Exploring the crucial link between nutrition and mental health, this review offers unique insights by addressing the ‘triple burden’ of malnutrition: undernutrition, overnutrition, and micronutrient deficiencies. We delve into the mechanisms of psychobiotics, including specific strains like Lactobacillus plantarum PS128 and Bifidobacterium longum 1714, and examine the impact of psychiatric medications on the gut microbiome, a critical factor often overlooked in traditional approaches.
Building upon recent clinical trials (Vicariotto et al., 2023; Ho et al., 2021), this analysis aims to advance integrated nutritional psychiatry strategies for mental disorder prevention and management. We focus on key nutritional components like omega-3 fatty acids, antioxidants, and probiotics for optimal brain health and psychological well-being. Furthermore, we explore emerging areas such as microalgae (Chlamydomonas reinhardtii) and astaxanthin, while also addressing the importance of public health nutrition policies, including Nutri-Score and fiscal measures, in shaping healthier dietary patterns.
1. Nutrition and mental health
Modern society faces a ‘triple burden’ of malnutrition: undernutrition, overnutrition, and micronutrient deficiencies, all of which are closely linked to mental health outcomes. A varied and balanced diet is crucial for maintaining psychological well-being and preventing psychiatric disorders:
• Diets rich in fruits, vegetables, whole grains, lean proteins, and healthy fats support brain function and emotional regulation.
• Omega-3 fatty acids, found in fatty fish and nuts, help maintain neuronal integrity and reduce inflammation.
• Antioxidants from fruits and vegetables combat oxidative stress, which is linked to neurodegenerative and psychiatric conditions.
Studies like the SMILES trial by Jacka et al., (2017) have demonstrated that dietary improvements can significantly reduce depressive symptoms, highlighting the therapeutic potential of nutrition in mental health care.
1.1. Obesity, overweight, and mental health
Obesity and overweight are significant risk factors for psychiatric conditions, including depression, anxiety, and eating disorders:
• Chronic low-grade inflammation associated with obesity disrupts the gut-brain axis, leading to neuroinflammation and altered neurotransmitter function.
• Obesity is often linked to metabolic conditions, such as type 2 diabetes and cardiovascular disease, which increase mental health risks.
A study by Luppino et al., (2010) found a bidirectional relationship between obesity and depression, with each condition exacerbating the other. Social stigma and discrimination faced by individuals with obesity contribute to low self-esteem and body dissatisfaction, worsening mental health outcomes and creating a vicious cycle.
1.2. Nutrient and micronutrient imbalances
Deficiencies in essential nutrients, such as B vitamins, zinc, magnesium, and omega-3 fatty acids, can significantly impact the nervous system and contribute to psychiatric disorders. Research suggests that targeted food supplementation can help improve mental health, particularly in conditions like depression and anxiety. For example:
• Compounds like S-adenosylmethionine (SAM), N-acetylcysteine, zinc, B vitamins, and omega-3 fatty acids play critical roles in maintaining psychological well-being.
• Imbalances in macronutrient and micronutrient intake, such as deficiencies in vitamin D and omega-3 fatty acids, can exacerbate mental health conditions.
2. Nutritional interventions with preventive potential
Nutritional psychiatry is exploring the preventive role of diet in mental health. Diets rich in omega-3 fatty acids, antioxidants, and micronutrients have been consistently linked to a reduced risk of developing mental disorders:
• omega-3 fatty acids are essential for brain function and have anti-inflammatory properties, which help alleviate depression and anxiety;
• antioxidants, including vitamins C and E, reduce oxidative stress, a major contributor to neurodegenerative and psychiatric conditions;
• micronutrients such as zinc, magnesium, and B vitamins support neurotransmitter synthesis and neural function, further supporting mental health.
Emerging evidence suggests that personalised nutrition, tailored to an individual’s genetic, metabolic, and microbiomic profile, may offer significant potential for preventing mental health disorders. This approach recognises the unique relationship between diet, gut microbiota, and the gut-brain axis, enabling more targeted and effective dietary interventions to optimise mental well-being.
3. The microbiome-gut-brain relationship
The idea that gut health is central to overall well-being is not new. As early as the 4th century BC, Hippocrates posited that diseases originate in the intestines. Modern science has validated this ancient wisdom, revealing the critical role of the gut microbiota in human health, including its influence on the central nervous system (CNS).
The gut microbiota, comprising trillions of microorganisms, and its collective genome, the microbiome, are key components of the gut-brain axis. This bidirectional communication pathway links the gut to cognitive and emotional centres in the brain, highlighting the profound impact of gut health on mental well-being.
The gut-brain axis is a complex network of nervous, endocrine, immune, and metabolic mechanisms, highlighting the connection between gut health and mental disorders. Dysbiosis, or microbial imbalance, can lead to increased intestinal permeability, inflammation, and oxidative stress, all of which are associated with psychiatric disorders such as depression, anxiety, and schizophrenia.
4. Psychoprotective food ingredients
Probiotics have emerged as a key area of interest in nutritional psychiatry. These beneficial microorganisms—found in certain foods like dairy, fermented products, and food supplements—play a crucial role in maintaining gut microbiota balance (eubiosis) and reducing dysbiosis.
Notably, psychobiotics (probiotics with demonstrated mental health benefits) exert their effects through mechanisms such as modulation of the hypothalamic-pituitary-adrenal (HPA) axis, immune response regulation, and production of neurohormones and neurotransmitters (Del Toro-Barbosa et al., 2020).
Prebiotics, non-digestible food components such as inulin and fructooligosaccharides, support gut health by promoting the growth of probiotics. Synbiotics, which combine both probiotics and prebiotics, offer a synergistic approach to enhancing gut microbiota, and their potential should also be explored.
5. The microbiome’s influence on nervous system activity
The gut microbiome influences numerous physiological processes, including immunomodulation, energy balance, and CNS electrophysiological activity. Dysbiosis can lead to increased intestinal permeability, allowing harmful metabolites and bacteria to enter the bloodstream. This condition, known as ‘leaky gut’, is associated with inflammation and oxidative stress, both of which are linked to psychiatric disorders such as depression and anxiety.
Recent studies have categorised the effects of microbiome alterations into three main areas:
• psychological effects. Bacterial metabolites, such as short-chain fatty acids (SCFAs), act as epigenetic modulators, influencing cognitive and emotional functions;
• systemic effects. The gut microbiota develops alongside the HPA axis, impacting glucocorticoid levels and inflammation. Elevated pro-inflammatory cytokines are strongly associated with psychiatric conditions like depression;
• neural effects. Gut inflammation disrupts tryptophan metabolism, reducing serotonin production. Neurotransmitters like GABA and glutamate, which regulate neural excitation and inhibition, are also affected. Additionally, Brain-Derived Neurotrophic Factor (BDNF), crucial for learning and memory, is often reduced in anxiety and depression but can be restored through antidepressant treatment.
6. Psychiatric medicines’ influence on gut flora
Conventional psychiatric medications, including antidepressants and antipsychotics, can disrupt gut flora, potentially worsening dysbiosis and impacting mental health:
• widely used antidepressants like fluoxetine (Prozac) and escitalopram may alter the gut microbiome;
• mood stabilisers such as valproate and lithium have been linked to increased Clostridium species;
• some antidepressants also inhibit Escherichia coli strains, further highlighting the complex interaction between psychiatric treatments and gut health.
Further studies are needed to identify the most effective probiotics for individuals on psychiatric medications, as part of an integrated approach to restore gut health and support overall mental well-being.
7. Psychobiotics: potential contributions to mental wellbeing
Psychobiotics, defined as probiotics or prebiotics with mental health benefits, are showing a promising role in contributing to mental wellbeing. These beneficial bacteria, primarily from the Bifidobacterium and Lactobacillus families, exert anxiolytic and antidepressant effects through mechanisms involving the enteric nervous system and immune system. Unlike pro-inflammatory bacteria, psychobiotics do not trigger significant immunological reactions, making them safe for long-term use.
7.1. Lactic acid bacteria and depression
A randomized, double-blind, placebo-controlled trial by Ho et al., (2021) investigated the effects of Lactobacillus plantarum PS128 (LP128) on mental health and sleep quality in 40 adults with self-reported insomnia. Participants took either LP128 or a placebo for 30 days, with assessments at baseline, day 15, and day 30.
While overall outcomes were comparable between groups, the LP128 group showed significant reductions in depressive symptoms (Beck Depression Inventory-II scores), fatigue levels, brainwave activity, and awakenings during deep sleep. These findings suggest that LP128 may help alleviate depression and improve sleep quality, warranting further research.
7.2. Bifidobacterium and stress reduction
Bifidobacterium supplementation has been shown to restore intestinal barrier integrity, reduce stress-induced inflammation, and improve cognitive function. Notably, Bifidobacterium longum 1714 was found to significantly reduce stress levels and improve memory in healthy volunteers, suggesting its potential to support mental health.
7.3. Maternal stress and infant microbiota
A randomised, double-blind, placebo-controlled trial by Slykerman et al., (2017) investigated the effects of Lactobacillus rhamnosus on postpartum depression and anxiety. Results showed that women who received HN001 had significantly lower depression and anxiety scores than the placebo group, suggesting its potential for supporting maternal mental health.
Similarly, Vicariotto et al., (2023) conducted a randomized, double-blind, placebo-controlled study on the impact of Limosilactobacillus reuteri PBS072 and Bifidobacterium brevis BB077 in postpartum women. Their findings show that probiotic supplementation during the first trimester postpartum may enhance mood, self-confidence, and breastfeeding success.
8. The gut microbiome in severe psychiatric disorders
The gut microbiome plays a critical role in severe psychiatric disorders like bipolar disorder and schizophrenia. Dysbiosis has been linked to the severity, symptoms, and treatment responses of these conditions. This growing understanding highlights the potential of microbial-focused therapies, including dietary changes and psychobiotics, to complement traditional treatments.
8.1. Bipolar disorder
Research has revealed distinct gut microbiota profiles in patients with bipolar disorder (BD), characterised by higher abundances of Actinobacteria and lower abundances of Faecalibacterium and Ruminococcaceae. These microbial alterations are thought to contribute to the disorder’s pathophysiology, potentially through mechanisms involving inflammation, oxidative stress, and impaired gut-brain axis communication.
8.2. Schizophrenia
In schizophrenia, gut microbiota dysbiosis is increasingly recognised as a contributing factor to the disorder’s onset and progression. Studies have shown that patients with first-episode schizophrenia psychosis have significantly lower levels of Bifidobacterium and Lactobacillus, two genera known for their beneficial effects on gut health and mental well-being.
9. Interim conclusions
Addressing the ‘triple burden’ of malnutrition—undernutrition, overnutrition, and micronutrient deficiencies—requires robust public health nutrition policies. Implementation of front-of-pack nutrition labelling (FOPNL) like Nutri-Score and strategic fiscal measures are crucial to mitigate the impact of obesogenic diets on both physical and mental health.
On an individual level, integrated nutritional psychiatry strategies, focusing on psychobiotics, omega-3 fatty acids, and antioxidants, including astaxanthin, offer significant potential. Specifically, exploring the mechanisms of strains like Lactobacillus plantarum PS128 and Bifidobacterium longum 1714, and understanding the impact of psychiatric medications on the gut microbiome, are essential for personalized interventions.
Further research should prioritize the efficacy of microalgae such as Chlamydomonas reinhardtii and the detailed understanding of the gut-brain axis. Public support is vital to advance these integrated approaches, moving beyond traditional treatments to fully leverage the potential of nutritional interventions in mental disorder prevention and management. This includes addressing the complex interactions between diet, gut health, and brain health to optimize psychological well-being across populations.
Dario Dongo
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Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
