The Relationship Between Nutrition and Mental Health: An Overview of Reviews

Background: The notion that nutrition or diet and mental well-being are associated is clearly embraced given the thousands of primary empirical studies that have examined this relationship. The literature has gone beyond simply examining nutrition as a risk factor to acknowledging nutrition as a target or lever for change that can be integrated into prevention or intervention approaches (e.g., Heilskov Rytter et al., 2015; Murakami & Sasaki, 2010; Sarris et al., 2012). Given the large amount of extant literature, many systematic reviews or meta-analyses exist: however, syntheses have explored nutrition as related to mental well-being almost exclusively within narrowly defined populations and often approach these issues from a discipline-specific perspective. Thus, although reviews highlight "high volume" research areas, they have not created a comprehensive picture of how nutrition may be leveraged to enhance prevention and intervention in real-world settings and across the lifespan.

Objective: This paper is a systematic review of reviews or overview (Cooper & Koenka, 2012) of the existing synthesis literature on the link between nutrition and mental well-being in primary studies. We aim to contribute to a more comprehensive understanding of the link between nutrition and mental well-being by exploring themes across multiple disciplines, populations, and interventions and to identify gaps in the research base.

Methods: We followed PRISMA guidelines (Liberati et al., 2009). We searched for articles in the psychology, health, and medicine fields in multiple electronic databases, reference lists, and journals. Studies were double-coded with a piloted coding tool and risk of bias was assessed for each review using the ROBIS tool (Whiting et al., 2015).

Results: Our electronic searches resulted in 157 non-duplicated articles screened at the abstract level and 33 from handsearches. Of the 99 articles reviewed in full text, 44 articles were eligible (systematic reviews, N = 32; meta-analyses, N = 15). Preliminary analyses indicate that reviews focused on a range of nutrition predictors including vitamin D (N = 7) and B6 (N=2), omega-3/ n-3 PUFAs (N = 9), iron and zinc (N=1), magnesium (N=1) and overall dietary patterns. Reviews also addressed a variety of mental health outcomes; however, the most prevalent was depression (N = 20). Some reviews also limited the sample to focus solely on women (N=2) or youth (N=4), although many focused on population-level studies of adults.

Discussion: Following a review of the characteristics and outcomes of the reviews, we will highlight strengths, gaps, and implications for practice, training for practitioners, and policy.