The authors of a meta-analysis of 41 previous studies into mental health and diet found such strong associations, including a likely causal link between diet and depression, that they recommend GPs discuss diet with patients. There was a robust association between both higher adherence to a Mediterranean diet and lower adherence to a pro-inflammatory diet and a lower risk of depression. Also they found that an extensive body of evidence now points to the microbiome-gut-brain axis as playing a key role in neuropsychiatry, and to the primacy of diet as a factor modulating this axis Lassale C, Batty GD, Baghdadli A et al. Healthy dietary indices and risk of depressive outcomes – a systematic review and meta-analysis of observational studies(external link)
People with some kind of mental health problem eat fewer healthy foods (such as fresh fruit and vegetables, organic foods and meals made from scratch) and more unhealthy foods (chips and crisps, chocolate, ready meals and takeaways). Diet and mental health(external link) Mental Health Foundation, UK
A diet high in refined sugars is related to poorer brain functioning and worsening mood disorders, such as depression. The risk of depression is 25% to 35% lower in those who eat a traditional diet high in vegetables, fruits, unprocessed grains, and fish and seafood, and only modest amounts of lean meats and dairy, an little or no processed and refined foods and sugars. Nutritional psychiatry – your brain on food(external link) Harvard Health, US, 2015
Long-term exposure to unhealthy dietary habits independently predisposes someone to depression over the life course, regardless of socioeconomic circumstances and other health behaviours. Jacka FN, Cherbuin N, Anstey KJ, Butterworth P. Dietary patterns and depressive symptoms over time: examining the relationships with socioeconomic position, health behaviours and cardiovascular risk(external link) PLoS One. 2014 Jan 29;9(1):e87657
People with better quality diets are less likely to be depressed, whereas a higher intake of processed and unhealthy foods is associated with increased anxiety. Jacka FN, Mykletun A, Berk M, Bjelland I, Tell GS. The association between habitual diet quality and the common mental disorders in community-dwelling adults – the Hordaland Health study(external link) Psychosom Med. 2011 Jul-Aug;73(6):483–490.
Researchers into the relationship between unhealthy dietary patterns and poorer mental health in children and adolescents observed a consistent trend for the relationship between good-quality diet and better mental health. O’Neil A, Quirk SE, Housden S, et al. Relationship between diet and mental health in children and adolescents – a systematic review(external link) Am J Public Health. 2014 October; 104(10): e31–e42.
Further, appropriate diet helps reduce depression in older adults. Reynolds CF, Thomas SB, Morse JQ. Early intervention to preempt major depression in older black and white adults(external link) Psychiatr Serv. 2014 Jun 1; 65(6): 765–773.