The science behind the gut-brain axis

Introduction

In the fast-paced world we live in, maintaining optimal health and wellbeing is a constant challenge.

 

The intricate connection between the gut and the brain has been gaining prominence in recent years, revealing the potential for comprehensive solutions that address both physical and mental aspects of health.

 

Our revolutionary superblend is meticulously crafted, combining a unique blend of scientifically-backed ingredients to optimise physical and mental functioning to elevate our everyday.

 

The gut-bain axis is a bi-directional communication network connecting the gastrointestinal tract to the central nervous system.

 

Emerging research suggests that the microbiota in the gut plays a pivotal role in influencing cognitive functions, mood, and overall wellbeing. Our gut-brain superblend leverages this connection, promoting a harmonious balance between the gut and the brain.

Poster

A bi-directional relationship

The brain has a direct effect on the stomach and intestines. For example, the very thought of eating can release the stomach's juices before food gets there. This connection goes both ways. A troubled intestine can send signals to the brain, just as a troubled brain can send signals to the gut. Therefore, a person's stomach or intestinal distress can be the cause or the product of anxiety, stress, or depression. That's because the brain and the gastrointestinal system are intimately connected.

 

(Harvard Health, 2023)

Harmonising the body and the mind

At Thryve, we're dedicated to enhancing both brain and gut health, strategically optimising the bidirectional communication within the gut-brain axis.

 

By synergising the positive impacts that each element brings individually, we aim to deliver unparalleled benefits for you, including enhanced cognitive function, improved mood regulation, sustained energy levels, optimised digestive health, better sleep quality, increased emotional resilience, potential support for weight management, reduced inflammation, and improved immune function.

 

This synergistic relationship between the gut and the brain fosters an overall sense of wellbeing, contributing to a positive outlook on life and daily activities.

Key ingredients and their benefits, according to research

L-Theanine

Scientific studies have consistently demonstrated the relaxation-promoting effects of L-theanine, an amino acid found naturally in green tea (Kimura et al., 2007). Known for its anti-anxiety properties, L-theanine aids in reducing stress and anxiety levels, thereby enhancing overall mood (Kim et al., 2019). This compound acts as an anxiolytic, facilitating feelings of calmness and improved sleep quality without causing daytime drowsiness (Rao et al., 2015). Moreover, L-theanine has been shown to benefit mental health by alleviating stress-related symptoms and cognitive impairments (Hidese et al., 2019). It also counteracts the sleep disturbances induced by caffeine consumption (Jang et al., 2012) and regulates brain electrochemical activity (Dasdelen et al., 2022). Studies further suggest that L-theanine possesses neuroprotective properties and enhances cognitive function (Nathan et al., 2006). When combined with caffeine, L-theanine not only improves cognitive performance but also enhances attention, working memory, and executive functions (Baba et al., 2021; Haskell et al., 2008; Owen et al., 2008).

 

Lion's Mane

Lion's Mane mushroom has garnered attention for its potential neuroprotective properties, stimulating the growth of nerve cells and potentially enhancing cognitive function and memory (Mori et al., 2008). Chronic supplementation with Lion's Mane mushroom has demonstrated cognitive and mood-enhancing effects, suggesting its potential as a therapeutic agent (Docherty et al., 2023). Research indicates that Lion's Mane mushroom may improve cognitive function, short-term memory, and behavioral outcomes, making it a promising intervention for conditions like Alzheimer's disease (Datsen, 2022). Moreover, Lion's Mane mushroom exhibits antidepressant effects by promoting neurogenesis and reducing neuroinflammation, offering potential as an alternative treatment for depression (Chong et al., 2021). With consistent use, Lion's Mane mushroom has shown anxiolytic and antidepressant-like effects, reducing anxiety and depressive behaviors (Ryu et al., 2018). Additionally, Lion's Mane mushroom has demonstrated the ability to enhance recognition memory and induce neurogenesis in aging individuals, potentially mitigating cognitive decline (Ratto et al., 2019). Its consumption has also been associated with mood enhancements and improved cognitive function across different age groups (Cha et al., 2024).

Green Coffee Bean

Green coffee beans, rich in chlorogenic acids, are recognized for their antioxidant properties, which contribute to enhanced energy levels and potential improvements in cognitive function and mood (Cho et al., 2010). Studies have demonstrated that green coffee enriched with chlorogenic acids can positively impact higher-level mood and attention processes, particularly among elderly individuals, indicating its potential as a cognitive enhancer (Cropley et al., 2012). Moreover, research suggests that green coffee offers various health benefits and may support cognitive functions, underscoring its economic importance and therapeutic potential (Bosso et al., 2023). The chlorogenic acids present in green coffee may also play a role in reducing the risk of neurodegenerative conditions, suggesting a potential neuroprotective effect (Heitman & Ingram, 2017).

Bacopa Monnieri

Bacopa monnieri, a staple in Ayurvedic medicine for cognitive enhancement, has garnered scientific attention for its memory-enhancing and stress-reducing properties (Stough, 2001). Research indicates that Bacopa monnieri can improve attention, cognitive processing, and working memory, contributing to overall cognitive function (Peth-Nui et al., 2012). Furthermore, studies have demonstrated that Bacopa monnieri supplementation increases emotional well-being and general health, further supporting its cognitive benefits (Lopresti et al., 2021). With its neuroprotective effects, Bacopa monnieri enhances learning and memory processes, providing a boost to cognitive function (Sukumaran et al., 2019). Additionally, Bacopa monnieri has been found to significantly enhance memory acquisition and retention, contributing to improved cognitive performance (Morgan & Stevens, 2010). It also shows promise in improving working memory and information processing, further bolstering cognitive abilities (Stough et al., 2008). Moreover, Bacopa monnieri supplementation may help slow the decline of language and attention in dementia, suggesting potential therapeutic applications in cognitive decline (Delfan et al., 2024).

 

Phosphatidylserine

Phosphatidylserine, a vital component of cell membranes, plays a crucial role in supporting cognitive functions across various domains, including memory, learning, attention, concentration, problem-solving, logical reasoning, language, communication, and locomotor functions, particularly rapid reactions and reflexes (Glade & Smith, 2015). Scientific studies have shown that supplementation with phosphatidylserine significantly enhances short-term memory, attention, and impulsivity in children with ADHD, indicating its potential as a cognitive aid (Hirayama et al., 2014). Moreover, phosphatidylserine has been found to improve memory functions, particularly in the early stages of dementia, suggesting its potential therapeutic use in cognitive decline (Kato-Kataoka et al., 2010).

Citicoline

Citicoline, a compound that serves as a precursor to acetylcholine, a key neurotransmitter involved in cognitive function, has garnered attention for its potential benefits in memory enhancement and neuroprotection (Silveri et al., 2008). As a dopaminergic agent, citicoline influences the neurotransmitter dopamine and related nervous system components, leading to improvements in attention, alertness, and antioxidant activity (Tabassum et al., 2008). Studies have demonstrated citicoline's ability to significantly enhance story recall in normally aging older adults, indicating its positive impact on memory (Spiers et al., 1996). Additionally, citicoline has shown promise in improving depressive symptoms in individuals with depression and substance dependence (Brown & Gabrielson, 2012). Furthermore, research suggests that citicoline may enhance learning and memory performance, exert neuroprotective effects, and potentially halt the progression of cognitive decline in patients with vascular cognitive impairment and degenerative dementias (Secades, 2019). Citicoline has also been investigated as an effective adjunctive therapy for major depressive disorder (Roohi-Azizi et al., 2017) and has shown potential in increasing dopamine receptor densities and ameliorating memory impairment (Pranav, 2013).

Rhodiola Rosea

Rhodiola Rosea, renowned for its adaptogenic properties, aids the body in adapting to stress, offering relief from mental fatigue and enhancing overall cognitive performance (Spasov et al., 2000). Extensive research has underscored its efficacy in addressing a spectrum of conditions including anxiety, depression, fatigue, and burnout, as well as cardiovascular and reproductive dysfunctions (Ivanova Stojcheva & Quintela, 2022). Recognized by the Herbal Medicinal Product Committee for stress management, Rhodiola Rosea influences stress hormone release while bolstering energy metabolism (Anghelescu et al., 2018). Widely used to stimulate the nervous system, alleviate depression, enhance work performance, combat fatigue, and prevent altitude sickness, Rhodiola Rosea emerges as a promising treatment for anxiety, stress, and fatigue, alongside its potential to uplift mood, augment mental performance, and enhance cognition (Khanum et al., 2006; Lewis et al., 2021). Evidence suggests significant enhancements in attention, speed, and accuracy of mental performance with Rhodiola Rosea supplementation (Aslanyan et al., 2010). Moreover, sustained improvements in both physical and cognitive performance have been observed over 12 weeks of Rhodiola Rosea supplementation (Fintelmann et al., 2007). Studies have reported notable reductions in anxiety, stress, anger, depression, and confusion, coupled with enhanced overall mood after just 14 days of Rhodiola Rosea usage (Cropley et al., 2015). Additionally, improvements in fatigue indicators, including short-term memory, perception speed, and attention capacity, have been demonstrated within a two-week period (Darbinyan et al., 2000).

Cordyceps Mushroom

Cordyceps, renowned for its energy-boosting properties, has been linked to enhanced exercise performance and increased energy levels, making it a valuable aid in combating fatigue and improving endurance (Koh et al., 2003). Moreover, research suggests that Cordyceps enhances learning and memory functions by shielding the nervous system from oxidative damage (Yuan et al., 2018). With its anti-inflammatory and antioxidant effects, Cordyceps holds promise in managing depression (Lin et al., 2021). Furthermore, Cordyceps exhibits a range of beneficial properties, including antioxidant, anti-inflammatory, and anti-apoptotic activities, making it a potential candidate for the treatment of neurodegenerative disorders (Sharma et al., 2023). Studies have shown significant improvements in daytime functioning capacity among individuals experiencing depression with insomnia after Cordyceps supplementation (Zhou et al., 2021).

Inulin (Prebiotic)

Inulin, recognized as a prebiotic, acts as a vital fuel source for beneficial gut bacteria, promoting improved gut health and enhanced digestion (Roberfroid, 2007). Furthermore, supplementation with inulin has been associated with elevated levels of happiness, reduced indigestion, and decreased hunger levels, alongside enhanced cognitive performance on tasks related to recognition memory and free recall (Smith, Sunderland, and Hewlett, 2015). Studies also indicate that inulin supplementation exerts favorable effects on mood and cognition (Leyrolle et al., 2021), while enhancing cognitive performance on episodic memory tasks such as free recall and recognition memory (Chunchai et al., 2018). Recent research underscores the importance of prebiotic intake in increasing concentrations of beneficial gut bacteria, subsequently impacting communication along the gut-brain axis to enhance brain function, including learning, working memory, and behavior (Serra et al., 2019).

Bifidobacterium Longum, Lactobacillus Acidophilus and Lactobacillus Rhamnosus (Probiotics)

Probiotics are essential for gut health, influencing the gut-brain axis and offering benefits for mood regulation and cognitive function (Hill et al., 2014). Studies highlight the positive impact of Bifidobacterium Longum on mental flexibility, stress reduction, and gut microbiota enhancement, particularly in older adults (Kim et al., 2021; Allen et al., 2016; Wang et al., 2019). Additionally, Lactobacillus Acidophilus shows promise in memory improvement for individuals with diabetes and alleviating depressive symptoms (Davari et al., 2013; Akkasheh et al., 2016). Notably, Lactobacillus Rhamnosus demonstrates efficacy in reducing anxiety, stress, and depression-related behaviors (Bravo et al., 2011; Smith et al., 2014). Psychobiotics, a novel category of microorganisms, exhibit anxiolytic and antidepressant effects by influencing bacteria-brain relationships through various communication channels (Casertano et al., 2021; Sarkar et al., 2016). Furthermore, probiotic interventions, including mixed strains, show promising results in reducing reactivity to sad moods and improving memory and anxiety (Steenbergen et al., 2015; Eastwood et al., 2021).

References

L-Theanine:

Kimura, K., Ozeki, M., Juneja, L. R., & Ohira, H. (2007). L-Theanine reduces psychological and physiological stress responses.

Kim, S., Jo, K., Hong, K., Han, S. H., & Suh, H. J. (2019). GABA and L-theanine mixture decreases sleep latency and improves NREM sleep.

Rao, T. P., Ozeki, M., & Juneja, L. R. (2015). In Search of a Safe Natural Sleep Aid.

Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial.

Jang, H. S., Jung, J. Y., Jang, I. S., Jang, K. H., Kim, S. H., Ha, J. H., ... & Lee, M. G. (2012). L-theanine partially counteracts caffeine-induced sleep disturbances in rats.

Dasdelen, M. F., Er, S., Kaplan, B., Celik, S., Beker, M. C., Orhan, C., ... & Kilic, E. (2022). A novel theanine complex, Mg-L-Theanine improves sleep quality via regulating brain electrochemical activity.

Hidese, S., Ota, M., Wakabayashi, C., et al. (2017). Effects of chronic L-theanine administration in patients with major depressive disorder: an open-label study.

Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., & Scholey, A. B. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood.

Nathan, P. J., Lu, K., Gray, M., & Oliver, C. (2006). The Neuropharmacology of L-Theanine (N-Ethyl-L-Glutamine).

Owen, G. N., Parnell, H., De Bruin, E. A., & Rycroft, J. A. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood.

Baba, Y., Inagaki, S., Nakagawa, S., Kaneko, T., Kobayashi, M., & Takihara, T. (2021). Effects of L-theanine on cognitive function in middle-aged and older subjects: a randomized placebo-controlled study.

Lion's Mane:

Mori, K., Obara, Y., Hirota, M., Azumi, Y., Kinugasa, S., & Inatomi, S. (2008). Nerve growth factor-inducing activity of Hericium erinaceus in 1321N1 human astrocytoma cells.

Docherty, S., Doughty, F. L., & Smith, E. F. (2023). The Acute and Chronic Effects of Lion’s Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults: A Double-Blind, Parallel Groups, Pilot Study.

Datsen, S. (2022). Lion’s mane mushroom: A fungus to remember, a novel venture into dementia therapy.

Chong, P. S., Poon, C. H., Roy, J., Tsui, K. C., Lew, S. Y., Phang, M. W. L., ... & Lim, L. W. (2021). Neurogenesis-dependent antidepressant-like activity of Hericium erinaceus in an animal model of depression.

Skubel, T., Budzyńska, J., Czarnota, J., Dobrzyński, M., Rybak, N., & Dudek, I. (2022). Therapeutic potential of Lion's Mane (Hericium erinaceus) in neurological and cognitive disorders-a review of the literature.

Ryu, S., Kim, H. G., Kim, J. Y., Kim, S. Y., & Cho, K. O. (2018). Hericium erinaceus extract reduces anxiety and depressive behaviors by promoting hippocampal neurogenesis in the adult mouse brain.

Ratto, D., Corana, F., Mannucci, B., Priori, E. C., Cobelli, F., Roda, E., ... & Rossi, P. (2019). Hericium erinaceus improves recognition memory and induces hippocampal and cerebellar neurogenesis in frail mice during aging.

Saitsu, Y., Nishide, A., Kikushima, K., Shimizu, K., & Ohnuki, K. (2019). Improvement of cognitive functions by oral intake of Hericium erinaceus.

Cha, S., Bell, L., Shukitt-Hale, B., & Williams, C. M. (2024). A review of the effects of mushrooms on mood and neurocognitive health across the lifespan.

Green Coffee Bean:

Cho, A. S., Jeon, S. M., Kim, M. J., Yeo, J., Seo, K. I., Choi, M. S., & Lee, M. K. (2010). Chlorogenic acid exhibits anti-obesity property and improves lipid metabolism in high-fat diet-induced-obese mice.

Cropley, V., Croft, R., Silber, B., Neale, C., Scholey, A., Stough, C., & Schmitt, J. (2012). Does coffee enriched with chlorogenic acids improve mood and cognition after acute administration in healthy elderly? A pilot study.

Bosso, H., Barbalho, S. M., de Alvares Goulart, R., & Otoboni, A. M. M. B. (2023). Green coffee: economic relevance and a systematic review of the effects on human health.

Heitman, E., & Ingram, D. K. (2017). Cognitive and neuroprotective effects of chlorogenic acid.

Bacopa Monnieri:

Stough, C. (2001). Bacopa monnieri: A review of its effects on cognitive function.

Stough, C., Lloyd, J., Clarke, J., Downey, L. A., Hutchison, C. W., Rodgers, T., & Nathan, P. J. (2001). The chronic effects of an extract of Bacopa monniera (Brahmi) on cognitive function in healthy human subjects.

Peth-Nui, T., Wattanathorn, J., Muchimapura, S., Tong-Un, T., Piyavhatkul, N., Rangseekajee, P., ... & Vittaya-Areekul, S. (2012). Effects of 12-week Bacopa monnieri consumption on attention, cognitive processing, working memory, and functions of both cholinergic and monoaminergic systems in healthy elderly volunteers.

Lopresti, A. L., Smith, S. J., Ali, S., Metse, A. P., Kalns, J., & Drummond, P. D. (2021). Effects of a Bacopa monnieri extract (Bacognize®) on stress, fatigue, quality of life and sleep in adults with self-reported poor sleep: A randomised, double-blind, placebo-controlled study.

Sukumaran, N. P., Amalraj, A., & Gopi, S. (2019). Neuropharmacological and cognitive effects of Bacopa monnieri (L.) Wettst–A review on its mechanistic aspects.

Morgan, A., & Stevens, J. (2010). Does Bacopa monnieri improve memory performance in older persons? Results of a randomized, placebo-controlled, double-blind trial.

Stough, C., Downey, L. A., Lloyd, J., Silber, B., Redman, S., Hutchison, C., ... & Nathan, P. J. (2008). Examining the nootropic effects of a special extract of Bacopa monniera on human cognitive functioning: 90 day double‐blind placebo‐controlled randomized trial.

Delfan, M., Kordestani-Moghaddam, P., Gholami, M., Kazemi, K., & Mohammadi, R. (2024). Evaluating the effects of Bacopa monnieri on cognitive performance and sleep quality of patients with mild cognitive impairment: A triple-blinded clinical trial.

Phosphatidylserine:

Glade, M. J., & Smith, K. (2015). Phosphatidylserine and the human brain.

Hirayama, S., Terasawa, K., Rabeler, R., Hirayama, T., Inoue, T., Tatsumi, Y., ... & Jäger, R. (2014). The effect of phosphatidylserine administration on memory and symptoms of attention‐deficit hyperactivity disorder: A randomized, double‐blind, placebo‐controlled clinical trial.

Kato-Kataoka, A., Sakai, M., Ebina, R., Nonaka, C., Asano, T., & Miyamori, T. (2010). Soybean-derived phosphatidylserine improves memory function of the elderly Japanese subjects with memory complaints.

Citicoline:

Silveri, M. M., Dikan, J., Ross, A. J., Jensen, J. E., Kamiya, T., Kawada, Y., ... & Renshaw, P. F. (2008). Citicoline enhances frontal lobe bioenergetics as measured by phosphorus magnetic resonance spectroscopy.

Tabassum, N., Rasool, S., Malik, Z. A., & Ahmad, F. (2012). Natural cognitive enhancers.

Spiers P.A., Myers D., Hochanadel G.S., Lieberman H.R., Wurtman R.J. (1996). Citicoline improves verbal memory in aging.

Brown, E. S., & Gabrielson, B. (2012). A randomized, double-blind, placebo-controlled trial of citicoline for bipolar and unipolar depression and methamphetamine dependence.

Secades, J. J. (2019). Citicoline in the treatment of cognitive impairment.

Roohi-Azizi, M., Arabzadeh, S., Amidfar, M., Salimi, S., Zarindast, M. R., Talaei, A., & Akhondzadeh, S. (2017). Citicoline combination therapy for major depressive disorder: a randomized, double-blind, placebo-controlled trial.

Joshi Pranav, C. (2013). A review on natural memory enhancers (Nootropics).

Rhodiola Rosea:

Spasov, A. A., Wikman, G. K., Mandrikov, V. B., Mironova, I. A., & Neumoin, V. V. (2000). A double-blind, placebo-controlled pilot study of the stimulating and adaptogenic effect of Rhodiola rosea SHR-5 extract on the fatigue of students caused by stress during an examination period with a repeated low-dose regimen.

Ivanova Stojcheva, E., & Quintela, J. C. (2022). The effectiveness of Rhodiola rosea L. preparations in alleviating various aspects of life-stress symptoms and stress-induced conditions—encouraging clinical evidence.

Anghelescu, I. G., Edwards, D., Seifritz, E., & Kasper, S. (2018). Stress management and the role of Rhodiola rosea: a review.

Khanum, F., Bawa, A. S., & Singh, B. (2005). Rhodiola rosea: a versatile adaptogen.

Lewis, J. E., Poles, J., Shaw, D. P., Karhu, E., Khan, S. A., Lyons, A. E., ... & McDaniel, H. R. (2021). The effects of twenty-one nutrients and phytonutrients on cognitive function: A narrative review.

Darbinyan V, Kteyan A, Panossian A, Gabrielian E, Wikman G, Wagner H. (2000). Rhodiola rosea in Stress Induced Fatigue--a Double Blind Cross-over Study of a Standardized Extract shr-5 with a Repeated Low-dose Regimen on the Mental Performance of Healthy Physicians during Night Duty.

Cropley M, Banks AP, Boyle J. (2015). The Effects of Rhodiola rosea L. Extract on Anxiety, Stress, Cognition and other Mood Symptoms.

Fintelmann V, Gruenwald J. (2007). Efficacy and Tolerability of a Rhodiola rosea Extract in Adults with Physical and Cognitive Deficiencies.

Aslanyan G, Amroyan E, Gabrielyan E, Nylander M, Wikman G, Panossian A. (2010). Double-blind, Placebo-controlled, Randomised Study of Single Dose Effects of Adapt-232 on Cognitive Functions.

Inulin:

Roberfroid, M. B. (2007). Inulin-type fructans: functional food ingredients.

Smith, A. P., Sutherland, D., & Hewlett, P. (2015). An investigation of the acute effects of oligofructose-enriched inulin on subjective wellbeing, mood and cognitive performance.

Leyrolle, Q., Cserjesi, R., Mulders, M. D., Zamariola, G., Hiel, S., Gianfrancesco, M. A., ... & Delzenne, N. M. (2021). Prebiotic effect on mood in obese patients is determined by the initial gut microbiota composition: a randomized, controlled trial.

Chunchai T, Thunapong W, Yasom S, Wanchai K, Eaimworawuthikul S, Metzler G, Lungkaphin A, Pongchaidecha A, Sirilun S, Chaiyasut C. (2018). Decreased microglial activation through gutbrain axis by prebiotics, probiotics, or synbiotics effectively restored cognitive function in obese-insulin resistant rats.

Serra, M. C., Nocera, J. R., Kelleher, J. L., & Addison, O. (2019). Prebiotic intake in older adults: effects on brain function and behavior.

Bifidobacterium Longum, Lactobacillus Acidophilus, and Lactobacillus Rhamnosus (Probiotics)

Hill, C., et al. (2014). The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic.

Kim, C. S., et al. (2021). Probiotic supplementation improves cognitive function and mood with changes in gut microbiota in community-dwelling older adults: a randomized, double-blind, placebo-controlled, multicenter trial.

Allen, A. P., et al. (2016). Bifidobacterium longum 1714 as a translational psychobiotic: modulation of stress, electrophysiology and neurocognition in healthy volunteers.

Wang, H., et al. (2019). Bifidobacterium longum 1714™ strain modulates brain activity of healthy volunteers during social stress.

Davari, S., et al. (2013). Probiotics treatment improves diabetes-induced impairment of synaptic activity and cognitive function: behavioral and electrophysiological proofs for microbiome–gut–brain axis.

Akkasheh, G., et al. (2016). Clinical and metabolic response to probiotic administration in patients with major depressive disorder: a randomized, double-blind, placebo-controlled trial.

Bravo, J. A., et al. (2011). Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve.

Eastwood, J., et al. (2021). The effect of probiotics on cognitive function across the human lifespan: A systematic review.

Casertano, M., et al. (2022). Psychobiotics, gut microbiota and fermented foods can help preserving mental health.

Steenbergen, L., et al. (2015). A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood.

Smith, C. J., et al. (2014). Probiotics normalize the gut-brain-microbiota axis in immunodeficient mice.