"The literature now strongly suggests that poor diet quality is associated with an increased risk of depression," the study said. "Diet is therefore a modifiable risk factor for depression, which would be a good target for early intervention."
While past research has focused on observing people’s diets and their moods, this study used randomized controlled trials where people are put into groups and one group receives an intervention.
The design allowed researchers to link changes to the controlled intervention. However, since the controlled group received significant attention, that factor might have also contributed to an alleviation of depression.
Still, the young adults’ ability to stick to the diet shows us that it wasn’t just additional support that led to benefits.
Some 17.3 million adults suffered from depression in 2017, and the age group with the most cases of depression were adults between 18 to 25, according to the National Institutes of Mental Health.
The study recruited adults with depression with an average age of 19. Half of the adults received dietary guidance from a registered dietician via an instructional video and were told to eat a modified Mediterranean-style diet with increased servings of vegetables, fruits, wholegrain cereals, protein, unsweetened dairy, fish, nuts and seeds, olive oil, and spices. They were instructed to decrease their consumption of refined carbohydrates, sugar, fatty or processed meats and soft drinks.
The group received sample meal plans and recipes, a small hamper of food items and were reimbursed up to $60 for grocery costs. During the three weeks of the study, they received two phone calls to check in and see how their diets were going.
The other half of the adults with depression received nothing and maintained their usual diet.
Three weeks later, researchers evaluated the depression of all subjects. They also checked that the group on the diet stuck to it by asking all the young adults about their eating patterns. Researchers kept them honest by using a special device that measures the levels of chemicals originating from fruits and vegetables in the skin.
The group that received dietary guidance had a healthier diet and reported feeling less depressed. When researchers checked in with some of them three months later, the benefits were still present in some of them.
Michelle Milgrim, a registered dietician and the manager of employee wellness at Northwell Health in New York, noted that a good diet can be helpful through a couple of potential mechanisms.
“Serotonin helps us control our mood. Anti-inflammatory diets – made up of high antioxidant foods like vegetables, beans, nuts and fruit as well as few refined sugars – protect the brain from oxidative damage,” she said.
Dr. Timothy Kreider, assistant professor of psychiatry at the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, who specializes in treating adults in this age group, said that diet may complement treatment with therapy and medication.
“Indirectly, a healthful diet makes you feel more energetic. More energy will increase your social and physical activity, and being more active is a key step in recovering from depression,” he said.
“Do we know what specific diet will treat depression? No, I don’t think we have solid evidence for that yet, but I’d love to see some," Kreider said.
Dr. Saumya Bhutani is a resident in psychiatry in New York working with the ABC News Medical Unit.