The bi-directional communication between the gut microbiome and the brain, commonly referred to as the gut-brain axis, is a complex biochemical pathway that helps regulate central nervous system homeostasis and digestive function. The gut-brain axis may influence antioxidative status, the inflammatory response, and mechanisms related to brain functioning and mood health. In addition, the activity of microbial metabolites that reside in the gut has been shown to play a role in neurocognitive health and mood. Research suggests that probiotic supplementation may help support aspects of the gut-brain axis such as supporting balanced moods and mental health.

A four-week, double-blind randomized control trial explored the potential impact of supplementation with several strains of Lactobacillus and Bifidobacterium on mood health. The authors associated increases in the genus Lactobacillus that were observed in the treatment group with improvements in certain parameters related to mood health, however, these data are preliminary and more research is needed before clinical conclusions can be made. Probiotic supplementation was also linked with improvements in biomarkers associated with gut microbiome health including species richness. 

A randomized placebo-controlled study explored the efficacy of probiotic supplementation in the presence of psychological stress and anxiety. The study involved supplementation with Lactobacillus plantarum P-8 for twelve weeks in adults experiencing psychological stress. Study results indicated that the abundance of certain microbial communities shifted in the treatment group but not in the placebo arm. Improvements in parameters related to stress and increases in microbial metabolite activity were also noted in the treatment group. 

A recently published review explored the impact of Bifidobacterium and Lactobacillus strains, both individually administered and in combination, on mood health. Improvements associated with mood, quality of life, inflammation, brain function, and gut health were reported. These include improvements in brain-derived neurotrophic factor (BDNF) levels, interleukin (IL)-6 activity, limbic reactivity, and high-sensitivity C-reactive protein (hsCRP) levels. 

Research suggests that a Mediterranean-type diet may also play a supportive role in gut-brain health. The dietary intake of omega-3 polyunsaturated fatty acids (PUFAs) has been associated with a protective effect on the risk of certain mood disorders. It has also been shown to help lower the production of pro-inflammatory cytokines such as IL-6 and IL-1β, upregulate BDNF levels, and may help support the maintenance of the hypothalamic-pituitary-adrenal axis. In clinical studies, adherence to the Mediterranean diet has been linked to improvements in mood health, cognitive function, and quality of life. 

Evidence indicates that adherence to the Mediterranean diet may also help support a healthy gut microbiome. Clinical studies have associated Mediterranean diet adherence with a healthy Firmicutes-Bacteroidetes ratio, increased levels of microbial metabolites including short-chain fatty acids (SCFAs), and several health-supportive microbial genera. More research is needed, however, before a clinical connection between the Mediterranean diet and gut microbial health can be made.

Evidence suggests that certain lifestyle factors and probiotic supplementation such as certain Lactobacillus and Bifidobacterium strains may help support the gut-brain axis. They may also help support mood health, a normal response to psychological stress, and a normal inflammatory response. 

By Dr. C. Ambrose, ND, MAT