A 6-month randomised controlled trial investigating effects of Mediterranean-style diet and fish oil supplementation on dietary behaviour change, mental and cardiometabolic health and health-related quality of life in adults with depression (HELFIMED): Study protocol

Modern diets, characterised by excess consumption of processed foods, are accompanied by an epidemic of chronic diseases. Cardiovascular disease and depression carry large burden of disease, and overlap with each other. Poor dietary patterns have been identified as an independent risk factor for depression while healthy diets are protective. Traditional Mediterranean diets have been shown to reduce risk of cardiovascular disease; however there is a need for clinical trials in people with depression. This study reports the protocol and 3-month dietary outcomes of a Mediterranean-style diet randomised controlled trial (RCT) conducted in adults with self-reported depression. Methods: HELFIMED is a parallel 6-month RCT investigating whether dietary patterns can be improved in people with depressive symptoms and whether healthier diet combined with fish oil supplementation can improve mental and cardiometabolic health and quality of life. Adults aged 18-65 with self-reported depressive symptoms (N=164) were block-randomised on age and gender between May 2014 to June 2015 to receive nutrition education, food hampers fortnightly cooking workshops based on Mediterranean-style dietary principles for 3 months and fish oil supplementation for 6 months, or to attend fortnightly social groups (control group) for 3 months. All participants completed mental health, quality of life and dietary questionnaires and provided anthropometric measurements, blood and urine samples at baseline, 3 and 6 months. Dietary changes: Compared to the control group (n=44) at 3 months the treatment group (n=60) reported a higher Mediterranean diet score (P<0.001), consumed more vegetables (P=0.002), wholegrains (P=0.040), nuts (P=0.028), legumes (p=0.029) and fish (p=0.020), greater diversity of vegetables (p=0.001) and less takeaway food (p=0.070), unhealthy snacks (p=0.061) and meat/chicken (p=0.005). Discussion: Over 3-months this intervention improved dietary patterns of adults suffering depressive symptoms and may provide a useful protocol for sustainable dietary change. Sustainability of dietary changes will be assessed at 6 months. Further analyses using linear mixed modelling and regression analysis will investigate the effects of dietary changes and fish oil supplementation on mental and cardiometabolic health and quality of life.