Why We Can’t Talk About Gut Health Without Talking About the Nervous System
There is a unique quality to the angst of living with a gut that feels like a full-time job: scanning for patterns - like the spaghetti bolognese that leaves you painfully bloated and drives you to cut out gluten, only to share pizza with friends at the new Italian place a few weeks later that you walk away from symptom-free; or the days you skip lunch at work because you can’t afford to keep rushing to the toilet all afternoon, heart pounding, body tight… only to find that on holiday - when the days are slower and your shoulders finally drop - you can eat freely and your digestion seems to move with ease.
And there’s the tests… the bloods, the scopes, the imaging, the stool samples: clear, clear, clear, and clear. No inflammation markers. No disease. A resounding ‘good news - you’re all clear!’ from the specialists.
And you’re left with a gut that seems to turn against you without warning, and a head full of questions:
Am I imagining this?
Is it all in my head?
Why doesn’t my body make any sense?
And it’s often here, in this gap between symptoms and explanations, that people begin to blame themselves. Or tighten their grip on food. Or feel quietly dismissed by a system that can’t quite hold the whole picture of a gut that isn’t malfunctioning, but responding.
What the gut actually needs to function
For digestion to unfold smoothly - for the stomach to secrete acid, for the intestines to move rhythmically, for nutrients to be absorbed and waste to be released - the body needs a very specific internal condition: a sense of relative safety. From a physiological perspective, digestion is governed largely by the parasympathetic branch of the autonomic nervous system - often referred to as the “rest and digest” state. This is the state in which the body can soften, open, and coordinate complex internal processes without urgency.
What this means, is that when the nervous system perceives safety, digestion is supported. When the nervous system perceives threat, even subtle ongoing threats (like those emails that you still haven’t gotten around to sending, or the relentless internal dialogue of self-criticism), digestion changes.
This is actually the wisdom of biology, not a personal failing or a psychological flaw. In evolution’s brilliance, our guts are entwined with nerves - this way, the gut can be in constant communication with the brain, and is able to respond to what we eat, and how safe the body feels while eating, digesting, and living.
So, when digestion feels unpredictable or inconsistent, this tells us the conditions it needs are not reliably present.
How nervous system states shape gut symptoms
When the nervous system moves into fight-or-flight, digestion is bumped to the bottom of the priority list. Adrenaline and cortisol (our stress hormones) help redirect blood flow away from the gut. Gut motility may speed up or become erratic. Sensation can heighten, making normal digestive processes feel painful or alarming.
This can show up as:
urgency or diarrhoea
cramping or pain after meals
bloating that seems disproportionate
heightened sensitivity to foods that are otherwise tolerated
In contrast, when the nervous system shifts toward shutdown or collapse - a state many people live in after long periods of stress or overwhelm - digestion can slow dramatically. Motility decreases. Appetite may dull. Constipation, nausea, or a heavy, stuck feeling can emerge.
Neither of these states are “wrong” - indeed, they are simply biology in the service of survival; the body doing its best to protect itself based on the information it’s receiving.
But this is also why gut symptoms can look so utterly contradictory: why the same food can feel intolerable one day and completely fine the next; why eating at work feels impossible, while eating on holiday feels easy; why restriction or control might seem to help for a moment, then make everything worse.
Your gut is not ignoring logic; it is responding to context.
And when the nervous system is chronically activated - through stress, trauma, perfectionism, hypervigilance, or long-term pressure - the gut often becomes the canvas on which these stories are painted.
[A brief note on the science behind this - feel free to skip]
There is a well-established scientific framework that helps make sense of these patterns: psychoneuroimmunoendocrinology, often shortened to PNIE.
PNIE describes the constant, two-way communication between the nervous system, the immune system, the endocrine (hormonal) system, and the gut. Rather than operating as separate systems, they function as an integrated network - continuously responding to signals of safety, threat, nourishment, and stress.
From this perspective, it makes complete sense that:
chronic stress can alter gut motility and sensitivity
immune activation can affect digestion and tolerance
hormonal shifts can change appetite, bowel patterns, and inflammation
and nervous system states can shape how food is processed and experienced
This isn’t abstract theory. It’s why the same person can tolerate foods differently depending on context, safety, and internal state - and why gut symptoms so often fluctuate alongside emotional and physiological stress.
When we view gut health through a PNIE lens, symptoms are no longer mysterious or random. Quite the opposite, in fact: they are meaningful responses within an intelligent, adaptive system.
Why food changes alone often don’t bring relief
When gut symptoms flare, it makes sense to look to food. Food is tangible. It’s something we can change, control, eliminate, or optimise. And sometimes, food does play a role, for example allergies, intolerances, and medical conditions are real, and nutrition science matters.
But for many many people, food is only part of the story.
If the nervous system is consistently perceiving threat, removing or changing foods may offer temporary relief without addressing the underlying conditions driving the symptoms. In some cases, it can even increase vigilance - the body becoming more watchful, tense, and alert to potential danger.
This is often why people find themselves cycling through:
elimination diets that help briefly, then stop working
supplements that feel promising, then fall flat
protocols that look good on paper but feel unsustainable in real life
It isn’t because the person hasn’t found the right food yet, but because digestion does not happen in isolation from the rest of the body.
When the nervous system is constantly braced, the gut receives mixed signals. Even the most carefully chosen foods cannot override a body that does not feel safe enough to digest, absorb, and move things through.
This doesn’t mean nutrition is irrelevant. It means nutrition needs to be held within a wider lens that includes the nervous system, lived experience, and the realities of stress and trauma.
When gut health and disordered eating histories intersect
For those with a history of dieting, restrictive eating, or eating disorders, this dynamic becomes even more complex.
Many people arrive at gut work already carrying years of:
food rules
moral language around eating
fear of “getting it wrong”
a belief that the body must be controlled to function
When gut symptoms appear in this context, food restriction can feel not only logical, but necessary. Symptoms become proof that the body cannot be trusted, and control tightens, while safety gets outsourced to lists, plans, and avoidance. And in the background workings of your divinely wise body, restriction itself is a powerful nervous system stressor.
Irregular eating, under-fuelling, and fear around food can keep the body in a state of ongoing activation that directly undermines digestion: the gut becomes more sensitive, not less. Symptoms escalate, rather than resolve.
This can be deeply confusing and painful.
People often tell me: “I’m doing everything I’m supposed to do - why is my gut getting worse?”. Or quietly wonder if healing simply isn’t possible for them.
In these moments, it’s important to say this clearly and without judgement: Your body is not sabotaging you. It is responding to the conditions it’s been living in.
It’s why gut healing comes from slowly creating the conditions in which it no longer needs to stay on guard.
What a nervous-system-informed approach to gut health looks like
A nervous-system-informed approach to gut health doesn’t begin with restriction or optimisation. It begins with listening.
It recognises that before the gut can digest food, the body needs to sense enough safety to soften, receive, and let go. That safety is built slowly, through consistency, attunement, and practices that help the nervous system come out of chronic vigilance.
This kind of work often includes:
creating regularity with meals, rather than perfection
supporting digestion through rhythm and predictability
reducing urgency around symptoms, rather than escalating it
gently widening the body’s capacity to tolerate sensation
tending to stress, overwhelm, and emotional load alongside food
Importantly, this is not about “thinking your way” out of symptoms, but about working with the body’s physiology through supporting the nervous system so the gut no longer needs to stay on high alert.
For many people, this brings a profound shift: symptoms that once felt chaotic begin to make sense, and the body becomes less reactive as it is met with enough steadiness to stand down. In this way, healing is a non-linear process of rebuilding trust with food, with the body, and with the signals that were once frightening or confusing.
How I hold this work in practice
In my work, gut health is never treated in isolation. I work with women who feel stuck in their relationship with food and their bodies, often after years of trying to “do the right thing.” Together, we explore not only what you eat, but the conditions in which eating, digesting, and living are happening, and what messages your nervous system learned in your formative years about nourishment - its availability, accessibility, and the felt sense of safety around it.
This work integrates nutrition science with nervous system awareness, body-based exploration, and a trauma-informed lens. We move slowly. We prioritise safety and consent. We make room for complexity, especially when symptoms intersect with disordered eating histories, chronic stress, or long-held patterns of self-control.
Rather than asking the body to behave, we become curious about what it has been carrying, and what it might need now.
If you’d like to learn more about working together, you can explore my one-to-one somatic nutrition therapy offerings below.
And if you’re curious about the deeper science behind the gut–nervous system relationship, I’ll be sharing a more detailed exploration of the PNIE framework in a future post.
This way of listening to the body is the foundation of my work at Alitus.
In sessions, we explore food, physiology, and the nervous system together - gently, lovingly, collaboratively, and at a pace your body can tolerate. There is no pressure to fix or override what is happening. Instead, we build safety, curiosity, and relationship, allowing the body’s patterns to be met with understanding rather than force.
If this perspective resonates, you can learn more about working together.