHPRA CHI0001772308), board-certified in quantitative EEG (QEEG-D), and the founding clinician of The Healthy Brain Clinic. He practises from Geelong and Camperdown, Victoria, and online Australia-wide. Read his bio →
References
- Mayer EA, Tillisch K, Gupta A. (2015). Gut/brain axis and the microbiota. Journal of Clinical Investigation, 125(3), 926–938.
- Cryan JF et al. (2019). The microbiota–gut–brain axis. Physiological Reviews, 99(4), 1877–2013.
- Valles-Colomer M et al. (2019). The neuroactive potential of the human gut microbiota in quality of life and depression. Nature Microbiology, 4, 623–632.
Editorial note. This article was drafted by Dr Ash Connell with structural support from a large language model, then reviewed for clinical accuracy and AHPRA compliance before publication. Citations are real, peer-reviewed sources. The clinical interpretations are Dr Ash's own.
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This article is general health information, not personalised clinical advice. It isn't a substitute for assessment by a registered health practitioner. If you or someone you know is in crisis, call 000 or Lifeline 13 11 14.