In the first study of its type, researchers conclude that even a brief shift in dietary habits can alleviate the symptoms of depression in young adults. The findings offer hope, but more work is needed.
Science has now clearly established the impact of poor diet on overall physical health.
More recently, researchers have begun to focus on the impact of healthful or unhealthful eating on mental health.
In fact, as the authors of the latest study explain, diet is now considered a "modifiable risk factor for depression."
Although evidence is mounting, most of it is observational. In other words, currently, it is difficult to ascertain whether eating a healthful diet staves off depression or whether experiencing depression drives unhealthful eating habits.
Filling a gap
According to the authors, to date, only one randomized control trial has investigated a dietary intervention on adults with a clinical diagnosis of depression.
The 12-week study concluded that "dietary improvement may provide an efficacious and accessible treatment strategy for the management of [major depression]."
The latest study, appearing now in PLOS ONE, adds more flesh to the bones.
In this study, the scientists wanted to uncover whether young adults living with depression could benefit from a 3-week dietary intervention. At the same time, they were keen to know whether young people with depression would be able to stick to a dietary intervention.
The researchers chose to study young adults because, as they explain, "adolescence and young adulthood are a period where there is increased risk of depression, and these are also critical periods for establishing health patterns — such as diet — which will carry over into adulthood."
To investigate, researchers from Macquarie University in Australia recruited 76 participants between 17 and 35 years of age. All participants were experiencing moderate-to-high symptoms of depression, and their standard diet included high levels of sugar, saturated fats, and processed foods.
The dietary interventions
The scientists split the participants into two groups; the "diet change" group and the "regular diet" group.
The scientists gave the diet change group nutritional advice in the form of a 13-minute video, which they posted online for the student to reference during the study.
Members of this group received a small hamper of healthful food and the promise of a $60 gift card if they handed in their shopping receipts at the end of the study.
The diet change group also received two check-in calls during the study, on days 7 and 14. The "regular diet" group, however, received no dietary instructions, free food, or gift cards; the research team simply asked them to return after 3 weeks.
At the beginning and end of the 3-week study, all participants went through a battery of tests. The scientists assessed levels of depression, mood, and anxiety, and also tested learning and reasoning skills.
As hoped, participants in the experimental group did adhere to the dietary changes. In this diet change group, depression scores improved significantly. Both anxiety and stress scores also improved.
Conversely, the regular diet group experienced no significant changes in depression score.
After 3 months, the researchers spoke with 33 of the participants over the phone. Although only seven of these individuals were maintaining the healthful eating plan, the improvements in mood were still significant across this small group.
Overall, the authors conclude:
"Modifying diet to reduce processed food intake and increase consumption of fruit, vegetables, fish, and olive oil improved depression symptoms in young adults. These findings add to a growing literature showing a modest change to diet is a useful adjunct therapy to reduce symptoms of depression."
Limitations and challenges
Although the current findings add to the evidence that food plays a role in mental health, the study does have significant limitations.
First and foremost, the study only recruited a small number of participants; and these were exclusively young adults that were attending the university, so the findings might not apply to other demographics.
Importantly, individuals in the regular diet group received no guidance, no free food, and no cash incentive; this is a considerable issue. Future studies may want to attempt to match the two conditions more closely. For instance, both groups could receive the same financial reward and check-in calls.
As for the 3-month follow-up, the research team conducted this over the telephone with just 33 participants, so it is difficult to extrapolate the findings further.
Because the relationship between nutrition and mental health is a hot topic, other researchers are likely to publish similar studies thick and fast. Both nutrition and mental health are challenging to investigate alone, so examining the interaction between the two is more difficult still.
Developing a clear picture of the role of diet in psychological well-being is complex indeed. With that said, the links between eating well and mental health are already growing stronger.