By Carolyn Crist

(Reuters Health) – Young adults who eat poorly and feel blue might be able to perk themselves up by switching to a healthier diet, a small study suggests.

In a randomized trial, men and women aged 17-35 in Australia who switched to a healthier diet had fewer depression symptoms after three weeks. And those who kept up the healthy eating for three months continued to feel better than at the start, researchers report in the journal PLoS ONE.

“This has 100% reach (since everybody needs to eat), is more cost effective than medications, and is an aspect of treatment that individuals can control themselves,” said lead study author Heather Francis of Macquarie University in Sydney, Australia.

“This raises the possibility that making changes to diet can act as a therapy to improve depression symptoms,” she told Reuters Health by email.

Francis and colleagues studied 76 people who scored high on two depression and anxiety scales – indicating moderate or high depression symptoms – and who also scored high on a questionnaire about dietary fat and sugar consumption.

Participants were randomly assigned to a diet-change group or a habitual-diet group for three weeks. The diet-change group received instructions from a registered dietician through a 13-minute video, which they could re-watch as needed. The video provided dietary guidance based on the 2003 Australian Guide to Healthy Eating as well as the Mediterranean Diet eating pattern. This included instructions to increase intake of vegetables to five servings per day, fruits to two or three servings per day, whole grains to three servings per day, lean protein to three servings per day, unsweetened dairy to three servings per day and fish to three servings per week.

The program also recommended daily consumption of three tablespoons of nuts and seeds, two tablespoons of olive oil, and one teaspoon each of turmeric and cinnamon. Participants were also told to decrease refined carbohydrates, sugars, fatty or processed meats and soft drinks.

The diet-change group also received sample meal plans and recipes, as well as a box of food items, including olive oil, natural nut butter, walnuts, almonds, sunflower seeds, cinnamon and turmeric. They were told to keep their shopping receipts to be reimbursed with a $60 gift card.

After three weeks, average depression scores had dropped into the normal range in the diet-change group, while remaining elevated or severe in the habitual-diet group – and the improvements were maintained three months later, the research team reports.

“Depression is a whole-body disorder, not just a disorder of the brain,” Francis said. “Depression is associated with a chronic inflammatory response, but what is the source of this inflammation? (Earlier research has shown) that poor diet both increases systemic inflammation and is also a risk factor for depression.”

Still, researchers should be careful about suggesting cause-and-effect relationships in studies like these, said Marc Molendijk of Leiden University in The Netherlands, who wasn’t involved in the research.

Molendijk, who studies dietary habits and mental health and also serves on the PLoS ONE editorial board, cautioned against giving the results too much weight.

“There probably are expectancy effects at play, leading to a placebo effect,” he said by email. “It’s also a bad message to depressed people, as they may attribute the responsibility for their depression to themselves.”

On the other hand, noted Joseph Firth of the University of Manchester in the UK, “the age-old saying, ‘Healthy body, healthy mind’ really is true.”

Firth, who also wasn’t involved in the study, told Reuters Health by email, “No secret formula or complicated diets are required. Even simple positive behaviors such as eating healthier and being more active have notable benefits.”

SOURCE: PLoS ONE, online October 9, 2019.