Food & Mood Masterclass 2026 Pre-reading

There is substantial evidence available that supports the importance of health-related actions, such as dietary choices, in preventing and addressing mental illness as well as the physical health issues commonly experienced by individuals with mental illness. It is widely recognized that individuals with severe mental illness have a significantly shorter lifespan of 10 to 20 years compared to the general population, primarily due to the presence of chronic physical ailments.

A growing body of evidence from epidemiological, pre-clinical, and clinical research, points to the significant role of diet in promoting mental and brain health. Integrating dietary interventions alongside conventional treatments shown to be highly effective and cost-efficient in addressing mental health symptoms and enhancing the overall physical health and well-being of individuals with mental health conditions.

Prior to exploring the core principles of Nutritional Psychiatry during our  Masterclass, it is important to review fundamental information on nutrition and diet. Although this section may appear rudimentary to some, it is advised to spend a brief amount of time reviewing it as it will assist in understanding the key concepts presented during the Masterclass. While we will not extensively explore the topic, we will cover enough to gain a basic understanding of the principles that form the foundation of the connection between nutrition, diet, and mental health.

Energy and macronutrients

The energy needed for sustenance is acquired from macronutrients found in food, namely carbohydrates, proteins, and fats. Although fibre and water are not traditionally regarded as energy sources, they can also be classified as macronutrients. Each of these macronutrients serves a distinct purpose in metabolic functions.

Carbohydrates

Carbohydrates are crucial macronutrients as they serve as the primary source of energy production. In recent years, there has been considerable debate regarding the recommended carbohydrate intake for a healthy diet. However, when it comes to managing physical health aspects such as body weight or the risk of heart disease, there is little to no significant difference observed between low-carbohydrate diets and balanced-carbohydrate diets.

Moreover, prospective studies and meta-analytical data indicate a U-shaped relationship between carbohydrate consumption and mortality. This means that both high intake (exceeding 70% of daily energy intake) and low intake (less than 40% of daily energy intake) pose higher risks.

The type and quality of carbohydrates play a critical role. For instance, ultra-processed cakes and biscuits often contain a significant amount of sugar, which is classified as carbohydrates. However, whole grains and root vegetables are typically rich in important fibrous and starchy carbohydrates.

Fats

Dietary fats, or fatty acids, are a valuable source of energy. They encompass saturated, monounsaturated, and polyunsaturated fats, which can be found naturally in animal-based foods (predominantly saturated fats) and plant-based foods (mostly monounsaturated and polyunsaturated fats). Trans fats, on the other hand, although can be found in animal-based foods, are usually formed through the hydrogenation process of vegetable oils.

Proteins

Dietary proteins are broken down into amino acids. These play a vital role in cellular structure and function. While the body can synthesize certain amino acids, there are essential amino acids like leucine and tryptophan that must be obtained through dietary sources. Both animal and plant-based protein sources contain the necessary amino acids for maintaining good health.

Evidence suggests that the source of dietary fat and protein is important, as plant-based fats and proteins may offer more favourable health outcomes compared to those derived from animals.

Fibre

Dietary fibre is essential for optimal health, and usually is consumed with plant-based foods. In general, dietary fibre refers to the components of plants that are either poorly digested or not digested at all in the human gastrointestinal tract. Adequate consumption of dietary fibre is linked to numerous health benefits. Fibre also play a crucial role in promoting optimal functioning of the gut microbiota.

Micronutrient: vitamins and minerals

Micronutrients, which include vitamins and minerals, play a crucial role in various chemical processes, including those related to metabolism. While these micronutrients are necessary in small quantities, they do not contribute to the body’s energy supply.

Fat-soluble vitamins (A, D, E, and K) are found in dairy products and plant oils, while water-soluble vitamins (B and C) are primarily sourced from plant foods like fruits and vegetables. In a well-balanced diet, most individuals do not require vitamin supplements.

Dietary minerals, such as calcium, potassium, and magnesium, as well as trace elements like zinc, selenium, and iron, are generally abundant in balanced diets.

However, some vitamin, mineral and trace element supplementation may be necessary for older adults, women of reproductive age or individuals with special needs.

Polyphenols

Polyphenols are bioactive compounds that occur naturally in various plant-based foods such as fruits, vegetables, grains, legumes, nuts, seeds, and other plant sources. Polyphenols exhibit antioxidant and anti-inflammatory properties, which have the potential to provide protection against non-communicable diseases like cancer, metabolic disorders, and degenerative conditions. Consumption of polyphenols has been also implicated in the gut microbiota composition and function. Additionally, polyphenols have been considered as an adjunctive treatment in psychiatric and neurodegenerative disorders.

Extent of food processing

Most food we consume undergoes some degree of processing. Historically, food processing has been employed to prepare and preserve food, improve its taste and sensory attributes, and offer a wider range of food choices. However, in today’s food system, the extent of processing and its impact on our health is a crucial concept. It is important to consider the number of steps or transformations involved in the production of a specific food product, as well as the type and quantity of ingredients added during processing.

Briefly, unprocessed or minimally processed foods mainly consist of edible plants and animals. Examples include fruits, vegetables, whole grains, legumes, nuts, seeds, and proteins like meat, poultry, fish, and milk. Even if these foods have undergone basic processes such as cutting, cleaning, freezing, or packaging, they can still be considered minimally processed.

Processed foods, on the other hand, refer to foods that have been cooked, baked, smoked, or canned, often with the addition of processed culinary ingredients like oils, butters, flours, starches, sugar, and salt. Examples include canned vegetables (including packaged kimchi), smoked meats, and fruit juices. Although the palatability and shelf life of these foods are enhanced, their level of processing and ingredient list is usually not extensive.

Ultra-processed foods and beverages are food products that have undergone multiple commercial processing methods, such as extrusion or hydrogenation. These foods typically contain a wide range of added ingredients, including those that enhance flavour and taste, while being low in whole foods. Ultra-processed foods are designed to be highly palatable, convenient, appealing, and heavily marketed. However, they tend to have a poor nutritional profile, and their consumption is associated with negative impacts on human health and the environment.

Diet quality and dietary styles

The food we eat is complex (and tasty!) combination of macro- and micronutrients and compounds. It is important to appreciate the quality of our diet, which can be categorized as either high-quality or low-quality:

• High-quality diets are primarily based on minimally processed vegetables, legumes, fruits, and grains, with the inclusion of oils, plant proteins, and animal proteins.
• Low-quality diets, on the other hand, consist mainly of highly processed and refined foods that contain high amounts of added sugar, salt, animal fats, and food additives.

Another way to view dietary intake is through the lens of tradition and culinary history. Traditional-style diets are based on the habitual dietary intake and traditional cuisines of various cultures worldwide. The Mediterranean diet, African Heritage diet, and Traditional Nordic, Scandinavian, and Japanese diets are examples of traditional diets.

The defining characteristic of traditional diets is the high consumption of unrefined plant foods. These diets typically involve minimal processing, with a significant proportion of foods consumed raw or cooked at low temperatures. If preservation methods are used, they are typically natural methods such as fermentation or drying. While traditional diets often include the consumption of animal products, they are usually consumed in smaller portions, and sweet or highly refined foods are consumed infrequently.

In contrast, the Western-style diet is a relatively new concept characterized by modern approaches to food production, processing, and distribution. This style of eating is associated with excessive consumption of energy-dense, nutritionally poor foods. Western diets often involve a high consumption of animal products, foods high in added sugar, salt, and highly processed grains. These foods are typically low in fiber, vitamins, and minerals. The Western-style diet is also characterized by high levels of food processing, including deep frying, refining, and the use of various food additives.

In addition to the division between traditional and Western-style diets, dietary styles can be further described as:

• Plant-based: where most consumed foods are of plant origin.
• Vegetarian: where animal meats and seafood are excluded, but eggs and dairy may be included.
• Pescatarian: similar to vegetarian, but with the inclusion of seafood.
• Vegan: where no animal products are consumed.
• Flexitarian: a mostly vegetarian or vegan dietary style with occasional consumption of animal-based products.

A person’s dietary style is influenced by various factors, including biological factors such as hunger and taste preferences, personal factors such as knowledge and beliefs, environmental factors such as access to certain foods, economic factors such as cost and availability, and social factors such as culture and the social environment. All these factors can serve as barriers or motivators and should be considered in the context of dietary behaviour.

The potential connection between diet and mental health disorders may be clarified by considering the influence of diet on various physiological pathways related to the development of these disorders.

Numerous interconnected physiological pathways provide a possible explanation for the impact of diet on mental and cognitive well-being.

While the existing clinical studies primarily concentrate on investigating the biological dysregulations associated with depression, it is important to note that other mental health conditions, including anxiety, bipolar disorder, and schizophrenia, exhibit similar pathophysiological characteristics and regulatory mechanisms.

The diagram presented below demonstrates the involvement of diet in various mechanisms. The green arrows indicate the potential positive modifications that can result from a healthier diet. Conversely, the red arrows represent the possible adverse effects of the Western diet. This diet can have detrimental consequences on both mental disorder symptomatology and metabolic outcomes. We review some of these mechanisms in the sections below.

Inflammation

In recent decades, there has been substantial evidence establishing a strong connection between inflammation and numerous psychiatric disorders. For example, inflammation worsens the symptoms of depression, and elevated levels of inflammatory markers are commonly observed in depression and other neuropsychiatric conditions.

Gut microbiota

The human gut microbiome is essential in maintaining homeostasis of its host. The Microbiota-Gut-Brain axis is implicated in psychiatric, neurodevelopmental, and neurodegenerative disorders. People affected by psychiatric disorders have consistent differences in their gut microbiota profiles compared to those without.

The interaction between the gut microbiota, the brain, and the immune system is a crucial factor in psycho-neuro-immunological processes. The gut microbiota influences neurogenesis, the functioning of the hypothalamic-pituitary-adrenal (HPA) axis, and the metabolism of tryptophan-kynurenine. Moreover, the microbiota plays a role in the production and breakdown of several neuroactive substances, including short-chain fatty acids (SCFAs), neurotransmitters, gut hormones, and neuroprotective antioxidants.

Neurogenesis

Cognitive processes and mood regulation are influenced by hippocampal neurogenesis. Disruptions in adult hippocampal neurogenesis can affect the stress response, emotions, information processing, and social interactions. Studies on animal models of depression have demonstrated associations between reduced neurogenesis and depressive behaviour.

Brain-derived neurotrophic factor (BDNF), a neurotrophic molecule highly expressed in hippocampal neurons, plays various roles in neuroplasticity, synaptic strength, and neurogenesis. Both experimental and observational studies have shown decreased levels of BDNF in conditions such as stress, severe mental illness, and neurodegenerative disorders. On the other hand, a healthier dietary pattern, has been associated with higher plasma BDNF levels. However, although preclinical research has indicated a correlation between blood and cortical levels of BDNF, this relationship is not yet fully understood in humans.

Findings from two long-term human studies, have indicated that diet quality over time can have an impact on human hippocampal volume. The results of the first study showed an independent association between a lower intake of nutrient-dense foods and a higher intake of unhealthy foods with a smaller left hippocampal volume. The second study reported a correlation between a larger hippocampal volume and adherence to a diet characterized by a higher consumption of foods like fresh vegetables, whole grains, and those containing omega-3 fats, while also having a lower consumption of sugar-sweetened drinks, red and processed meat, and foods rich in trans-fat and sodium.

Oxidative stress and mitochondrial disfunction

Evidence shows a relationship between the markers of oxidative stress and depression, with individuals with depressive symptoms presenting with a lower antioxidant capacity and greater levels of oxidative stress markers than those without depressive symptoms. Additionally, accelerated oxidative stress may play a key role in declining states and neuroprogression of psychiatric disorders.

Mitochondrial dysfunction has been linked to various primary psychiatric disorders, including depression, bipolar disorder, and schizophrenia. One crucial factor that contributes to key characteristics of psychiatric pathology, such as physical and mental fatigue, could be the impaired production of adenosine triphosphate (ATP) by mitochondria, which is essential for supplying energy to most cellular processes.

The function of mitochondria can be influenced, at least in part, by diet. For instance, diets high in saturated fats that promote inflammation have been associated with increased production of free radicals and mitochondrial dysfunction. On the other hand, adopting healthy diets and certain nutrient supplements may help reduce oxidative damage to mitochondrial DNA and restore its normal function.

Tryptophan-kynurenine metabolism

Tryptophan, an essential amino acid that the body cannot produce on its own and must be obtained through the diet, serves as a precursor for neuroactive compounds, particularly serotonin. The tryptophan-kynurenine pathway is responsible for the breakdown of approximately 90% of dietary tryptophan. During this process, various bioactive metabolites, such as kynurenines, neuroprotective acids (like kynurenic acid), neurotoxic acids (such as quinolinic acid), nicotinamide adenine dinucleotide (NAD), and others, are produced. The role of these metabolites is increasingly recognized in neuropsychiatric disorders. Severe psychiatric disorders are characterized by disturbances in the tryptophan-kynurenine pathway, leading to a shift away from serotonin production and an increased emphasis on the kynurenine pathway. This shift highlights the potential significance of this pathway in the pathology of neuropsychiatric disorders.

Epigenetics

Environmental factors can cause epigenetic changes, which impact the regulation of gene expression without altering the DNA sequence itself. Among these environmental factors, diet and nutrition play a crucial role. Epigenetic modifications of genes within the central nervous system are particularly notable during prenatal development, but they may also occur in the adult brain as a response to environmental stressors.

Motivational interviewing  

Motivational interviewing is an approach that aims to support individuals to find the motivation to make positive changes to behaviours. This approach is particularly effective for people who have mixed feelings about changing their behaviour. The core elements of motivational interviewing include:

• Empathic presence and skilful listening;
• Communicating empathy and non-judgment;
• Honouring autonomy; and
• Evoking another’s thoughts, feelings, goals, and solutions around behaviours causing difficulties.

The principles of motivational interviewing (MI) were developed in part by clinical psychologists William R. Miller and Stephen Rollnick, through the integration of several psychological theories described below.

Client Centred Therapy was developed by the humanistic psychologist Carl Rogers. This approach to therapeutic relationships emphasizes holding and maintaining unconditional positive regard with our clients. This concept is highlighted as absolute worth in Motivational Interviewing.

Unconditional positive regard describes an essential recognition of our client’s humanity, and an attitude that remains undeterred by any problematic client behaviours for a successful outcome. Typically, the client experiences this as ongoing acceptance, understanding, and warmth.

An acceptance of this other individual as a separate person, a respect for the other as having worth in his or her own right. It is a basic trust – a belief that this other person is somehow fundamentally trustworthy.” (Rogers, 1980)

Self-Determination Theory (SDT) was developed by Edward Deci and Richard Ryan and emphasizes the distinction between types of motivation and how these types of motivation influences behaviour:

• Extrinsic motivation – when we are motivated by external factors such as reward systems, grades, evaluations, financial success, or the opinions of others.
• Intrinsic motivation – when we are motivated from within, by interests, curiosity, care or abiding values. Intrinsic motivations are not necessarily externally rewarded or supported, but nonetheless they can sustain passions, creativity, and efforts.

It is useful to think of motivation on a continuum ranging from “non-self-determined to self-determined.”

• At one end of the spectrum, we have amotivation, in which an individual is completely non-autonomous, has no drive to speak of, and is struggling to have any of their needs met.
• In the middle, we have several levels of extrinsic motivation.
• At the other end of the continuum, intrinsic regulation, an individual is entirely motivated by intrinsic sources. The individual is self-motivated and self-determined, and driven by interest, enjoyment, and the satisfaction inherent in the behaviour or activity they are engaging in.

Research suggests that intrinsic motivation generally leads to the most positive outcomes for individuals.

Additionally, SDT considers the basic human needs of autonomy, competence, and relatedness. According to SDT, when someone feels autonomous to control their own behaviour, has the knowledge and skills to achieve the desired outcome, and perceives genuine support from others, then they are more likely to put in the effort and persist in changing that behaviour.

The Transtheoretical Model (TTM) of change in health psychology explains or predicts a person’s success or failure in achieving a proposed behaviour change. It attempts to answer why a change was successfully implemented and maintained, or alternatively why the change was not made. The transtheoretical model (TTM) has proven successful with a wide variety of simple and complex health behaviours, including dietary change, exercise acquisition, and substance use behaviours.

The TTM is based on more than two decades of research led largely by Prochaska and colleagues. This research has found that individuals move through a series of five stages (precontemplation, contemplation, preparation, action, maintenance) in the adoption of healthy behaviours or cessation of unhealthy ones.7 The five stages of change are precontemplation, contemplation, preparation, action, and maintenance.

1. The pre-contemplative stage. There is no intention to change a behaviour in the foreseeable future. Your client might not be aware that a change needs to happen.
2. The contemplative stage. There is an awareness that a problem exists. Your client might be seriously thinking about overcoming the problem but has not yet made a commitment to take action.
3. The preparation stage. There is both intention and some preparation to take action, such as gathering information, setting goals or thinking about how to create change. Your client might have attempted to take action but had little or no success.
4. The action stage. Action is taken to modify behaviour, experiences, or environment in order to overcome a problem. Your client might be using considerable effort, time and energy to apply new behaviours and learn from mistakes or lapses.
5. The maintenance stage. There is intention and effort to prevent relapse and consolidate the gains attained during the action stage. Your client might be reviewing and monitoring their progress, and trying to sustain the change.

Understanding where your client is in these stages can help you to identify where you need to start, and where you might progress, in supporting them to create change.

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