The Role of Food in Influencing Mental Health

Overview

The relationship between food and mental health is bidirectional: what we eat affects our mental wellbeing, and our mental state affects what we eat. This emerging field — nutritional psychiatry — is increasingly recognised in public health and food policy.

How Diet Influences Mental Health

The Gut-Brain Axis

The gut and brain are in constant two-way communication via the gut-brain axis — a network involving the enteric nervous system (the “second brain”), the vagus nerve, and the hypothalamic-pituitary-adrenal (HPA) stress axis.

• The gut produces approximately 90–95% of the body’s serotonin (the “feel-good” neurotransmitter)
• Gut microbiota produce neurotransmitter precursors and short-chain fatty acids (SCFAs) that influence brain function and mood
• A healthy, diverse gut microbiome is associated with lower rates of anxiety and depression
• Disruption to gut microbiota (dysbiosis) — caused by a diet high in ultra-processed foods, low in fibre — is linked to increased inflammation, which is implicated in depression

Nutrients Critical for Brain Function

Deficiencies in these nutrients — common in restrictive, monotonous, or ultra-processed food diets — can directly impair brain function and contribute to mood disorders.

Dietary Patterns and Mental Health Outcomes

Research consistently shows that dietary patterns — not just individual nutrients — matter:

• Mediterranean-style diet (vegetables, legumes, wholegrains, fish, olive oil): associated with 25–35% lower risk of depression
• Western diet (high in UPFs, refined carbohydrates, added sugars): associated with higher rates of depression and anxiety
• The SMILES trial (2017, Australia): a randomised controlled trial that showed dietary improvement significantly reduced depressive symptoms compared to social support alone — groundbreaking evidence that diet can be a therapeutic intervention for depression

Bidirectionality: Mental Health Affects Eating

Mental health conditions alter eating patterns:

• Depression: Often leads to appetite loss or comfort eating; motivation to cook declines; energy-dense convenience foods become default choices
• Anxiety: May cause nausea, food avoidance, or disordered eating behaviours around specific foods
• Stress: Cortisol increases cravings for energy-dense, high-fat, high-sugar foods — the “stress eating” response has evolutionary roots (seeking quick energy in perceived danger)
• Sleep deprivation: Increases ghrelin (hunger hormone) and decreases leptin (satiety hormone), promoting overconsumption of discretionary foods

This bidirectionality can create self-reinforcing cycles: poor diet → worse mental health → further dietary decline.

Disordered Eating and Mental Health

• Orthorexia (obsession with healthy eating), anorexia nervosa, and binge-eating disorder are serious mental health conditions with significant nutritional consequences
• Restrictive dieting and body dissatisfaction are linked to anxiety and depression, particularly among adolescents
• Social media diet culture can intensify these pressures through idealised body images and moralising food messaging

Food, Mental Health and Public Policy

The growing evidence base for diet-mental health links has prompted interest in:
- Including nutrition counselling in mental health treatment plans
- Food prescription programs for people experiencing depression
- School-based nutrition programs addressing both physical and mental wellbeing

KEY TAKEAWAY: Food influences mental health through the gut-brain axis, neurotransmitter synthesis, and anti-inflammatory mechanisms. The relationship is bidirectional — mental health conditions also alter eating behaviours, creating potential cycles of decline.

EXAM TIP: Use precise scientific language: “gut-brain axis,” “serotonin,” “omega-3 fatty acids,” “cortisol.” Avoid vague statements like “healthy food makes you feel better” — link mechanisms to outcomes.

REMEMBER: The SMILES trial is a notable Australian study supporting nutritional intervention for depression — useful evidence to cite in extended response questions about diet and mental health.