The Gut-Brain Connection: How Nutrition Supports Nervous System Regulation

At Galena Wellness in Calgary, we often work with clients who are experiencing chronic stress, brain fog, low energy, digestive discomfort, anxiety or difficulty regulating their nervous system. While these concerns are complex, nutrition and gut health may play an important role in supporting brain function, inflammation regulation and resilience

Most of us think about mental health and nervous system regulation as something that

happens from the neck up. But your nervous system doesn't run on willpower alone — it

runs on fuel. What you eat determines whether your gut can produce the raw materials

your brain needs to regulate mood, manage stress, and stay resilient under pressure. And it

works both ways: chronic stress changes your gut, and a poorly-fed gut makes it harder to

handle chronic stress. If you're doing the work to regulate your nervous system and still

feeling sluggish, stuck, or wired-but-tired, your gut might be part of the story.

What Is the Gut-Brain Axis?

Here's the short version: your gut and brain are connected by a communication network

called the gut-brain axis, and the main cable running between them is the vagus nerve.

What surprises most people is that the traffic mostly runs one direction — from gut to brain,

not the other way around. Your gut is constantly sending your brain information about

what's going on inside you, and your brain is constantly responding.

Part of what makes this possible is the trillions of bacteria living in your gut. They don't just

help you digest food — they produce compounds your body uses to build

neurotransmitters and regulate inflammation. Healthy gut bacteria help process what you

eat into the raw materials your brain uses to build its own neurotransmitters. Protein gives

you amino acids like tryptophan and tyrosine — the actual building blocks for serotonin,

dopamine, and norepinephrine — and fiber gets fermented by gut bacteria into short-chain

fatty acids, which calm inflammation throughout your body and support brain function

along the way. Feed the bacteria well, and you're feeding the supply chain your brain

depends on. According to a review published in Frontiers in Neuroscience, the vagus nerve contains approximately 80% afferent and 20% efferent fibres.¹

How Does the Vagus Nerve Connect the Gut and Brain?

When your nervous system perceives a threat — real or remembered — it activates the HPA

axis, your body's central stress-response system. In short bursts, this is exactly what it's

supposed to do. But when stress becomes chronic, or when trauma keeps the alarm system

firing long after the danger has passed, that constant activation starts to narrow your

window of tolerance — the zone where you can handle stress without tipping into

shutdown or overwhelm.

Here's the part that often gets missed: that same stress activation changes how your gut

functions. Stress hormones like cortisol loosen the tight junctions between the cells lining

your gut — this is the mechanism behind what's often called "leaky gut" — which lets

bacterial fragments and inflammatory compounds slip into your bloodstream more easily

and drive inflammation throughout the body. Stress also thins the protective mucus layer

bacteria live in, and speeds up or slows down gut motility (how quickly things move

through your digestive tract), both of which make it harder for beneficial bacteria to hold

their ground. Over time, this shifts the balance of your gut community — fewer of the

beneficial species that produce calming, anti-inflammatory compounds, and more of the

species associated with inflammation. This is a big part of why chronic stress or trauma so

often shows up as low energy, exhaustion, tension, rumination, and irritability — it's not

just "in your head," it's a body-wide response, and the gut is caught in the middle of it.

The Feedback Loop Runs Both Directions

This is why the food piece isn't the whole story either. Just as poor gut health can make it

harder to tolerate stress, unresolved stress and trauma can directly disrupt digestion —

often through that same vagus nerve that connects gut and brain. When trauma keeps the

nervous system in a heightened state of arousal, vagal tone weakens, and with it, the body's

ability to send calming signals to the gut. This is a big part of why so many people with

PTSD or trauma histories also live with functional digestive issues that never quite resolve

with diet changes alone.

Therapies that help the nervous system process and release stored stress — like EMDR and

Somatic Experiencing — work directly with this pathway. EMDR has solid research support

for reducing trauma symptoms and body-based distress; clinically, many trauma therapists

see digestive symptoms ease as the nervous system settles and comes out of chronic threat

mode. That pattern makes sense given what we know about the vagus nerve, though the

research specifically measuring gut outcomes from these therapies is still catching up to

the clinical experience.

The takeaway isn't "do therapy instead of fixing your diet" or "fix your diet instead of doing

therapy." It's that both are legitimate entry points into the same system. If you've been

eating well and still feel stuck, the missing piece might be trauma processing or nervous

system work. If you've been doing that work and still feel physically depleted or inflamed,

food might be the piece that's been missing. Most people need both, working together,

rather than either alone.

What This Looks Like Day to Day

You don't need to overhaul your entire diet overnight. What matters most is the quality of

fuel you're giving your gut bacteria, and that mostly comes down to fiber and whole foods

versus refined ones.

Fiber is the primary food source for the beneficial bacteria that produce short-chain fatty

acids — the anti-inflammatory compounds that help keep your gut lining intact and calm

the kind of low-grade, body-wide inflammation that chronic stress feeds. Whole foods like

vegetables, fruit, oats, quinoa, beans, and root vegetables are rich in this kind of fiber, so

eating more of them gives beneficial bacteria more to work with, which helps them stay

dominant in your gut community and keep producing the compounds that support a

steadier stress response.

Refined foods — white bread, white pasta, most packaged snacks — do the opposite.

They're stripped of the fiber those bacteria need, and they spike blood sugar quickly, which

adds its own stress to the body. Over time, a diet low in fiber and high in refined

carbohydrates tends to favor less-helpful bacteria and shrink the population of the

beneficial ones, leaving your gut with a thinner buffer against the physical impact of stress

— right when you need that buffer the most.

In practice, this means "cleaning up your diet" isn't about restriction. It's about consistently

giving your gut bacteria the fiber-rich, whole foods they need to keep producing the

compounds that help your body absorb and recover from stress, rather than starving them

out with refined, low-fiber food and asking your nervous system to do all the work alone.

None of this replaces the regulation work you're already doing. Think of it as feeding the

system that makes the rest of that work possible.

The Bigger Picture

Your gut and your brain were never really separate systems — they've been in conversation

this whole time, whether you were paying attention or not. Building real resilience means

treating both sides of that conversation as part of the same work: giving your body the

nervous system regulation it needs to feel safe, and giving your gut the fuel it needs to

support that regulation from the inside out. Neither piece works as well without the other.

If you're already doing the work to regulate your nervous system and still feel stuck, it

might be worth asking what your gut has been trying to tell you.

Written by Anna Mehri, Registered Psychologist and Certified Holistic Nutritional Consultant

This article is for general educational purposes and is not a substitute for individualized medical, psychological or nutritional advice. Persistent digestive symptoms, unexplained weight changes, bleeding, severe pain or significant changes in bowel habits should be assessed by a qualified healthcare professional.