A diet rich in fruits, vegetables, whole grains, nuts, and fish—and low in processed foods (known as the Mediterranean diet) has been repeatedly suggested to have a positive effect on physical health, mental health, and quality of life (QoL). Now, a new randomized controlled trial has demonstrated that effect yet again for people with depression. The researchers found that depression scores and quality of life were both improved in a group with this diet when compared to a group receiving only social supports.
According to the researchers, “Higher Mediterranean diet scores were significantly associated with lower depression, anxiety, negative affect and better coping and overall QoL.”
These findings are consistent with another study published this year, which found that the Mediterranean diet resulted in remission of depressive symptoms in about 33% of participants—compared to only 8% of the control group. Another study this year suggested that nutritional deficiencies could be related to psychotic experiences as well.
The current analysis was led by researchers at the Centre for Population Health Research, University of South Australia, and included two groups. One group, the MedDiet group, received workshops focused on nutritional education and cooking skills, and were given ingredients, recipes, and fish oil supplements. The other group received social support get-togethers throughout the intervention, instead of nutritional support.
As expected, both groups demonstrated improvements on all measures, including depression and quality of life. After all, social support has been shown to be effective for both reducing depression and for increasing quality of life. However, the nutritional intervention had an effect above and beyond the social support component.
According to the researchers, “The MedDiet group reported significantly greater improvements in depression and overall mental health-related QoL compared to the social group. Improvements in a range of mental health outcomes were significantly correlated with improvements in diet over 3 months.”
The researchers found “60% fewer persons experiencing extremely severe levels of depression, 72% of anxiety and 69% of stress in the MedDiet group” than in the social support group.
The intervention lasted for three months, but the improvements appeared to persist over time. Reduced depression scores and improved quality of life scores remained after six months.
Another benefit of the Mediterranean diet is that it reduces risk of cardiovascular disease (CVD). People with mental health diagnoses are more likely to experience CVD, which may be at least partially due to psychiatric medications. A dietary intervention like this could improve symptoms and improve cardiovascular functioning at the same time.
In the study, the DASS questionnaire was used to determine levels of depression, anxiety, and stress, while quality of life was measured using the AQoL-8D. This measure includes eight factors, including independent living, pain, senses, happiness, self-worth, coping, relationships, and mental health. The PANAS questionnaire was used to measure positive and negative emotional states.
One limitation of the study was its large drop-out rate. 152 participants began the study, but only 95 were available at three-month follow-up, and 85 completed six-month follow-up. The researchers noted that many of the participants in the social support control group were disappointed that they did not receive the nutritional intervention, so drop-out was higher in that group.
The researchers put these findings in the context of the food habits of Western cultures.
“Westernized societies have developed an alarming culture of increased takeaway and ultra-processed food consumption which not only has dire health consequences but has also removed people from enjoying the whole process of growing, cooking, and enjoying good wholesome food together. With the increased personal, societal and financial burden of chronic physical and mental illness, getting back to basics by promoting cooking skills and family/group meals could be such a simple yet powerful and empowering approach to healthcare and prevention.”
Parletta, N., Zarnowiecki, D., Cho, J., Wilson, A., Bogomolova, S., Villani, A. . . . O’Dea, K. (2017). A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional Neuroscience, 1-14. https://doi.org/10.1080/1028415X.2017.1411320 (Link)