Metabolic health, nutrition and mental health

10 September was World Suicide Prevention Day. The World Health Organization estimates that 727,000 people died by suicide in 2021. Suicide was the third leading cause of death among 15- to 29-year-olds, and 73% of deaths occurred in low- and middle-income countries [1]. These deaths cannot be explained by one diagnosis, one social problem, or one nutrient. Suicide is complex, and anyone at immediate risk needs urgent human and clinical support.

But complexity should not become an excuse for ignoring biology. The brain is an energy-demanding organ, built from nutrients and influenced by insulin signalling, inflammation, oxidative stress, hormones, sleep and mitochondrial function. Metabolic psychiatry asks a deceptively simple question: what if some psychiatric symptoms are affected not only by neurotransmitters and life experience, but also by how the brain produces and regulates energy?

The epidemiology supports taking that question seriously. A meta-analysis found that people with depression had a 60% higher risk of later developing type 2 diabetes, while people with diabetes had a 15% higher risk of developing depression [2]. Another large meta-analysis estimated that metabolic syndrome was present in 32.6% of people with severe mental illness [3]. Medication effects, poverty, stress, sleep, inactivity and diet all contribute, so these figures do not prove that metabolic dysfunction causes mental illness. They do show that treating mind and metabolism as unrelated systems makes little sense.

Dietary intervention evidence is strongest for depression. A meta-analysis of 16 randomised trials involving 45,826 participants found that dietary interventions produced a small but significant reduction in depressive symptoms, although most participants had not been recruited specifically for clinical depression. No significant overall effect was found for anxiety [4]. In the 12-week SMILES trial, 32.3% of adults receiving structured dietary support achieved remission from major depression, compared with 8.0% in the social-support control group [5]. This was a modified Mediterranean-style intervention, not a ketogenic diet, and the trial was small. Its importance is broader: changing whole-diet quality may have measurable psychiatric effects.

The ketogenic question is more experimental. Clinicians and writers including Georgia Ede, Christopher Palmer, Lori Calabrese and Nicole Laurent have helped bring this metabolic lens into public view. Ketogenic therapy already has a long clinical history in drug-resistant epilepsy and may influence brain fuel availability, mitochondrial function, inflammation and neuronal signalling. In a four-month Stanford pilot involving 23 adults with bipolar disorder or schizophrenia who continued standard treatment, 79% of those who began with elevated symptoms improved by at least one point on the Clinical Global Impression severity scale, alongside improvements in weight and metabolic markers [6]. Encouraging, yes. Proof, no. The study was small, single-arm, and unable to separate the diet effect from support, expectation or other changes. A randomised trial is registered to investigate the approach further [7].

The responsible conclusion is neither that food is irrelevant nor that food is a cure. A nutrient-dense, minimally processed diet, adequate protein, stable access to food, movement, sleep and metabolic screening belong inside mental healthcare. For some patients, medically supervised carbohydrate restriction or ketogenic therapy may eventually become a useful adjunct. It should not replace psychotherapy, medication, crisis care or social support, and psychiatric medication should never be stopped without medical supervision.

References

1. World Health Organization. Suicide worldwide in 2021: global health estimates. Geneva: World Health Organization; 2025. https://www.who.int/publications/i/item/9789240110069
2. Mezuk B, Eaton WW, Albrecht S, Golden SH. Depression and type 2 diabetes over the lifespan: a meta-analysis. Diabetes Care. 2008;31(12):2383–2390. https://doi.org/10.2337/dc08-0985
3. Vancampfort D, Stubbs B, Mitchell AJ, De Hert M, Wampers M, Ward PB, et al. Risk of metabolic syndrome and its components in people with schizophrenia and related psychotic disorders, bipolar disorder and major depressive disorder: a systematic review and meta-analysis. World Psychiatry. 2015;14(3):339–347. https://doi.org/10.1002/wps.20252
4. Firth J, Marx W, Dash S, Carney R, Teasdale SB, Solmi M, et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosom Med. 2019;81(3):265–280. https://doi.org/10.1097/PSY.0000000000000673
5. Jacka FN, O’Neil A, Opie R, Itsiopoulos C, Cotton S, Mohebbi M, et al. A randomised controlled trial of dietary improvement for adults with major depression (the SMILES trial). BMC Med. 2017;15:23. https://doi.org/10.1186/s12916-017-0791-y
6. Sethi S, Wakeham D, Ketter T, Hooshmand F, Bjornstad J, Richards B, et al. Ketogenic diet intervention on metabolic and psychiatric health in bipolar and schizophrenia: a pilot trial. Psychiatry Res. 2024;335:115866. https://doi.org/10.1016/j.psychres.2024.115866
7. ClinicalTrials.gov. Ketogenic metabolic therapy in serious mental illness. NCT06748950. https://clinicaltrials.gov/study/NCT06748950
8. South African Depression and Anxiety Group. Helpline numbers. https://www.sadag.org/

Prepared by The Noakes Foundation team for public education. This article is not medical advice.