Psychobiotics: The Gut-Brain Connection

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There is a new and exciting branch of medicine studying the connection known as the “gut-brain axis.” It’s gaining momentum in the medical community because of the far-reaching effects gut health can have on the rest of your body. Imagine that the health of your gut could affect your brain health, and vice versa. Pretty cool, right? 

You’re probably already aware that probiotics support your gut in many ways. You may be eating foods rich in live bacteria or yeasts such as:

  • Kimchi
  • Sauerkraut
  • Miso
  • Beet kvass
  • Kefir
  • Yogurt
  • Pickled vegetables.

Or, maybe you’re taking probiotics on a regular basis. Either way, you are helping to create a healthy terrain, so to speak, by enriching the gut microbiome with health-promoting bacteria and yeasts. 

What Exactly Are Psychobiotics? 

The World Health Organization defines probiotics as “live micro-organisms that when ingested in adequate amounts confer a health benefit to the host.”  The probiotics you are most likely familiar with are Lactobacillus and Bifidobacteria since many foods and probiotics contain these two strains. Most of the research on probiotics has been focused on gut-related conditions like irritable bowel syndrome (IBS), or common gastrointestinal symptoms such as gas, bloating, abdominal discomfort, or constipation. But newer research, including mice and a few human studies, shows that some probiotics may in fact affect the brain. 

This is where psychobiotics come into play. Psychobiotics are defined as a type of probiotic or prebiotic that when ingested in adequate amounts provides mental health benefits. In other words, think of psychobiotics as substances (pro and pre-biotics) that affect mood or cognition.  

The understanding of psychobiotics is a relatively new phenomenon as the term was coined in 2012 by Professor Ted Dinan at the University College Cork in Ireland.   He originally identified probiotics as psychobiotics, but newer research is suggesting that prebiotics are under this umbrella as well, so for the purpose of this article I’ll refer to psychobiotics as pro- and prebiotics. 

How Do Probiotics and Prebiotics Affect Brain Function and Mental Health?

In order to understand how psychobiotics affect brain health, it’s helpful to be familiar with the gut-brain axis and how this connection is related to gut flora. We know that the gut and brain communicate and are connected through the following pathways and mechanisms:

  • Enteric nervous system, including the vagus nerve (the gut nervous system)
  • Signaling neurotransmitters
  • The gut immune system

We also know that gut flora are really key regulators in this gut-brain axis as they help modulate the bi-directional flow of information between the gut and the brain.

It appears through some studies on mice that certain strains of probiotics can temper the stress response. What this means is that probiotics can help modulate the hypothalamic adrenal (HPA) axis by decreasing production of cortisol and norepinephrine levels, which can have pro-cognitive and anti-stress effects. 

Human Studies on Psychobiotics

Although the majority of studies have been done on mice, there are a few human studies that have been conducted.  A small placebo-controlled study published in the journal Translational Psychiatry did show a positive effect using psychobiotics. In this study, the single strain probiotic Bifidobacterium longum 1714 was administered to a small group of subjects and mental health parameters were measured. 

The researchers exposed the subjects to a daily controlled stressor (socially evaluated cold pressor test [SECPT]) and then utilized many testing methods including EEG, neurocognitive assessments, cognitive tasks, and self-reporting to better understand how a controlled stressor affects stress levels and cognitive performance. The results showed the following:

  • Improved tolerance to stress
  • Subtle improvement over placebo in visuospatial memory performance
  • An EEG profile consistent with improved memory

In another placebo-controlled study published in the journal Bi-Polar Disorders, patients hospitalized for mania were either given a placebo or a probiotic combination of Lactobacillus rhamnosus strain GG and Bifidobacterium animalis lactis strain Bb12. After 24 weeks of taking the probiotic, there were 24 re-hospitalizations in the 33 placebo participants, and only eight re-hospitalizations in the 33 participants who received the probiotic. The researchers proposed that the probiotics helped modulate inflammation, which helped reduce relapse rates in those with mania. 

These two studies show us that supplementation with certain probiotic strains (psychobiotics) can have a positive effect on stress and depression.  This is great news in addition to the many mice studies that have shown positive mental health benefits with the use of psychobiotics.

More Research Is Needed

Although these human studies are groundbreaking, I will caution you that we do need more human studies to help us better understand how psychobiotics can affect mental health, and which psychobiotics will benefit particular mental health conditions. While there are many unanswered questions still, I am confident that over time more research will be done on psychobiotics and how they can improve mental health.

If you already regularly eat fermented foods, pre-biotic rich foods, and take probiotics, you are supporting a healthy gut microbiome, and there really is no need to make any changes. Stay tuned for more emerging studies on psychobiotics. This is a very exciting field of medicine that I think will only continue to grow. 



Dr. Drew Sinatra

Meet Dr. Drew Sinatra

Dr. Drew Sinatra is a board-certified naturopathic doctor and self-described “health detective” with a passion for promoting natural healing, wellness, and improving quality of life by addressing the root cause of illness in patients of all ages. His vibrant practice focuses on treating the whole person (mind, body, and spirit) and finding missed connections between symptoms and health issues that are often overlooked by conventional medicine.

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