✍️ Isabel Baxter | Neuroscience Graduate from the University of Leeds
Food and Mood: Are They Connected? 🔗
We know that a poor diet damages our physical health, but how does it affect our mental health?
Unhealthy diets increase our risk of cardiovascular, metabolic, and gastrointestinal disorders. Whilst the impact of what we eat on our physical health is well acknowledged , the impact of our diets on our mental health is less recognised. However, there is increasing evidence that poor dietary choices also increase our risk of developing a mental illness, namely, depression. Indeed, in 2010, Jacka and colleagues reported that depressive symptoms were more severe in individuals following a 'western diet', high in sugary foods, refined grains, and alcohol, relative to those who followed a dietary pattern high in fruit, vegetables, fish, and wholegrains. Similarly, in 2023, Contreras-Rodriguez and team observed that an increase in the consumption of ultra-processed foods and drinks was associated with increased depressive symptoms.
Salads and Serotonin: How Does Your Diet Affect Your Brain Chemistry? 🧠
Neurotransmitters are chemical messengers within the brain which underpin the functions of the nervous system. For instance, serotonin is involved in pain perception, wound healing, and the regulation of sleep. Notably, serotonin is also implicated in the aetiology of depression.
Plant foods, including nuts, seeds, and wholegrains, are rich sources of the amino acid tryptophan - the precursor of neurotransmitter serotonin. As depression is commonly attributable to a depletion of serotonin, it is likely that a tryptophan-rich diet is protective against the development of depression. Indeed, a study in 2016 observed that individuals who transitioned to a low tryptophan diet for 2 weeks had an increase in depressive symptoms. Similar results were replicated by Reuter and colleagues in 2021, who reported that a lower tryptophan intake is associated with more depressive symptoms.
Mood-Modulating Microbes: What is the Role of the Gut in Depression? 🦠
As well as increasing our tryptophan intake, we can also manipulate our gut microbiome to promote serotonin production, and thus, reduce our risk of developing depression. Certain species of gut bacteria increase serotonin release, namely, Bifidobacterium dentium. Fermented foods, including natto, sauerkraut and sourdough bread, promote the growth of Bifidobacterium, and therefore, may support the production of serotonin. This may explain why traditional Japanese diets, which are high in fermented soya products, are associated with a lower prevalence of depression. Changes to our diets may also promote an increase in the gut bacteria Firmicutes, which may, in turn, protect against the development of depression. Indeed, supplementation with whole grain cereals increases the levels of Firmicutes. Given that individuals with depression have a lower abundance of Firmicutes. a diet high in whole grain cereals may be protective against depression.
Preventing Depression: What is the Dream Diet? 🥗
The Mediterranean Diet emphasises the consumption of minimally processed plant foods, including fruits, vegetables, wholegrains, nuts, seeds, and olive oil, as well as a moderate intake of fish and eggs.
The Mediterranean diet is well recognised for its cardiovascular benefits, however, its benefits likely also extend to one's mental health. Indeed, several investigations hail the Mediterranean diet for its antidepressant capacity. Notably, in a randomised-controlled trial in 2017, Jacka and colleagues observed that after following the Mediterranean diet for 12 weeks, participants exhibited less depressive symptoms.
In part, the high omega-3 fatty acid content of the Mediterranean diet likely underpins its anti-depressant capacity. The Mediterranean diet emphasises the consumption of fish, which is rich source of omega-3. Indeed, salmon has an EPA and DHA (two types of omega-3 fatty acids) content of approximately 0.59 and 1.24 grams per serving, respectively. With fish or omega-3 intake being associated with a reduced risk of depression, this may partly account for the antidepressant capacity of the Mediterranean diet.
Similarly, a higher intake of vitamins B6, B2, and B1, which are high in fish, eggs, and wholegrains, respectively, have also been linked to a reduced depression risk. As well as B vitamins, a greater intake of vitamin C - which is found in several types of fruits and vegetables, including peppers, strawberries, and green leafy vegetables, is also associated with a lower likelihood of depression. Importantly, olive oil intake is also inversely associated with a lower risk of depression.

Edited by: Grace Pountney (Founder and Copywriter)
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