- The SMILES trial is the first randomised controlled study in the world to demonstrate that making dietary changes can be effective in improving the mental health of individuals with clinically diagnosed depression.
- Trial participants who improved their diet the most experienced the greatest benefits to their depression. But, importantly, mental health benefits were also observed with small dietary changes.
- The results of this trial are very important in directing future research, as well as informing how we manage or treat some common mental disorders such as depression.
- Mental health disorders are the leading cause of disability and burden of disease globally.
- Diet quality is one of the key factors influencing mental and brain health across all stages of life.
A world-first randomised clinical trial
Clinical depression is a leading cause of disability globally, so Deakin researchers carried out a world-first study to show that improvement to diet can provide an economical solution to poor mental health.
According to the World Health Organisation (WHO), depression affects more than 264 million people of all ages around the world. While treatment traditionally focuses on biological and psychological causes, evidence from studies across different life cultures and life stages suggests that the quality of our diets is directly associated with our mental health.
Deakin University’s SMILES trial (Supporting the Modification of lifestyle In Lowered Emotional States) is the first randomised controlled trial to investigate the relationship between diet and mental health and confirms that a healthy diet could be effective in improving the mental health of people with clinical depression.
Before the SMILES trial, emerging evidence from observational studies showed that diet quality was associated with mental health. In these studies, higher intakes of fruit, vegetables, whole grains and fish, and lower intakes of highly processed and sugary foods were associated with better mental health outcomes.
While the modification of diet has been widely recognised and promoted in the primary prevention of other non-communicable diseases like heart disease, diabetes and obesity, the idea of diet as a key part of the treatment of mental disorders had not yet been studied.
As the first study of its kind in the world to ask the question, ‘if I improve my diet, will my mood improve?’ and the first randomised clinical trial to show that improvements to diet could help treat major depression, SMILES’ results offer an important new strategy for the treatment of depression and are important in informing and directing future research in the management of common mental disorders.
Turning a worrying global trend around
Mental disorders, particularly depression, account for the highest burden of global disability. But despite an increase in recognition and treatment, recent data from around the world suggests rates of mental illness may be growing, particularly in young people. According to Deakin’s Food and Mood Centre, a unique multi-disciplinary research centre, half of mental illnesses first develop before 14 years of age and childhood disorders can be linked to a range of long-term detrimental social, criminal and economic outcomes in adulthood.
‘Depression also increases the risk of (and, in turn, is also increased by) common physical illnesses such as obesity, type 2 diabetes and heart disease. Successfully improving the quality of patients’ diets would also benefit these illnesses,’ says Professor of Nutritional and Epidemiological Psychiatry and Food and Mood Centre Director Felice Jacka.
‘While approximately half of sufferers are helped by currently available medical and psychological therapies, new treatment options for depression are urgently needed.’
The SMILES trial has been highly impactful and extensively published internationally since trial completion in 2016. The findings have helped transform the dietary management of individuals with clinical depression and has been the foundation and cornerstone for all subsequent trials conducted at the Food and Mood Centre.
A new field of research
Trials at the Food and Mood Centre have shown that dietary intervention can improve depressive symptoms, leading to a new field of research: nutritional psychiatry.
Nutritional psychiatry explores risk factors and develops solutions to mental health problems using dietary and nutritional strategies.
Professor Jacka says diet isn’t the only cause of, or solution to depression, but diet could support the overall health and functioning of people, in addition to treating their depressive symptoms.
Participants in the SMILES trial who improved their diet the most experienced the greatest benefits to their depression. But, importantly, mental health benefits were also observed with small dietary changes.
‘Depression, like any other mental illness, has many causes and many drivers, but if we can identify things like diet that are relatively straightforward and cost-effective to address, then that should be underpinning all other strategies for prevention and treatment,’ Professor Jacka says.
Grants and Funding
This study was supported by a project grant from the National Health and Medical Research Council of Australia (NHMRC). Additionally, Woolworths Limited provided sponsorship in the form of food vouchers for participants, which allowed for delivery of two food hampers at baseline and trial completion. A grant from Meat and Livestock Australia (2013) funded biochemistry data collected and analysed as part of the SMILES trial. *
The SMILES trial was a research collaboration consisting of investigators and research staff from Deakin University, La Trobe University and the University of Melbourne.
Chief Investigators on the SMILES trial included: Professor Felice Jacka, Associate Professor Adrienne O’Neil, Professor David Castle, Dr Laima Brazionis, Professor Catherine Itsiopoulos, and Professor Michael Berk. The project team included a number of research assistants (RA) and PhD students, including, Dr Rachelle Opie (lead dietitian), Josephine Pizzinga (dietitian), Dr Sarah Dash (trial coordinator and RA), Melanie Ashton (trial coordinator and RA), and Laura Nicholls (RA).
The Food and Mood Centre provides people around the world with a new approach to promoting mental wellbeing through a good diet by offering a free online short course Food and Mood: Improving Mental Health Through Diet and Nutrition through Future Learn. As the world’s first free course in the field of nutritional psychiatry, it provides participants with the latest food and mood research, as well as information on how to optimise diets for better mental health.
* These sponsors had no role in the design, analysis or preparation of manuscripts for publication.