PROBIOTICS AND GUT BRAIN AXIS | After Nutrition

PROBIOTICS AND GUT BRAIN AXIS

The understanding that intestinal health influences overall health dates back thousands of years. Long before the era of gene sequencing and metagenomics, Hippocrates stated that “all disease begins in the gut.”
Modern science has now unveiled that the gastrointestinal tract is inhabited by trillions of microorganisms—collectively called the human microbiome. These organisms interact with the intestinal mucosa as well as the immune, endocrine, and nervous systems.
This multisystem web of communication has been termed the “gut-brain axis.” Its mediators include neurotransmitters, hormones, peptides, cytokines, chemokines, and byproducts of bacterial metabolism.

Science has revealed intricate details about the human microbiome and the gut-brain axis, but many questions remain. For instance, how does the microbiome affect a person’s mood? If changes in gut microbes accompany changes in emotions, which comes first? Can we modify the microbiome to support mental and emotional health? Where do probiotic supplements come into play?

Researchers have examined many of these questions in recent years. Results from human clinical trials are beginning to provide practical understanding of the microbiome and the gut brain axis. Here’s a look at key studies that offer insights into probiotic supplementation to support mood, stress, and cognition.

PROBIOTICS AND MOOD
There are many proposed mechanisms by which probiotics might influence mood. Researchers have found that gut microbiota can modulate serotonin function, support healthy inflammatory pathways, or communicate directly with the limbic system via the vagus nerve.
Researchers have evaluated whether probiotics offer mood support. In a 2016 study published in Nutrients, 40 participants were randomized to take a daily probiotic capsule or a placebo for eight weeks. The probiotic capsule consisted of three viable and freeze-dried strains: Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum. Results showed that the subjects taking the multispecies probiotic experienced a healthy mood in contrast to placebo.
Many women experience mood changes during the postpartum period due to hormonal changes, so researchers assessed whether probiotics would support a healthy mood during this time. In a 2017 study published in EBioMedicine, 423 pregnant women were randomized to take Lactobacillus rhamnosus HN001 from 16 weeks of gestation until six months postpartum. Based on questionnaires completed by the women during the postpartum period, those who were taking the probiotic experienced healthy coping and stress response and a healthy mood. These results are significant, because probiotic use is safe during pregnancy and postpartum.
Probiotics may also support a person’s cognitive reaction to mood changes. Why is this important? Cognitive reactivity to mood increases vulnerability to dysfunctional thoughts and behaviors.
In a 2015 study published in Brain, Behavior, and Immunity, 40 healthy participants were randomized to take a multispecies probiotic product called Ecologic Barrier, or a placebo. After four weeks of supplementation, those taking the probiotic experienced less cognitive reactivity to their mood.

PROBIOTICS AND MOOD
There are many proposed mechanisms by which probiotics might influence mood. Researchers have found that gut microbiota can modulate serotonin function, support healthy inflammatory pathways, or communicate directly with the limbic system via the vagus nerve.
Researchers have evaluated whether probiotics offer mood support. In a 2016 study published in Nutrients, 40 participants were randomized to take a daily probiotic capsule or a placebo for eight weeks. The probiotic capsule consisted of three viable and freeze-dried strains: Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum. Results showed that the subjects taking the multispecies probiotic experienced a healthy mood in contrast to placebo.
Many women experience mood changes during the postpartum period due to hormonal changes, so researchers assessed whether probiotics would support a healthy mood during this time. In a 2017 study published in EBioMedicine, 423 pregnant women were randomized to take Lactobacillus rhamnosus HN001 from 16 weeks of gestation until six months postpartum. Based on questionnaires completed by the women during the postpartum period, those who were taking the probiotic experienced healthy coping and stress response and a healthy mood. These results are significant, because probiotic use is safe during pregnancy and postpartum.
Probiotics may also support a person’s cognitive reaction to mood changes. Why is this important? Cognitive reactivity to mood increases vulnerability to dysfunctional thoughts and behaviors.
In a 2015 study published in Brain, Behavior, and Immunity, 40 healthy participants were randomized to take a multispecies probiotic product called Ecologic Barrier, or a placebo. After four weeks of supplementation, those taking the probiotic experienced less cognitive reactivity to their mood.

PROBIOTICS AND STRESS
One new area of research has been whether probiotic supplementation influences the stress response. Probiotics might interact with the stress response because of the intricate communication networks between the gut, the sympathetic nervous system, and the hypothalamic-pituitary-adrenal axis.
In a study published in 2016 in Translational Psychology, researchers evaluated whether consumption of the probiotic Bifidobacterium longum 1714 affected stress response or brain-activity patterns in healthy volunteers. Participants completed neurocognitive tests and stress tests before and after taking the probiotic for four weeks. Results showed that consumption of B. longum 1714 was positively associated with support for stress response and memory.*
In a study published in 2017 in the Journal of Functional Foods, daily intake of Lactobacillus gasseri CP2305 supported mental, physical, and sleep quality among Japanese medical students.

PROBIOTICS AND COGNITION
As with mood and stress, many different mechanisms might explain how probiotics influence cognition. It may be that probiotics indirectly support cognition by supporting healthy inflammatory pathways or healthy glucose metabolism.
In a 2016 study published in Frontiers in Aging Neuroscience, researchers evaluated the effects of probiotic supplementation on the MMSE. Sixty participants were randomized to drink either a placebo or milk containing Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum, and Lactobacillus fermentum probiotics for 12 weeks. Results showed that the probiotic supplement had a positive effect on MMSE scores.
Last year (2020), a randomized clinical trial examining the impact of Lactobacillus rhamnosus GG probiotic supplementation on cognitive functioning in middle-aged and older adults was published in Neuropsychiatric Disease and Treatment. The outcome showed that supplementation supported healthy cognitive function in older adults.
This year (2021), a study on the effects of probiotic supplementation on cognitive health in older adults was published in the The Journals of Gerontology. Series A, Biological sciences and medical sciences. The goal of this randomized, controlled trial was to evaluate whether a probiotic combination of Bifidobacterium bifidum BGN4 and Bifidobacterium longum BORI would support cognition and mental health in older men and women.The primary outcomes of interest were healthy changes in cognition and mental health. A validated cognition test revealed a significant difference between the probiotic and placebo groups at week 12, with probiotics supporting mental flexibility.

EVOLVING SCIENCE
The science of understanding how probiotics relate to the gut-brain axis is still young and because this is an emerging field of research, most human studies have been small.
Our current knowledge of this subject may be limited, but it’s hard to deny that the relationship between the intestinal microbiome and mood is real and intriguing. Given that probiotics are generally a safe and tolerable supplement, they may be worth adding to your toolbox of supplements to support mental and emotional health.

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