A team of scientists from Macquarie University in Australia have been examining the links between diet and depression. A small study asked a focus group to follow a diet with help and advice. A second group were given no intervention, simply asked to return after 3 weeks. The results of the study were published on an open access basis in PLOS One and can be read in full in the online journal.
The scientists recognised that adolescence and young adulthood were key points at which young people are more likely to experience depression. They also recognised that diets are changing and that young people were less likely to consume food high in fibre, was food prepared from scratch and eat the recommended daily guidelines of 5 portions of fruit and vegetables a day. Although some studies have shown a link between the quality of the diet and depression, there were few involving young people and adolescents and links between depression and diet were not focused on, except as a secondary outcome.
The study took place as a three week, parallel group which experienced an intervention to improve mood. The participants were students aged between 17-35, and were offered course credit or cash reimbursement as an incentive to take part. Blood tests were not conducted as planned. The participants had a score on the Depression sub scale with that of moderate or higher depression. They also scored higher on a Dietary Fat and Sugar Screener, which suggested a poor diet that did not follow healthy eating guidelines. Participants were allowed to take part if they had been on treatment for depression or psychological therapy for at least 2 weeks before starting the study. They also had their BMI checked, it was noted whether they were a smoker and whether they were currently taking medication, including for either medical or psychological health conditions.
The group who were in the Diet Change group, were given diet intervention instructions, via video from a registered dietician. They could rewatch the video online if needed. The advice given corresponded with the Australian Guide to Healthy Eating and included advice on a Mediterranean diet which as been linked to reduced risk of depression in other studies. Participants were to reduce their intake of refined carbohydrates, fatty or processed meats, sugar and soft drinks, while increasing their intake of fruit and vegetables to 5 a day, wholegrain cereals, unsweetened dairy, lean protein, fish, nuts, seeds, olive oil, spices linked with reducing depression such as cinnamon and turmeric .
The group were given a sample meal plan, recipes, troubleshooting solutions and a FAQs sheet. They were also given a small hamper of healthy food and could keep their shopping receipts to receive a $60 gift card as money for the food they had bought. They also had a 5 minute phone call on Days 7 and 14 to check that they had no problems following the diet. Participants in the other group did not receive any instructions regarding their diet and were just asked to come back after 3 weeks. They were not offered money or a hamper of food. After 3 months, the Diet Change group were given a phone call that checked up on how they were and whether they had continued to follow the diet.
The Diet Change group had significantly lowered their anxiety scale score and depression scale score on Day 21 when compared to the no change group. There were no significant differences between the groups for current mood assessment, but the Diet Change group seemed to score better on an anger scale. There were a similar amount of participants reporting a stressful event happening during the study in both groups. There were no significant changes to BMI, poor health or physical activity. The Diet Change group managed to change their diet for the three weeks, particularly reducing foods high in saturated fat and refined sugar. Some of the participants were followed up after three months and some had maintained the diet, while others had maintained only some aspects. 7 had not continued the diet at all. There was no difference in depression outcomes for these groups.
The study had some limitations: the small sample size and the fact that one group received inducements to continue the study while the other did not. The scientists noted that it would be better to even this out. They were pleased to find that it was possible to change the diet of this group of people, using low-cost intervention. The diet did not need following strictly to provide benefits to the participants. The scientists hoped that longer study periods could provide more benefits to participants in the future.
Francis, H.M., et al., A brief diet intervention can reduce symptoms of depression in young adults - A randomised controlled trial, PLOS One, October 2019