Alex Schubert from the European College of Neuropsychopharmacology (ECNP) explores the link between our mental health and what we eat
Every day we consume a wide variety of substances with the specific goal of modifying our mental states. These can range from substances that are overtly mood-altering, such as coffee and alcohol, to those of a more diffuse impact, such as chocolate and folic acid, to out-and-out comfort foods, whose effects – like Proust’s famous madeleine moments – are less chemical than they are sentimental. We all instinctively know there is a connection between what we eat and how we feel, but as the madeleine moments show, that connection is multi-layered and maddeningly elusive. Its scientific basis, not altogether surprisingly, is also very poorly understood.
Nevertheless, we are finding out more and more. Research is revealing suggestive linkages, giving rise to a dynamic new field, ‘nutritional psychiatry,’ which is trying to unpick the complex web of interactions that connect what we eat with what we feel and how we behave.
Chair of the European College of Neuropsychopharmacology’s Nutrition Network Suzanne L. Dickson, professor of neurobiology at the University of Gothenburg, Sweden, explains what is at stake: “There’s a lot of accumulated wisdom about how nutrition meshes with brain health, but not much hard science. In particular, what we’re missing is a means to connect the many insights we’ve acquired on food’s effects to the underlying neurobiology and, in doing so, develop a path that might lead one day to actual nutrition-based treatments.
“The promise of nutritional psychiatry is that by identifying which nutritional components truly matter for brain health and how these interact with the body’s metabolic, endocrine and other signalling processes, we can work out how to modulate neuronal function and, in turn, influence behaviour.
“We’re only at the beginning, but if we can isolate the environmental, lifestyle and genetic factors that determine nutritional responses, bearing in mind that humans are very different in the food they eat and how they process it, we can begin to envisage a future of personalised nutrition.”
The importance of food for the brain’s functioning is easily inferred from how the brain works. Maintaining its composition, structure and synaptic function relies on access to the appropriate nutrients, including lipids, amino acids, vitamins and minerals. These can only be obtained in the quantities we need them through the intake of nutrients in the food we eat.
Moreover, endogenous gut hormones, neurotransmitters and the gut microbiota-derived substances that mediate brain-gut-microbiota communication are directly affected by the composition of our diets. The implications are very important: if, as it appears, food intake and food quality have a direct impact on brain function, by modifying that intake we have the potential to influence cognitive performance and overall brain health.
We already have many interesting leads. Mounting evidence points to a healthy diet, rich in polyphenols, B-vitamins, polyunsaturated fatty acids and nutritional supplements, having a positive influence on mental health, cognitive performance and stress reactivity. There are reasons to believe, for example, that omega-3 polyunsaturated fatty acids can improve cognition and ameliorate anxiety and that dietary omega-3 polyunsaturated fatty acids supplementation protects against the development of cognitive impairment, hyperactivity of the hypothalamic- pituitary-adrenal (HPA) axis and neuro-inflammation. Dietary exposure to high levels of polyphenols, B-vitamins and polyunsaturated fatty acids during middle age has also been found to correlate with better cognitive performance later in life. A recent study has even suggested that plasma monounsaturated fatty acids can significantly influence the efficiency of functional connectivity in the brain and enhance general intelligence.
We also have a large body of epidemiological evidence that points strongly to the influence of diet on mental function and brain health. Early life malnutrition studies show that proper nutrition is essential for brain development in childhood and that these effects carry through right into adulthood and old age. At any stage of life, in fact, an improved diet quality is associated with better cognitive fitness and reduced risk of cognitive decline. Not only has the intake of antioxidant polyphenols been linked to improved cognitive abilities in the elderly, but higher serum vitamin D concentrations have been shown to be closely associated with better attention and working memory performance in the over-65s, pointing to a frontline role for diet in the fight against cognitive decline. For an ageing population facing rising levels of neurodegenerative dysfunction, these are very encouraging findings.
New evidence has also brought to light the role that the intestinal microbiome plays in the development and functioning of the brain, with data showing that the gut microbiota is critically implicated in the body’s ability to manage stress and respond to affective disorders, such as anxiety and depression. The way stress can negatively affect the gut microbiota and digestive health opens up the promising possibility that stress might also be lessened if the gut microbiota can be appropriately regulated via a precision diet. While not minimising the impact of other complex determinants, including genetics, environment, lifestyle and mode of delivery, the close association between diet, nutrition, the digestive organs and mental health promises whole new lines of possible treatment research.
Yet, while compelling links between diet and brain health abound, identifying causes is another matter. “The evidence is pretty clear: nutrition, stress susceptibility, brain health and mental function are somehow bound up together,” says Suzanne Dickson. “But the evidence is correlational. There is a gap in understanding how these effects come about. What’s needed now are much more robust intervention studies in large cohorts to identify exactly which mechanisms are involved in connecting nutrition and neuronal functioning and how these mechanisms can be manipulated by improved dietary habits to enhance people’s mental health”.
This was the rationale behind the ECNP Nutrition Network, to pool European expertise in nutrition and neuroscience and help give nutritional psychiatry a more secure, evidence-based grounding. The Network includes researchers from academia as well as Europe’s leading food companies, attracted by the enormous therapeutic potential inherent in the field. “The long-term possibilities are immense,” says Dickson.
“Simply by adjusting what we eat we are looking at being able to lift general standards of health and wellbeing and reduce the growing social and economic cost of mental illness. Right now, it’s one of the most exciting areas of mental health research. We are very optimistic”.
Alex Schubert, Ph.D. - Nutritional Psychiatry