Eating for Better Mental Health

How the revolutionary SMILES trial at Deakin University is changing the way we look at supporting mental health.

By Dr. Tetyana Rocks

The Mediterranean-style diet isn’t just about enjoying delicious dishes; evidence suggests it's also one of the proven ways to support and improve physical and mental wellbeing. Following this diet has been associated with numerous health benefits, including decreased risks of cardiovascular disease and cancer, reduced cognitive decline, and fewer depressive symptoms. 

Observational evidence shows that adopting a Mediterranean way of eating, rich in various plant foods like vegetables, fruits, grains, legumes, nuts, and seeds, while limiting ultra-processed "Western" foods, is linked to better mental health and reduced risk of mental health issues across different cultures and life stages. 

What is even more exiting, research studies have demonstrated that changing our eating habits and improving diet quality can also improve mental health outcomes! The SMILES trial, led by Prof Felice Jacka and conducted at Deakin University's Food & Mood Centre in Australia, was the first randomized controlled trial to show that dietary changes can effectively improve mental health in people with depression. 

In the SMILES trial, participants diagnosed with moderate to severe major depressive disorder and poor dietary habits were randomly assigned to two groups: 

  1. Dietary support group (33 participants): Received personalized dietary recommendations based on the modified Mediterranean diet through regular consultations with a trained dietitian. 
  2. Social support group (34 participants): Received social support through a befriending protocol involving regular meetings with trained personnel to discuss interests and engage in activities like sports or music. 

Both groups had equal numbers of visits of the same duration and intensity, with outcomes assessed at baseline and after 12 weeks. 

The SMILES diet was developed based on findings from the PREDIMED study that showed a significant metabolic health benefits of Mediterranean way of eating. It closely resembled traditional Mediterranean diets in terms of macro- and micronutrient content. 

Consisting of 12 food groups with recommended proportions depicted in a pyramid diagram, the SMILES diet aimed to provide around 11,000 kJ (approximately 2,600 kcal) per day, with moderate amounts of protein and carbohydrates, and a relatively high fat content, primarily from monounsaturated fats in olive oil. Alcohol intake was limited to 2%, mainly from red wine. With a focus on high fibre intake from vegetables and fruits, the diet provided over 50g of fibre daily and met most recommended nutrient intakes for adults while ensuring satiety, with restrictions mainly on ultra-processed, salty, or sugary foods. 

After 12 weeks, results showed that the dietary support group experienced significantly greater improvements in mental health compared to the social support group, with 32% achieving full remission from depression. Participants who improved their diets the most also experienced the greatest reduction in depressive symptoms. Notably, there was no significant weight change in either group, as the focus was on improving nutritional quality rather than weight loss. 

Following the SMILES trial, several other studies in Australia and internationally have shown similar outcomes: improving diet quality by regularly eating a Mediterranean-style diet leads to significant improvements in depression-related outcomes. 

smiles diagram

Diagram. The SMILES trial food diagram. Adapted from Opie et al. 2017. @Deakin University.