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Probiotics and Brain Health: So Happy Together

There seems to be no end to the exciting things we are learning about the microbiota, that collection of bacteria, viruses, fungi, and protozoa living on and inside our body. It has been said that the microbiota may weigh up to five pounds[1]—these are five pounds we do not want to lose, and for several reasons!

Experts have come to recognize an intimate connection between the microbiome (the environment where the flora lives), probiotics, and brain health. The bacteria living in the microbiome are busy, helping with digestion, protecting against bad bacteria that cause disease, producing vitamins, and regulating the immune system.

There is also the brain connection, or more specifically, the gut-brain axis.[2] (It has also sometimes referred to as the microbiota-gut-brain axis.[3]) There is constant communication between the brain, gut, and microbiota. The bidirectional exchange of information that occurs along the gut-brain axis involves chemical signals between the brain and the digestive system.[4] This close relationship between the primary brain and the “second brain”—the gut—means that our food choices, the condition of our digestive system, and the microbiota all have a significant impact on our brain health, emotions and mood,[5] cognitive function, reactions to stress, sleep, and our overall health.

Because the relationship between the brain and gut is so powerful, it only makes sense that you want—and need—to keep the gut in balance. Probiotics, or beneficial bacteria, can help with this critical task.

The Brain-Gut Axis and Brain Health

Aparna Lyer, MD, assistant professor of psychiatry at the University of Texas Southern Medical Center, said: “I can foresee more widespread usage of probiotics in the treatment of mental health, especially since most people can tolerate them well.”[6] This is promising news for everyone who wants to take better care of their brain health and the traffic that travels along the gut-brain highway.

This highway system is called the vagus nerve, which is the tenth cranial nerve that extends from the brainstem through the neck and thorax down to the abdomen. Signals move in both directions along this route, but guess which but guess which end of the axis sends the most messages? If you guessed the brain, you are wrong. Your gut actually does most of the “talking” to the brain, another indication that the gut and microbiota are necessary players in brain health.

You may be used to hearing about the central nervous system (brain and spinal cord) and the peripheral nervous system (PNS)—nerves that control muscles, organs, and sensations. However, there is a branch of the PNS in the gut known as the enteric nervous system that actually has more nerve cells than the spinal cord. This is one reason why the gut is referred to as the “second brain.”

Your second brain is where about 90 percent of your body’s supply of serotonin is produced before travelling to the brain. Serotonin is known as the “happy hormone,” because it plays an essential role in mood, happiness, and feelings of wellbeing. This hormone also enables brain and other nervous-system cells to communicate with each other; it also helps with digestion, eating, and sleeping. All these factors make it critical for you to keep your gut environment healthy so serotonin can continue to be produced and sent to the brain.

Probiotics and Brain Health

When there is an imbalance in the microbiota (a state known as dysbiosis) caused by too many unhealthy species of bacteria or other microbes, the brain can be affected. For example, dysbiosis has been associated with an increase in depressive symptoms.[7] Research findings demonstrate the link between the state of the microbiota and the brain.

Enter probiotics, the live bacteria and yeasts available in selected foods and supplements that have been shown to be beneficial for a variety of health conditions. The most common types of bacteria classified as probiotics belong to one of two groups: Lactobacilli or Bifidobacteria. Mostly, you may be familiar with their use to help with digestion, diarrhea, irritable bowel syndrome, allergies, and inflammatory bowel disease. Probiotics also may boost immune-system function and help promote heart health.

However, more and more researchers and health professionals are examining the probiotics’ ability to help with mental health and brain health. Some species, for example, have demonstrated an ability to help with mood and anxiety disorders in clinical trials.[8]

Psychoprobiotics and Brain Health

That brings us to a growing interest in “psychobiotics,” beneficial bacteria which have been shown to help balance your mood and behaviour as well as improve depression and anxiety symptoms, when taken in adequate amounts. Two probiotics, in particular, have demonstrated good results against depression and anxiety: Bifidobacterium longum and Lactobacillis helveticus. These bacteria amplify serotonin. Anxiety and depression are often linked with inflammation; probiotics have an ability to reduce inflammation through the immune system.

In a study, the two probiotics were given for two weeks to a group of rats and, for 30 days, to a group of healthy human volunteers. The use of the probiotics was shown to significantly reduce anxiety-like behaviour in the animals and to reduce psychological distress in the human volunteers.[9]

Choosing Probiotics

Which probiotics should you buy? Always look for a multistrain supplement that provides at least 10 to 20 billion colony-forming units (CFUs). This number refers to how many viable bacterial cells in a sample can divide and form colonies. Your individual dosing needs should be discussed with a knowledgeable health-care provider.

Look for enteric-coated and refrigerated probiotics. The coating protects the live bacteria from the harsh gastric acid and allows them to reach the intestinal tract where they can get to work and benefit your intestinal flora.

Andrea Donsky, RHN

Andrea Donsky is a Registered Holistic Nutritionist and founder of—a multiple award-winning website. She has 21 years of experience in the health and wellness space, and is a multiple award-winning influencer.


  1. Hair, M., and J. Sharpe. “Fast facts about the human microbiome.” Center for Ecogenetics & Environmental Health, January 2014,
  2. Carter, K. “Gut-brain axis: The connection between brain health and your gut.”,
  3. Capuco, C., I. Urits, J. Hasoon, R. Chun, B. Gerald, J.K. Wang, H. Kassem, et al. “Current perspectives on gut microbiome dysbiosis and depression.” Advances in Therapy, Vol. 37, No.4 (2020): 1328–1346.
  4. Mitchell, D. “The latest research on gut-brain health.”,
  5. Mitchell, D. “How your microbiome affects mood and mental health.”,
  6. Chesak, J. “The no BS guide to probiotics for your brain, mood, and gut.” Women’s Wellness, updated 2020-⁠03-⁠29 (reviewed by D.R. Wilson 2017-⁠08-⁠25),
  7. Capuco  C., I. Urits, J. Hasoon, R. Chun, B. Gerald, J.K. Wang, H. Kassem, A.L. Ngo, A. Abd-⁠Elsayed, T. Simopoulos, A.D. Kaye, and O. Viswanath. “Current perspectives.”
  8. Slyepchenko, A., A.F. Carvalho, D.S. Cha, S. Kasper, and R.S. McIntyre. “Gut emotions—Mechanisms of action of probiotics as novel therapeutic targets for depression and anxiety disorders.” CNS & Neurological Disorders Drug Targets, Vol. 13, No.10 (2014): 1770–1786.
  9. Messaoudi, M., R. Lalonde, N. Violle, H. Javelot, D. Desor, A. Nejdi, J.-⁠F. Bisson, et al. “Assessment of psychotropic-like properties of a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in rats and human subjects.” The British Journal of Nutrition, Vol. 105, No.5 (2011): 755–764.

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