Eat well and feel better…studies linking poor diet with depression

Sharon Craggs

Nov 18, 2019

Science 3


It is widely known that eating well has many health benefits; while a poor quality diet high in processed foods, saturated fats and refined sugars is associated with disorders such as heart disease, obesity and type 2 diabetes. Despite this, our busy lifestyles have led to a greater consumption of convenience foods lacking the necessary nutrients for good health.

Furthermore, a number of studies have found poor diet can also affect a person’s mental health. In 2017, a 12-week study on adults with moderate to severe depression was performed. This randomised controlled trial enrolled 67 adults who were split into two groups and received either dietary support or social support. Mental states were assessed before and after intervention, and to be eligible to participate the adults were judged to be eating a poor diet. This was defined as a low intake of dietary fibre, lean proteins and fruit and vegetables, and a high intake of sugar, processed meats and salty snacks.

The dietary support group received advice and support sessions to assist with improving the quality of their diet, including a hamper containing the recommended food groups and recipes. The social support (control) group had an equal number of support sessions, however these consisted of ‘befriending’ where the participant would interact with trained personnel in positive, but neutral, conversation or activities. The participants, who had mean age of 40 years old, were found to show statistically significant improvements in mood after diet intervention, compared to the control group.(1)

The Studies

A 2019 study found diet interventions can also reduce depression in young adults. A randomised controlled trial was performed on undergraduate students consuming a poor diet while presenting depressive symptoms. This 3-week study separated the participants into a diet change group or a habitual diet control group. The control group carried on eating as normal, the diet change group were instructed on changes to their diet and reimbursed the cost of study foods. Some additional guidance was given to this group to ensure adherence over the 3 weeks. Symptoms were measured in the 76 young adults taking part, and again there were significant improvements in mood for the diet change group compared to the habitual diet control group.(2)

The Results

The results of both these studies suggested that depressed individuals were not only capable of following and adhering to a diet plan, but these changes in diet could lead to a significant reduction in depressive symptoms. The recommended diet in both studies was based on a Mediterranean-style diet with increased servings of fruit, vegetables, unsweetened-dairy, nuts and seeds, proteins including lean meats, wholegrain cereals and fish. Also recommended was olive oil and spices such as turmeric and cinnamon for brain function. Participants were instructed to reduce processed and fried foods and sugary snacks and drinks. Despite the relatively small sample sizes in these two studies, there is a growing evidence that diet, as well as other lifestyle factors can impact on mood disorders. Hence, dietary improvements could be utilised by health professionals as an additional tool to treat this common but distressing illness.

Contact Sharon Craggs, our Technical Analyst for more information

References and
further reading:

  • Jacka, F.N. et al (2017) A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med. 2017; 15: 23. PMID: 28137247
  • Francis, H.M. et al (2019) A brief diet intervention can reduce symptoms of depression in young adults – A randomised controlled trial. PLoS ONE 14(10): e0222768. PMID: 31596866
Depression and Healthy Eating