Efficacy of a Culturally-adapted Mediterranean Diet Intervention on Depression in Relation to the Gut Microbiome

Efficacy of a Culturally-adapted Mediterranean Diet Intervention on Depression in Relation to the Gut Microbiome: A Randomised Controlled Trial Using the Experience Sampling Methodology

The objective of this study is to investigate the efficacy of a culturally-adapted Mediterranean diet, in accordance with clinical guidelines and research evidence, in reducing depressive symptoms among Hong Kong Chinese adults. Additionally, this study will also explore the potential underlying role of the gut microbiome in the relationship between the Mediterranean diet and depression. This study serves as a pioneering attempt to examine the efficacy and intervention acceptability of a culturally-adapted Mediterranean diet in managing depressive symptoms.

Several studies have demonstrated the relationship between diet and mood, while existing studies suggest that consistently adhering to the Mediterranean diet may yield a more pronounced antidepressant effect. Considering that depression is often associated with low motivation, dietary interventions that require active participation may encounter implementation challenges and potentially impact the adherence rate. To address this issue, our study proposes using ecological momentary assessment (EMA), which involves sending frequent reminders to participants, allowing us to examine diet quality and adherence as well as changes in depressive symptoms at various time points. This approach also minimizes potential recall bias and enhances data collection accuracy. If the hypothesis is supported, dietary intervention could emerge as a promising therapeutic strategy for alleviating depressive symptoms. Furthermore, this study could provide insights into the role of the gut microbiome as a potential underlying mechanism between diet and depressive symptoms. The findings could have significant implications for clinical practice.

Inclusion Criteria:

1. Hong Kong residents aged 18-65 years;
2. Able to read Chinese and type in Chinese or English;
3. Have a Patient Health Questionnaire-9 (PHQ-9) score of 10 or higher, indicating at least a moderate level of depressive symptoms;
4. Meet the Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic criteria for current MDD according to the Mini International Neuropsychiatric Interview (MINI);
5. Have a Mediterranean Diet Index (KIDMED 2.0) score less than 3, indicating very-low-quality diet;
6. Possess an Internet-enabled iOS- or Android-operated mobile device; and
7. Willing to provide informed consent and comply with the trial protocol.

Exclusion Criteria:

1. The presence of other current psychiatric disorders as assessed by the MINI (bipolar disorder, posttraumatic stress disorder, personality disorders, eating disorders, psychotic disorders, or substance abuse disorder);
2. Have a medical condition or neurocognitive disorder that may prevent dietary changes as recommended by physicians or dietitians;
3. Current serious suicidal risk (non-fleeting intent or plan) as assessed by a PHQ-9 Item 9 score >2 (referral information to professional mental health services will be provided);
4. Involvement in dietary changes (self-initiated/supervised by professionals) in the past 2 weeks;
5. Involvement in any psychological treatment specifically for depression in the past 6 months;
6. A change in medication within 2 weeks prior to the baseline assessment/during the study;
7. Pregnancy and hospitalization;
8. Current participation in any other trial(s); and
9. Unwilling to change their diet if being allocated to the MediDiet group or food allergies or intolerances preventing diet adherence (specifically allergies to seafood, soy, nuts, yogurt, or dairy products).