Have you ever noticed how a warm bowl of soup can feel like a comforting embrace? Perhaps you’re familiar with the phrases ‘feel good food’ and ‘food for the soul’? Indeed, food is more than just sustenance; it has an incredible power to influence our mood and mental wellbeing, yet its impact often remains underestimated. With one in four individuals in the UK experiencing mental health challenges every year [1], understanding this profound connection has never been more critical.
Food and Mood: What’s the Connection?
There’s a growing body of evidence suggesting a deep connection between what we eat and how we feel. One of the most compelling studies in this area is the 2017 SMILES trial [2]. In this study, individuals with moderate-to-severe depression were randomly assigned to follow a Mediterranean diet (the intervention) or receive social support. The aim was to explore whether the Mediterranean diet, known for its emphasis on whole, unprocessed foods like fruits, vegetables, legumes, nuts, seeds, fish, and extra-virgin olive oil, could support a reduction in depression symptoms.
After just 12 weeks, the Mediterranean diet group achieved significantly greater improvements in depression symptoms compared to the social support group. Remarkably, one-third of these individuals achieved remission from depression, a rate four-times higher than that of the social support group.
Importantly, similar findings were observed in a 2019 study amongst adults with self-reported depression [3]. The Mediterranean diet not only significantly reduced depression symptoms but also improved the participants' mental health quality of life (QoL). What’s even more encouraging is that that these improvements were sustained even six months later, underscoring the long-term benefits of healthy eating.
More recently, a study focusing on young males with depression reaffirmed the positive impact of the Mediterranean diet on depression symptoms and QoL. Significant improvements in both depression symptoms and QoL were achieved through the diet, compared to befriending therapy, after 12 weeks [4]. Although it’s essential to consider these findings in the context of the specific population studied (males aged 18-25 years old), this study adds to an increasingly compelling picture around the benefits of a healthy diet for improved mental health.
But what if you’re not dealing with depression? The good news is that these benefits have extended beyond individuals with diagnosed conditions. A 2017 meta-analysis, which involved a comprehensive examination of several relevant studies, found that adhering to a healthy dietary pattern, such as the Mediterranean diet, was associated with a reduced risk of depression [5]. Conversely, a diet high in red and processed meats, refined grains, fat, sugar, and salt, coupled with low intake of fruits and vegetables (the typical 'Western diet' in the UK), was associated with an increased risk of depression. Moreover, high consumption of ultra-processed foods has also been linked to heightened anxiety symptoms [6].
So, we know that the food we eat influences how we feel. But what are the mechanisms driving this?
Inflammation
Inflammation is a natural and vital process in the body’s immune response. It occurs when the body detects an injury, infection, or damage of any kind. While acute inflammation is a necessary part of our defence system, chronic inflammation, which persists over an extended period, can be harmful; emerging research has highlighted an intricate relationship between inflammation and various mental health conditions including depression, anxiety and cognitive disorders. Examples of how chronic inflammation can negatively impact mental health include:
Altered neurotransmitter function: Inflammation can influence the production and regulation of neurotransmitters, which are chemicals that transmit signals in the brain. Chronic inflammation may reduce the availability of serotonin, a neurotransmitter associated with mood regulation and often referred to as the ‘happy hormone’. Lower serotonin levels are frequently observed in people with depression [7].
Neuroinflammation: Inflammation occurring in the brain can disrupt the normal functioning of neural pathways and neurotransmitter systems. This can lead to changes in mood, behaviour and cognitive function [8].
Hormone imbalance: Inflammation can affect our endocrine (hormonal) system, causing disruptions in hormonal balance. For instance, an increased release of cytokines (molecules involved in inflammation) can impact the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the body's stress response. Dysregulation of the HPA axis has been linked to mood disorders; for example, the production, release and regulation of serotonin and dopamine may be altered, which can negatively affect mood [9].
Reduced neuroplasticity: Chronic inflammation may impair neuroplasticity, which is the brain’s ability to adapt and reorganise itself. Reduced neuroplasticity can hinder the brain's capacity to recover from stress or trauma [10].
Impact on brain structure: Inflammation can even lead to physical changes in the brain. For example, it can reduce the volume of the hippocampus, a region of the brain crucial for memory, learning, emotions and stress response [11].
But how does the food we eat influence inflammation?
A diet that is nutrient poor and high in saturated fat, salt and refined sugar, like the typical Western diet, is known to increase inflammation by triggering the release of pro-inflammatory molecules [12]. This type of diet is often low in fibre too, which also contributes to inflammation; fibre not only possesses anti-inflammatory properties, but also helps regulate blood sugar levels, which can significantly impact mood, energy and concentration [13].
In addition to fibre, eating more foods rich in beneficial compounds called polyphenols can help to reduce inflammation and protect the brain [14]. Polyphenol-rich foods include blueberries, blackberries, spinach, olives, coffee and black tea and dark chocolate. Indulging in dark chocolate can have an added benefit – it triggers the release of endorphins, the ‘feel-good’ chemicals. It’s a win-win!
Healthy gut, healthy mind? The gut-brain connection
Have you ever noticed digestive issues when you’re feeling stressed? Or perhaps you’ve had a ‘gut feeling’ about something? These experiences are a testament to the existence of the gut-brain axis, a two-way communication system connecting the central nervous system (the brain and spinal cord) with the enteric nervous system, a network of nerves in the gastrointestinal tract. Through this intricate pathway, the brain and gut continually exchange information.
The gut-brain axis plays a pivotal role in regulating various bodily functions, including digestion, immune response and even our mood! At the core of this remarkable relationship lies the gut microbiota, the trillions of microorganisms inhabiting our intestines. Although we are still far from fully understanding the role of these gut microbes in mental health, we do know that they play a vital role in supporting our mental health in several ways:
Neurotransmitter production: The gut microbiota can influence the production and regulation of neurotransmitters including serotonin, dopamine and gamma-aminobutyric (GABA), all of which play key roles in mood regulation. In fact, did you know that around 95% of the body’s serotonin is produced in the gut? [15]
Metabolising mood-enhancing compounds: The gut microbiota can metabolise dietary components into substances that positively affect our mood. For example:
Short-chain fatty acids (SCFAs), which are produced by the gut microbiota as they ferment dietary fibre. SCFAs not only have anti-inflammatory properties, but also offer neuroprotective effects [16].
Amino acids such as tryptophan and tyrosine which serve as the precursors for serotonin and dopamine, respectively [17]. These amino acids cannot be produced by the body and so must be obtained through diet. (Poultry, salmon, beef, tofu, eggs, milk, yoghurt, beans, lentils, pumpkin seeds and oats are good sources of tryptophan and tyrosine).
Given this fundamental role in promoting good mental health, it is vital that we support and nurture a healthy and thriving gut microbiome. The key to achieving this is dietary diversity. Research has even suggested that individuals with depression tend to have lower diversity in their gut microbiota [18]. The good news is that we can influence this diversity through our diet, specifically by incorporating a wide range of plant-based foods, including fruits, vegetables, whole grains, pulses, nuts, and seeds. It’s also advisable to limit the consumption of ultra-processed foods, as evidence indicates that they can reduce microbiota diversity and promote inflammation [19].
Eating our way to better mental health
The relationship between diet and mental health is undeniably complex, and research continues to unveil its intricacies. Each person is unique and there’s no one-size-fits-all solution when it comes to diet and mental wellbeing. However, certain key nutrients have shown significant promise in positively influencing mental health. These nutrients can serve as a solid foundation when considering what to include in our diets:
Food for Thought
Our diet and mental health share an intricate connection and nourishing our minds is just as essential as nourishing our bodies. By focusing on nutrient-dense foods, we can positively influence our mood, cognitive function and overall mental wellbeing.
It’s vital to remember that while diet plays a pivotal role in preventing, treating and recovering from mental health conditions, it’s not a silver bullet. Each of us is unique, with differing lifestyles and preferences, so it’s important to find what works best for you!
For individuals with diagnosed mental health conditions, especially those taking medications, seeking guidance from a healthcare professional is paramount. This will ensure that dietary changes align with your comprehensive treatment plan, thereby enhancing overall wellbeing.
Lastly, diet is an incredibly powerful tool, but it’s one piece of the puzzle. A holistic approach to mental wellbeing is essential; this may encompass various lifestyle adjustments such as maintaining regular exercise, increasing mobility, fostering social connections, reducing alcohol and tobacco consumption and practicing good sleep hygiene [20]. This approach, alongside therapy and medication where necessary, offers the most comprehensive path to mental wellness.
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This article was written by Sophie Strongman, MSc ANutr.
Hello, my name is Clem.
I’m an evidence-based, award-winning nutritionist (MSc, RNutr) and workplace wellbeing specialist.
I help organisations and individuals make sense of nutrition to nurture their health and wellbeing.
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References
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