Although current evidence confirms the importance of diet for mental health, many psychologists avoid discussing dietary intake with clients, questioning whether this information is within their scope of practice. This article provides psychologists with a review focused on the connection between what we eat and how we feel. Eating a healthy, whole-foods-based diet is an important tool to promote mental health recovery and maintenance. We begin by reviewing several mechanisms by which nutrients maximize brain health, including enabling metabolic reactions to occur, supporting mitochondrial function, reducing inflammation and assisting with detoxification. Understanding the vital role of nutrients for brain health will aid clients in understanding the importance of optimizing their intake of a range of nutrients in order to maximize their mental health: no single nutrient is sufficient. Next, we summarize evidence relating diet to mental health, followed by a consideration of circumstances that may contribute to a client requiring additional nutrients, such as chronic stress, medication use, individual biochemistry, and consuming nutrientdepleted food. The evidence base for treating psychological problems in children with supplementary nutrients is then reviewed, and a case study of a child whose self-regulatory skills improved with broad-spectrum multinutrients is used to illustrate this treatment. The breadth and consistency of the research highlights the importance of children receiving a good foundation of nutrients for optimizing brain health. Finally, we offer practical suggestions for psychologists to incorporate this information into their clinical practice and discuss these suggestions within the context of informed consent.