Young men with a poor diet saw a significant improvement in their symptoms of depression when they switched to a healthy Mediterranean diet, a new study has found.
Depression is a common mental health condition that affects approximately 1 million Australians and one in five New Zealanders each year. It also affects one in eight males and is especially prevalent in young adults.
The 12-week trial, conducted by researchers from the University of Technology Sydney (UTS), was recently published in the peer-reviewed American Journal of Clinical Nutrition.
Lead researcher Jessica Bayes, a PhD candidate in the UTS Faculty of Health, said the study is the first randomised clinical trial to assess the impact of a Mediterranean diet on the symptoms of moderate to severe depression in young men, aged 18 to 25. A total of 72 participants completed the study.
In a randomised controlled trial, the subjects are randomly assigned to a test group, which receives the treatment, or a control group, which commonly receives a placebo. In 'blind' trials, participants do not know which group they are in; in 'double blind' trials, the experimenters do not know either. Blinding trials helps remove bias.
Those in the control group were assigned befriending therapy - an emotional supportive relationship in which one-to-one companionship is provided on a regular basis by a volunteer.
The results of the study found that compared to befriending, a Mediterranean diet led to decreases in the participants' scores on the Beck Depression Inventory Scale (BDI-II) - a self-report inventory designed to assess the presence and severity in depressive symptoms. The participants adhering to the diet also saw increases in their Quality of Life (QoL) scores, suggesting that a Mediterranean diet could be beneficial in treating depression, particularly during young adulthood - which offers an opportunity for early dietary interventions.
"These results highlight the important role of nutrition for the treatment of depression and should inform advice given by clinicians to this specific demographic population," the researchers concluded in their report.
Commenting on the findings, Bayes said the researchers were "surprised" by how willing the young men were to take on a new diet.
"Those assigned to the Mediterranean diet were able to significantly change their original diets, under the guidance of a nutritionist, over a short time frame," she said.
"It suggests that medical doctors and psychologists should consider referring depressed young men to a nutritionist or dietitian as an important component of treating clinical depression."
The study contributes to the emerging field of nutritional psychiatry, which aims to explore the effects that specific nutrients, foods and dietary patterns can have on mental health. The diet utilised in the study was rich in colourful vegetables, legumes and wholegrains, oily fish, olive oil and raw, unsalted nuts.
"The primary focus was on increasing diet quality with fresh wholefoods while reducing the intake of 'fast' foods, sugar and processed red meat," Bayes said.
"There are lots of reasons why scientifically we think food affects mood. For example, around 90 percent of serotonin, a chemical that helps us feel happy, is made in our gut by our gut microbes. There is emerging evidence that these microbes can communicate to the brain via the vagus nerve, in what is called the gut-brain axis.
"To have beneficial microbes, we need to feed them fibre, which is found in legumes, fruits and vegetables."
Roughly 30 percent of depressed patients fail to adequately respond to standard treatments for major depressive disorder, such as cognitive behaviour therapy and antidepressant medications, Bayes added.
"Nearly all our participants stayed with the programme, and many were keen to continue the diet once the study ended, which shows how effective, tolerable and worthwhile they found the intervention."
The Mediterranean diet is a diet inspired by the eating habits of people who live near the Mediterranean Sea, drawing on the cuisines of Greece, Turkey, Italy and Spain. The heart-healthy eating plan is plant-based and incorporates the traditional flavours and cooking methods of the region.
Interest in the diet began in the 1950s when it was noted that heart disease was not as common in Mediterranean countries as it was in the US. Since then, numerous studies have confirmed that the diet helps prevent heart disease and stroke.
Plant-based foods such as whole grains, vegetables, legumes, fruits, nuts, seeds, herbs and spices, are the foundation of the diet. Olive oil is the main source of added fat, while fish, seafood, dairy and poultry are included in moderation. Red meat and sweets are eaten occasionally.