Can diets really impact psychiatric and brain health?

An extraordinary amount of scientific research reveals how conditions previously considered exclusively brain-related, commence as metabolic dysfunction. Metabolic dysfunction is inherent to the pathophysiology of mental illness.

Nutritional psychiatry is a growing sub-specialty of psychiatry. The brain consumes 20% of energy - this includes not only calories - but fats, proteins, vitamins, minerals and other compounds, but our nutrient guidelines are not directed to ensuring that brain health is optimised. The brain's metabolism is dependent on nutrients to work.

'The brain "punches above its weight,” needing to be fed as much as 10 times the amount of blood you would expect for an organ so small. Similar numbers apply to children, depending on their age and weight. In general, the brain consumes 20–40% of the nutrients and energy we ingest, which is disproportionately higher than its weight' (Rucklidge, Johnstone, Kaplan 2021).'

Mechanistic, observational and interventional data increasingly demonstrates that diet is a modifiable risk factor for mental illness. Studies researching nutrition and psychiatry have exploded in the past 15 years.

‘nutritional psychiatry encompasses the study of dietary and nutrient-based interventions for the prevention or treatment of mental disorders. The concept of nutraceuticals refers to non-toxic dietary extracts or supplements with scientifically validated benefits for promoting health and aiding in disease management.’ (Borrego-Ruiz & Borrego 2025)

PSGRNZ emphasise that psychotherapy, connection and support play an integral part of healing and management of brain and mind-related challenges. Human connection is central to the healthy functioning of all of us. The greater outcome from psychotherapy, friendship and community engagement includes deeper self-understanding, enhanced self-agency, and greater social engagement.

Nutritional psychiatry which integrates nutritional and dietary changes, complements traditional psychotherapy. Nutritional psychiatry may play a key role in supporting children and young people who are going through developmental phases, women before, during and after pregnancy, and in supporting people who are treatment resistant to conventional psychiatric drugs, or find adverse drug events overly uncomfortable. These groups may particularly benefit from such an approach, but there is evidence that people with a wide range of brain and nervous-system diagnoses, including OCD, schizophrenia, ADHD, depression, anxiety and autism experience improvements in sleep, concentration, and wellbeing from a nutritional approach that is targeted to optimising brain health.

The evidence strongly suggests that dietary modifications, and in many cases, high dose multinutrient formulations which are targeted to optimising brain health are an underutilised tool for people diagnosed with a psychiatric condition. People are not normally deficient in one nutrient, and as Reclaiming Health discusses, conventional macronutrient and micronutrient health agency recommendations are based on preventing deficiency.

The New Zealand health system contains no information on the role of macronutrients and micronutrients in addressing deficiency or insufficiency, i.e., in supplying sufficient levels of nutrients that not just sustain whatever level is currently in the body, but replenish the entire body to optimise brain health.

Poor dietary and nutrient intakes promote inflammation, and amplify negative feedback loops that can overwhelm the body’s capacity to repair. The central nervous system and the digestive tract are inter-dependent. A healthy microbiome is essential to optimise bi-directional neuroendocrine signalling, for sensory-motor reflexes, immune activation, gut brain cross-talk and hormonal signalling.

Biomarker studies have tracked relationships between diet quality, metabolic health, and risks for mental disorders including anxiety, depression, addiction and suicidality. Risk factors can overlap, amplifying conditions or increasing the severity of symptoms and diseases.

Chapter 3 discusses psychiatric nutrition, while chapter 4 looks at the problem of food addiction which may intersect with a psychiatric diagnosis, particularly in young people, and chapter 5 discusses the burden on young people when they are diagnosed at earlier and earlier ages. Chapters 11 and 12 outline reform recommendations for supporting dietary change but also for supporting high dose nutrition as a therapeutic option for treatment of psychiatric illnesses.

PSGRNZ (2026) Reclaiming Health: Reversal, Remission & Rewiring. Understanding & Addressing the Primary Drivers of New Zealand’s Metabolic & Mental Health Crisis. Bruning, J.R., Physicians & Scientists for Global Responsibility New Zealand. ISBN 978-1-0670678-2-3

Can diets really impact psychiatric and brain health?

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