What role can diet play in supporting mental health?
Food and mood rhyme for a reason as the two are intrinsically linked. What we eat directly correlates to how we feel. Ever felt wired after too much caffeine? Or jittery after too much sugary food? The intricate relationship between the human gut microbiome and the brain is now shedding light on just how much our diets impact our mental wellbeing.
The word ‘diet’ has mistakenly become synonymous with weight loss and physical wellness but refer to its actual meaning and it simply indicates “the kinds of food that a person, animal, or community habitually eats”. These foods, as we now know, can influence both physical and mental health for better or for worse. Connecting the dots between food and mood has undoubtedly been one of the nutritional break-throughs of the last few decades, with more and more focus now being given to the importance of ‘diet’ in prevention and support of mental health disorders such as acute stress, depression, anxiety, post-natal depression (PND), Attention Deficit/Hyperactivity Disorder (ADHD), autism spectrum disorder (ASD) and many others. Unravelling the complex communication system between our gut microbiome and the brain has allowed nutritional scientists to explore the beneficial effects of nutrients from foods on our mood. As we have discovered more about the benefits of whole foods and their nutrients we have simultaneously learnt about the accumulative risks of over-consuming high sugar, salt and fats in ultra-processed foods and drinks (UPFDs). Connecting these dots can help transform your diet – the kinds of foods you habitually eat – to better support your psychological (and physical) wellbeing.
It all begins in the gut.
Whilst the brain may be our body’s control centre, the gut is the power station processing and distributing the fuel, without which nothing functions. Here the story gets interesting as we need to consider both the ‘type of fuel’ e.g. the foods we consume, and also enter into the world of the gut microbiome – a thriving microbial community bursting with trillions of helpful commensal bacteria, fungi and other microbes. The gut microbiome plays an important role in your health by helping control digestion of foods plus the absorption of nutrients found in those foods to supply the body with energy. The gut is also home to 70% of your immune system where the diversity of bacteria helps the body identify and eliminate pathogens (1). Lastly, the gut cross-talks with the brain to create the ‘gut-brain axis’ relevant to our mental health status.
The Gut Brain Connection
The gut and the brain communicate bi-directionally linking emotional and cognitive centres of the brain with peripheral intestinal functions which influence mood, cognition, and mental health. Interestingly, your gut contains 500 million neurons, which are connected to your brain through nerves in your nervous system, the vagus nerve being the largest (2). Our gut and brain are also connected through chemicals called neurotransmitters. Neurotransmitters produced in the brain control feelings and emotions. For example, the neurotransmitter serotonin contributes to feelings of happiness and also helps control your body’s natural body clock known as circadian rhythm. Many of these neurotransmitters are also produced by your gut and the trillions of microbes living there. Research shows that the gut microbiota profoundly influences the gut-brain relationship (i.e., mental state, emotional regulation, neuromuscular function, and regulation of the hypothalamic-pituitary-adrenal (HPA) axis) (3). The last of these, the HPA axis, is involved with the body’s reaction to stress and is activated when something stressful happens to us. Once activated the brain releases the hormones adrenalin and cortisol in response to the stressor to increase heart rate and glucose circulation and provide the body with the tools to cope (4). That the gut microbiome can influence processes such as these is perhaps the first clear indication of where food creeps into the story. The foods we eat are key to maintaining a healthy and functional gut, as well as providing nutrients to the microbes that populate it. In return, these microbes help guide the emotional and cognitive centres of the brain.
What can go wrong?
Where does this gut-brain relationship breakdown in relation to mental health?
To explain this, we must first take a step back and explore optimal gut function. Food consumed passes through the gastro-intestinal tract and is duly processed at each stage of digestion. Nutrients are broken down and transported around the body, including to the brain where they must cross the blood brain barrier (BBB) to enter and be absorbed. If these digestive processes become dysregulated or nutrient status disrupts the balance of microbes in the gut – known as bacterial dysbiosis – this directly affects the delivery of nutrients to the brain. One way this can happen is through over consumption of ultra-processed foods and drinks, which can alter the gut microbial composition. A recent study showed that the prevalence of anxiety and depression were significantly higher in participants who consumed more than 5 servings/day of UPFDs compared with those who consumed less than 3 servings/day (5). Several things start to happen to explain the link to mental health symptoms. Firstly, these UPFDs lack sufficient nutrients to nourish the gut microbes leaving them unable to perform their digestive duties as optimally as before. Secondly, the internal integrity of the gut and its lining can deteriorate giving rise to leakage (often referred to as leaky gut). Leaked nutrients are free to travel around the body causing havoc, having not been fully digested and distributed as normal. If these rogue nutrients make it across the blood brain barrier they can influence the brain’s normal activities, giving rise to mental health symptoms and/or exacerbating existing symptoms.
Which Foods support Mood?
Nutrition is a key modulator of our gut microbiome, which is a key modulator of our mind and our mood. What does that really mean? It means we need to consume more of the foods with beneficial nutrients such as a protein, healthy fats, fibre, vitamins, and minerals to keep our body energised and our microbes well-fed. We not only feed ourselves but with every mouthful are also feeding the trillions of microbes within. And they like to be fed a certain way. The typical “Western” dietary pattern, consisting of sweet and fatty foods, refined grains, fried and processed foods, red meat, high-fat dairy products, and low fruit and vegetable intake, is associated with a higher incidence of depression (6).
Correlative studies in healthy adults show that a lower incidence of depression occurs in those who eat according to “healthy” dietary patterns, characterised by an abundance of vegetables, fruits, cereals, nuts, seeds, and pulses, as well as moderate amounts of dairy, eggs, and fish and unsaturated fats (7).
Increased consumption of a diet rich in fresh fruits and vegetables has been associated with increased reported happiness and higher levels of mental health and wellbeing (8,9,10).
Higher Omega-3 levels, the essential fatty acids found in oily fish, nuts, seeds and algae, have been suggested to reduce the occurrence of depression (11).
These scientific findings demonstrate the unequivocal link between nutrition and mental health and pave the way for integrated personalised nutrition and lifestyle medicine approaches.
Figure 1: Diet has been linked with the risk of developing depression and anxiety; there are direct effects from …
Adv Nutr, Volume 11, Issue 4, July 2020, Pages 890–907, https://doi.org/10.1093/advances/nmaa016
So where do you go from here?
A natural first step to optimising your gut-brain cross-talk is to cut down on the ultra-processed foods and drinks. Imagine a conversation that was continually interrupted by people interjecting with unwanted comments? This is essentially what high sugar foods do. They spike blood-glucose levels and draw the body’s attention to dealing with this, thus interrupting the usual flow of conversation between the gut and the brain. Instead, opt for more of the whole food ingredients and work towards adding in more fruits and vegetables, nuts, seeds, pulses, wholegrains, lean proteins and healthy fats.
To take this a step further, working with a Registered Nutritional Therapy Practitioner can help you fully evaluate your diet and optimise your nutrient intake as part of a wider dietary protocol to support your mental health and wellbeing. Practitioners are qualified in personalised nutrition and work on a one-to-one basis to help individuals implement a food-first approach in the promotion of health, peak performance, and individual care.
Author BANT Registered Nutritionist ® Claire Sambolino MSc, NTPD, mBANT, rCNHC
Tags: anxiety, blood brain barrier, claire sambolino, cognition, depression, diet, food, food and mood, gut microbiome, gut-brain axis, lifestyle medicine, mental health, mood disorders, nutrition, nutritional therapy, personalised nutrition, Registered Nutritional therapy practitioner