By Dr Jocelyn Eason, general manager of Food Innovation for Plant and Food Research
The effect of diet on physical health is well known. Recently, scientists have also started uncovering the links between diet and mental states like anxiety and depression.
The gut has a vast number of serotonin receptors (serotonin is the neurotransmitter targeted in depression) among other things, which has led to approaches like ‘nutritional psychiatry’.
Until recently, the focus has mainly been on the role that foods might play in supporting mood via enhancing neurotransmitters or supporting brain function (omega-3 fatty acids, for example). Ongoing research is likely to reveal more about which specific foods influence varied mood states.
In the past decade, there has been lots of discussion around the importance of the enteric nervous system (sometimes called the ‘second brain’) and its two-way highway with the brain. This gut-brain axis and the anatomical, physiological and biochemical pathways via which food affects mood, are a recent focus of scientific study. This will expand our knowledge of how food, digestion and microbiome combine to influence brain and behaviour.
The gut is a dense and complex ‘ecosystem’. While microbiome species diversity is a marker of health, research is yet to understand what creates an optimum microbiome. Dietary choices – for example, fibre-rich plant foods that support gut health – are likely to play an important role. On the other hand, processed, Western diets, which are associated with chronic diseases like cardiovascular disease and diabetes, are linked to decreased health-promoting bacteria in the gut.
An exciting area of future research is ‘psychobiotics’ – probiotics that positively affect mental health. Studies have linked various probiotics (and prebiotics) with maintaining the balance of key brain neurotransmitters to reduce anxiety and depression as well as reducing levels of the stress hormone cortisol.
The mechanisms linking the gut and brain are complex and include metabolite production, immune mechanisms and neuronal pathways (the vagus nerve). As scientists begin to understand more about how a healthy microbiome affects mood and psychology, the future may see therapeutic probiotics used to modulate mood. Given individual variation in microbiomes and diets, it may not come down to a single ‘pill’, but a combination of diet and psychobiotic therapy.
Dr Jocelyn Eason has a PhD in Plant Physiology from Otago University and an MBA from Massey University. In her current role, Dr Eason manages Plant and Food Research’s Food Innovation Portfolio, which includes teams that investigate human responses to food, the influence of food on human nutrition and wellness, and the production and supply of nutritionally rich foods.
The information and opinions within this column are not necessarily the views or opinions of Hot Source, NZ Food Technology or the parent company, Hayley Media.