Nutritional medicine as mainstream in psychiatry

Summary

Psychiatry is at an important juncture, with the current pharmacologically focused model having achieved modest benefits in addressing the burden of poor mental health worldwide. Although the determinants of mental health are complex, the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology. Evidence is steadily growing for the relation between dietary quality (and potential nutritional deficiencies) and mental health, and for the select use of nutrient-based supplements to address deficiencies, or as monotherapies or augmentation therapies. We present a viewpoint from an international collaboration of academics (members of the International Society for Nutritional Psychiatry Research), in which we provide a context and overview of the current evidence in this emerging field of research, and discuss the future direction. We advocate recognition of diet and nutrition as central determinants of both physical and mental health.

Introduction

Pharmacologically focused approaches have achieved a moderate reduction in the worldwide burden of poor mental health; however, indicators suggest that the burden of disease attributable to mental disorders will continue to rise worldwide during the coming decades.1, 2 Mental disorders in general, and major depression and anxiety disorders in particular, account for a large burden of disability worldwide.² Rapid urbanisation, and an overall transition from traditional lifestyles (concerning diet, physical activity, and social structures), which are some of the most pressing global and environmental issues of our time, have both been linked to increases in depression and other mental disorders.³ Indisputably, depression and other common mental disorders are already, and will probably become increasingly, part of an epidemic of comorbidity between physical and mental ill-health, with diet being a crucial common determinant.⁴

The current state, wherein populations in both developed and emerging economies preferentially consume nutrient-poor, energy-dense, highly processed foods, is historically unique—many people are both overfed and undernourished. Although caloric intake has increased, many individuals in affluent, developed nations do not meet the recommended intakes of several brain-essential nutrients, including B-group vitamins, zinc, and magnesium.⁵ Although slight improvements have been detected in the dietary intakes of sugar and fats between 2003–04 and 2009–10, documented intakes of nutrient-rich and fibre-rich vegetables and whole grains are far lower than recommended.⁶ These profound changes in dietary habits, along with tobacco use, insufficient physical activity, and harmful alcohol and recreational drug use, have resulted in an epidemic of ill health. The major non-communicable diseases, along with mental disorders, are expected to cost the worldwide economy US$47 trillion from 2014 to 2020, if no substantial and effective action is taken.⁷

A traditional whole-food diet, consisting of higher intakes of foods such as vegetables, fruits, seafood, whole grains, lean meat, nuts, and legumes, with avoidance of processed foods, is more likely to provide the nutrients that afford resiliency against the pathogenesis of mental disorders. The mechanisms by which nutrition might affect mental health are, at least superficially, quite obvious: the human brain operates at a very high metabolic rate, and uses a substantial proportion of total energy and nutrient intake; in both structure and function (including intracellular and intercellular communication), it is reliant on aminoacids, fats, vitamins, and minerals or trace elements.3, 8 Dietary habits modulate the functioning of the immune system, which also moderates the risk for depression.⁸ The antioxidant defence system, which is also implicated in mental disorders, operates with the support of nutrient cofactors and phytochemicals. Additionally, neurotrophic factors make essential contributions to neuronal plasticity and repair mechanisms throughout life, and these too are affected by nutritional factors.⁹

The purpose of this Personal View is to provide a platform for robust debate in the specialty, particularly regarding the need to move towards a new integrated framework in psychiatry, whereby consideration of nutritional factors should be standard practice. To provide a well informed and respected consensus statement¹⁰ and viewpoint on this position, we formed an international collaboration of academic authors from members of the International Society for Nutritional Psychiatry Research (ISNPR). In this Personal View, we outline the supportive evidence underpinning the proposed paradigm shift, and present our perspective about the future direction of nutritional medicine in psychiatry.