Study to improve nutrition in adults with severe depression

A randomized controlled trial to improve nutrition in adults with major depression (the ‘SMILES’ study)

What was the study about?

Using a randomized, controlled study design, the authors wanted to investigate the effectiveness of a program to improve nutrition in the treatment of severe depression.

In summary, this is the first RCT (randomized controlled trial) that explicitly attempts to answer the question: If I improve my diet, will my mental health improve? Although we emphasize the preliminary nature of this study and the need for replication in studies with larger samples, the results of our study suggest, that nutritional improvement guided by a clinical nutritionist could be an effective treatment strategy for the management of this highly prevalent mental disorder.

Results:

• After 12 weeks, 32.3% (n = 10) of the group with dietary support and 8.0% (n = 2) of the control group with social support achieved the remission criterion of a score of less than 10 on the MADRS; this difference between the groups was significant
• These significant differences remained even after controlling for gender, education, physical activity, baseline BMI and baseline ModiMedDiet scores.
• Based on these numbers, the diet support group had “greatly improved” scores on average, while the social support control group had “minimally improved” scores on the CGI-I
• At the end of the intervention, the dietary support group showed significant improvements in consumption of the following food groups: Whole grains (mean increase of 1.21 (SD 1.77) servings/day), fruit (0.46 (0.71) servings/day), dairy (0.52 (0.72) servings/day), olive oil (0.42 (0.49) servings/day), legumes (1.40 (2.39) servings/week) and fish (1.12 (2.65) servings/week).
• With regard to the consumption of unhealthy foods, the consumption of extras decreased significantly in the diet support group (mean decrease 21.76 (SD 16.01) portions/week). Conversely, in the control group with social support, no significant changes were observed for any of the main food groups.
• These results provide preliminary RCT evidence for improving diet as an effective treatment strategy for depressive episodes.
• We report a significant reduction in depression symptoms as a result of this intervention, with an overall effect size of -1.16. These effects appear to be independent of changes in BMI, self-efficacy, smoking rate and/or physical activity.
• Consistent with our primary outcome, significant improvements were also observed in self-reported depressive and anxiety symptoms and on the Clinical Global Impressions Improvement Scale. While other mood (POMS) and well-being (WHO-5) scores did not differ between groups, the changes were in the expected direction and were likely influenced by a lack of statistical power.
• Critically, significant improvements on the ModiMedDiet score were seen in the nutritional support group but not in the social support control group, and these changes correlated with the changes in MADRS scores.
• The results of this study suggest that improving diet according to current recommendations for the treatment of depression [31] may be a useful and accessible strategy for treating depression in both the general population and in clinical settings.
• One relevant observation was that the improvements in depressive symptoms were independent of the change in weight. These results were to be expected as the dietary intervention was ad libitum and not aimed at weight loss, but they are further support for the positive role of improving diet itself.
• There are many other biological pathways through which improving diet can influence depressive illness; previous discussions have focused on inflammatory [18] and oxidative stress pathways [19] and brain plasticity [16] and the new evidence base focuses on the gut microbiota [17]. Each of these pathways is thought to play a role in depression and is also influenced by the quality of the diet. In addition, behavioral changes related to eating (cooking/cooking/meals) are an expected outcome of a nutritional intervention, and these changes in activity may also have had a therapeutic benefit.
• However, there is evidence that our study sample did not necessarily represent a particular subgroup; the recent 2014-2015 Australian Health Survey shows that only 5.6% of Australian adults had an adequate intake of vegetables and fruit. In this study, only 15 out of 166 people studied were excluded due to a pre-existing ‘good’ diet, suggesting that – in line with the wider population – a poor diet is the norm in people with a depressive illness.
• In summary, this is the first RCT that explicitly attempts to answer the question: If I improve my diet, will my mental health improve? Although we emphasize the preliminary nature of this study and the need for replication in studies with larger samples, the results of our study suggest, that nutritional improvement guided by a clinical nutritionist could be an effective treatment strategy for the management of this highly prevalent mental disorder.

The two groups studied were

1. the intervention group:

• The dietary intervention included personalized nutritional counseling and support from a clinical dietitian, including motivational interviewing, goal setting, and mindful eating to support optimal adherence to the recommended diet.
• The primary focus was on increasing the quality of nutrition by supporting the consumption of the following 12 main food groups (recommended portions in brackets): Whole grain products (5-8 portions per day); Vegetables (6 per day); Fruit (3 per day), Pulses (3-4 per week); low-fat and unsweetened dairy products (2-3 per day); raw and unsalted nuts (1 per day); Fish (at least 2 per week); lean red meat (3-4 per week) [32]chicken (2-3 per week); eggs (up to 6 per week); and olive oil (3 tablespoons per day), while reducing the intake of “extras” such as sweets, refined grains, fried foods, fast food, processed meats and sugary drinks (no more than 3 per week). The consumption of red or white wine in excess of 2 standard drinks per day and all other alcohol (e.g. spirits, beer) were included in the group of “extras”.
• The participants were advised to consume the diet ad libitum, as the intervention was not aimed at weight loss.
• The participants received seven individual nutritional counseling sessions, each lasting approximately 60 minutes, conducted by a registered dietitian; the first four sessions took place weekly, the remaining three sessions every two weeks.
• Participants received supporting written information specifically designed for the intervention to support adherence to the diet.
• To provide examples of portion sizes and how to handle the recommended foods, participants also received a food basket with the main components of the diet, as well as recipes and meal plans.
• Motivational interviewing techniques were used in the following sessions and participants were encouraged to set personal goals.

2. The group with social support

• The social support control condition included a manualized “befriending” protocol [26], which used the same visit schedule and duration as the nutritional support intervention.
• Befriending consists of trained staff discussing neutral topics of interest to the participant, such as sports, news or music, or in cases where participants find the conversation difficult, offering alternative activities such as card or board games, with the intention of keeping the participant engaged and positive.
• Befriending aims to control four factors: Time, client expectancy, therapeutic alliance and therapist factors compared to the intervention group in an RCT and is often used as a control condition for clinical trials of psychotherapy