Nourishing Your Mind: The Impact of Diet on Mental Health

Feeding Happiness

Ever wondered how the food on your plate might be affecting your mood and mental clarity? Nourishing your body can also nourish your mind. Recent studies have identified the significant role of specific nutrients in promoting emotional well-being and improving some symptoms of anxiety and depression. These include omega-3, vitamins, antioxidants, probiotics etc. The majority of these have been identified to decrease chronic inflammation in the brain which has been linked to psychiatric disorders.

Antioxidants

Antioxidants are molecules that help protect the body from damage caused by harmful molecules that can damage cells and contribute to aging and diseases like cancer and heart disease. They are mainly found in fruits, vegetables and nuts. Antioxidants include vitamins C and E, flavonoids, and polyphenols.

Lopresti et al., (2013) found a strong link between increased antioxidant intake and mental health outcomes. Antioxidants play a crucial role in maintaining mental health by combating oxidative stress. Oxidative stress is associated with the development and progression of various mental health disorders, including depression, anxiety, and cognitive decline. Oxidative stress can lead to cellular damage, inflammation, and neurodegeneration, all of which are linked to mental health disorders (Halliwell, 2006). The body’s antioxidant defence system includes enzymatic antioxidants like superoxide dismutase (SOD) and glutathione peroxidase (GPx), and non-enzymatic antioxidants such as vitamins E and C, carotenoids, and polyphenols (Bouayed & Bohn, 2010).

Depression is often accompanied by increased oxidative stress and decreased antioxidant defences. Studies have shown that antioxidant supplementation can reduce depressive symptoms by mitigating oxidative damage and inflammation (Ng et al., 2008). Furthermore, antioxidants protect the brain by preserving neuronal integrity and function, reducing inflammation, and promoting neurogenesis (Berk et al., 2013). Neurogenesis is the process by which new neurons are formed in the brain, particularly in the hippocampus (brain region associated with learning, memory, and emotional regulation).

Omega-3

Omega-3 PUFAs, which include eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential nutrients found in fatty fish-like salmon and in fish-oil supplements. These fatty acids are crucial for brain health due to their roles in modulating neurotransmitters, reducing inflammation, antioxidation, and promoting neuroplasticity (Su et al., 2015; Young, 2007; Dinan et al., 2013). Recent research has shown that omega-3 PUFA supplements can have positive influences on the treatment of major depression disorders, bipolar disorders, interferon-α-induced depression in chronic hepatitis C patients, and posttraumatic stress disorders (PTSD) (Su et al., 2015).

Omega-3 PUFA levels are often lower in patients with mood disorders, further supporting their role in mental health (Su et al., 2015). Patients with major depressive disorder have been found to often have decreased levels of EPA and DHA in their blood and brain tissues. Omega-3 PUFAs have anti-inflammatory properties that help reduce inflammation in the brain, which can alleviate symptoms of depression and anxiety (Dinan et al., 2013; Sánchez-Villegas et al., 2009). They reduce oxidative stress, which is implicated in the pathophysiology of mood disorders. By combating oxidative damage, these fatty acids support overall brain health (Su et al., 2015). Oxidative stress happens when the body produces more harmful molecules than it can neutralise with antioxidants, leading to potential damage to cells. Additionally, fatty acids promote neuroplasticity, the brain’s ability to reorganise itself by forming new neural connections. This is essential for recovery from depression and anxiety, as it enhances the brain’s capacity to adapt and function optimally (Su et al., 2015).

Vitamin B12 & Folate (Vitamin B-9)

Folate (vitamin B-9) is essential for red blood cell formation and healthy cell growth and function. This nutrient is especially crucial during early pregnancy to reduce the risk of birth defects in the brain and spine. Folate is predominantly found in dark green leafy vegetables, beans, peas, and nuts. Folate deficiency is often found in patients with depression, which may be due to reduced appetite associated with depression. Meanwhile, vitamin B-12 is crucial for red blood cell formation, cell metabolism, nerve function, and DNA production. It is found in animal products like poultry, meat, fish, dairy, fortified cereals, and available as supplements or prescribed injections.

Folate plays a role in the production of serotonin and other neurotransmitters. Deficiency in folate can lead to low levels of serotonin metabolite 5-HIAA in the cerebrospinal fluid, potentially linking folate levels to mood regulation. Some studies suggest folate deficiency might contribute to the onset of depression, while others indicate that it may prevent recovery. Supplementing antidepressant treatment with folate has shown some evidence of improving patient outcomes, although it is unclear if this benefit is limited to those with a folate deficiency (Young, 2007). S-adenosylmethionine (SAMe), which is involved in neurotransmitter synthesis, is affected by folate levels. Folate deficiency reduces SAMe, which is an established antidepressant and increases CSF 5-HIAA levels (Bottiglieri, 2009).

Furthermore, folate and vitamin B12 are crucial for the synthesis of neurotransmitters and the metabolism of homocysteine – an amino acid linked to neurotoxicity and vascular damage. Low levels of these vitamins can lead to elevated homocysteine, which has been implicated in depression and cognitive dysfunction (Wu et al., 2020; Zhang et al., 2022).

Randomised controlled trials have shown that supplementation with folate and vitamin B12 can help reduce depressive symptoms, particularly in older adults. Walker et al. (2010), demonstrated that combined supplementation of folic acid and vitamin B12, along with psychoeducation and physical activity promotion, significantly reduced depressive symptoms in older adults with elevated psychological distress. Systematic reviews and meta-analyses found that higher dietary intakes of these vitamins were linked to a lower risk of depression and cognitive decline (Holmes et al., 2011).

Probiotics and Gut-Brain Axis

Probiotics are live microorganisms that, when consumed in adequate amounts, confer health benefits on the host, particularly in terms of gut health. They are often referred to as “good” or “beneficial” bacteria because they help maintain a healthy balance of gut microbiota, which is crucial for overall health, including mental well-being. Probiotic foods, such as yogurt, kefir, and fermented vegetables, can improve gut health and have been linked to reduced anxiety and depression symptoms. A randomised controlled trial found that probiotic supplementation improved mood and reduced stress in healthy volunteers (Messaoudi et al., 2011).

The gut-brain axis is a bidirectional communication network that links the central nervous system with the enteric nervous system, facilitating interaction between the gut and brain. Probiotics play a significant role in this communication, influencing brain function and behaviour. Gut microbiota extensively influence mood, cognition, and mental health, with disruptions linked to mood disorders and gastrointestinal diseases (Sudo et al., 2004). It can impact brain chemistry and is involved in the production of neurotransmitters like serotonin, which regulate mood (Cryan & Dinan, 2012).

Initial studies showed that gut bacteria like Campylobacter jejuni could induce anxiety-like behavior in animals without an immune response, highlighting the gut’s role in brain function (Goehler et al., 2005). Gut microbiota extensively influence mood, cognition, and mental health (Sudo et al., 2004). The vagus nerve, enteric nervous system, and neurotransmitters like GABA and serotonin within the gut influence brain function (Bercik et al., 2011). Gut microbiota alter nutrient availability and release peptides affecting the HPA axis and stress responses, like galanin (Söderholm & Perdue, 2001). Short-chain fatty acids (SCFAs) produced by gut bacteria have hormone-like activity and can cross the blood-brain barrier, influencing brain development and behavior (Frost et al., 2014). Gut microbiota influence inflammation and immune responses, which are implicated in psychiatric disorders like depression (Mayer et al., 2014). Stress and gut dysbiosis can increase intestinal permeability (“leaky gut”), leading to inflammation and mental health issues (Zhang et al., 2016).

Several studies have shown that probiotics can reduce symptoms of depression and anxiety; Messaudi et al. (2011), found that participants who consumed a probiotic supplement containing Lactobacillus and Bifidobacterium species reported lower levels of anxiety and improved mental outlook after two weeks, in comparison to placebo group. Another study indicated that probiotics might help reduce depressive symptoms by lowering cortisol levels and inflammatory markers in the body, which are often elevated in people with depression (Wallace & Milev, 2017). Additionally, emerging research suggests that probiotics can also enhance cognitive function. A study found that elderly participants who consumed probiotics showed improvements in cognitive tests, indicating that probiotics might help mitigate age-related cognitive decline (Akbari et al., 2016).

Further Evidence:

Omega-3 fatty acids showed significant improvement in mood disorders in a randomised, double-blind, placebo-controlled study (Freeman et al., 2010).
Probiotics reduced anxiety and depression scores in subjects with reduced urinary free cortisol (Messaoudi et al., 2011).
A meta-analysis confirmed the positive effects of omega-3 on depression, emphasising its role as an adjunctive therapy for mood disorders (Grosso et al., 2013).
A multistrain probiotic formula significantly reduced cognitive reactivity to depression in healthy young adults (Steenbergen et al., 2015).
Probiotics improved scores on the Beck Depression Inventory in a randomized, double-blind study (Akkasheh et al., 2016).
A new class of probiotics, known as psychbiotics, is being explored as a non-toxic intervention for psychiatric conditions, showing promising results in several clinical trials (Dinan et al., 2013).
Antioxidant therapy reduced oxidative stress and improved mood in patients with chronic fatigue syndrome (Maes et al., 2018).
Vitamin B12 supplementation improved mood and reduced symptoms of depression in older adults with B12 deficiency (Hintikka et al., 2003).
A combination of B vitamins (B6, B12, and folate) showed a reduction in depressive symptoms in a double-blind, placebo-controlled trial (Lewis et al., 2010).
High-dose B vitamin treatment was effective in reducing symptoms of depression and improving cognitive function in individuals with major depressive disorder (Young et al., 2017).

Conclusions

Omega-3, antioxidants, and Vitamin B represent key nutrients being explored as non-toxic interventions for mental health, with several clinical trials showing promising results in reducing symptoms of depression, anxiety, and cognitive decline.

Written by Weronika, Smart TMS Edinburgh practitioner