Working with the gut-brain axis for mood and anxiety

How targeted nutrition + supportive counselling can improve digestion and mental wellbeing

Most people have felt it: butterflies before a big moment, nausea with stress or that “gut-wrenching” sensation when something feels wrong. This reflects a two-way communication system between your digestive tract and your brain.

Research describes this as the gut–brain axis; it helps explain why emotional stress can flare digestive symptoms and why gut dysfunction can feed into low mood, anxiety and depressive symptoms. [1-8]

But, because the gut–brain axis is influenced by diet, microbiome balance, inflammation and stress physiology, it also creates multiple practical entry points for change—especially through nutrition and counselling support.[1]

What is the gut–brain axis (and why does it matter for mental health)?

The gut–brain axis is a bidirectional network linking the gut, the gut microbiome (your intestinal microbes) and the brain through several overlapping pathways.

Two of the most important “messenger highways” are: [1-3]

1) The vagus nerve: A direct communication line

Research highlights the vagus nerve as central to gut–brain crosstalk, helping explain why emotions can show up as gut sensations and why gut function can influence emotional state.

2) The hypothalamic-pituitary-adrenal (HPA) axis: Immune + inflammation + stress hormones

The gut microbiota can influence the brain through signalling molecules travelling via the bloodstream and across the blood–brain barrier, with the immune system acting as a key pathway. When the gut–brain axis is disrupted, it may contribute to chronic inflammation and hyperactivity of the HPA axis (stress system)—patterns linked to stress-related conditions.

Importantly, it’s not one-way: Stress can worsen gut inflammation and dysregulate the gut–brain axis, helping explain why stress often aggravates conditions like irritable bowel syndrome (IBS) and other inflammatory gut disorders.

How gut imbalance can feed anxiety and low mood

When the gut microbiome is unbalanced (“dysbiosis”), evidence links this dysfunction to anxiety- and depressive-like behaviours, likely via immune activation, stress-system changes and altered signalling metabolites. [1,2]

There’s also growing attention on gut integrity (“barrier function”). Stress and inflammation can increase gut permeability, allowing bacterial components to interact more strongly with the immune system—one pathway proposed in depression symptom risk. [3]

How diet shapes mood through the gut–brain axis

Diet is one of the most powerful modifiable influences on gut microbiota and inflammation—and therefore on gut–brain signalling. [1-8]

Patterns linked with lower anxiety (and better overall mental health)

A large scoping review on diet and anxiety found that lower anxiety is associated with “healthy” dietary patterns (including Mediterranean/traditional-style patterns), typically emphasising vegetables, fruit, minimally processed foods, and limiting sugar and refined grains. [5]

The same review mapped consistent associations between higher anxiety and diets high in sugar/refined carbohydrates and other “unhealthy” patterns. [5]

Ultra-processed foods: A consistent red flag

Other research reports that higher intake of ultra-processed foods correlates with poorer mental health functioning, while higher whole-food intake correlates with better mental health functioning; improvements in diet quality over time were associated with improved mental health. [2,4]

The Mediterranean-style way of eating found to be beneficial

Moving toward a nutrient-dense, Mediterranean-style pattern of eating has been found to improve depression outcomes—most famously the Australian SMILES trial, which involved structured dietitian support and showed larger mood improvements than a social-support control. [2]

The nutrient story: Food supplies mood-building ingredients

Your diet also supplies the building blocks for neurotransmitters and brain regulation, including tryptophan, B vitamins (B6, B12, folate), choline and amino acids, alongside omega-3 fats that support serotonergic and dopaminergic function. [1-8]

Micronutrient adequacy also matters because nutrients can influence neurotransmitter activity, oxidative stress, inflammation and the stress system (HPA axis) that influence the depression burden.

Where counselling fits (and why it’s not “optional”)

If nutrition is the fuel for the gut–brain axis, counselling is often the steering wheel—because stress physiology directly influences gut inflammation and gut–brain signalling. [1,6,7]

A holistic approach—integrating conventional care with nutrition, gut microbiome support and lifestyle strategies—may be more effective than focusing on one factor alone.

If you or someone you care about is experiencing severe distress, thoughts of self-harm, or feels unsafe, please seek urgent support immediately—call your local emergency number (000 in Australia), contact Lifeline on 13 11 14, or go to your nearest emergency department.

References: [1] Merino Del Portillo M, et al. Nutritional modulation of the gut-brain axis: A comprehensive review of dietary interventions in depression and anxiety management. Metabolites 2024 Oct 14;14(10):549. [2] Rucklidge JJ, et al. Nutrition provides the essential foundation for optimizing mental health. Evidence-Based Practice in Child and Adolescent Mental Health 2021;6(1):131-154. [3] Grajek M, et al. Nutrition and mental health: A review of current knowledge about the impact of diet on mental health. Front Nutr 2022;9:943998. [4] Gheonea TC, et al. Nutrition and mental well-being: Exploring connections and holistic approaches. J Clin Med 2023;12(22):7180. [5] Aucoin M, et al. Diet and anxiety: A scoping review. Nutrients 2021;13(12):4418.  [6] Rychescki GG, et al. Online cognitive-behavioral therapy-based nutritional intervention via instagram for overweight and obesity. Nutrients 2024;16(23):4045. [7] Muscaritoli M. The impact of nutrients on mental health and well-being: insights from the literature. Front Nutr 2021;8:656290. [8] Granero R. Role of nutrition and diet on healthy mental state. Nutrients 2022;14(4):750.