test-Understanding The Gut-Brain Connection
Digestive Health
Understanding The Gut-Brain Connection
Medically reviewed by Stephen Langer, MD • May 31, 2024

Understanding the Gut-Brain Connection

Maintaining a healthy gastrointestinal (GI) tract is an important part of overall wellness, as that system is responsible for digesting and extracting nutrients from the food we eat. It’s also the location of around 70% of our body’s immune cells,1 so better GI health can mean better immune health. Dr. Stephen Langer points out the direct importance and effect of thriving gastrointestinal environment by comparing its relative influence on overall wellness: “the weight of the microbiome in our digestive system…weighs more than our own brain!” and beyond volume alone, contains millions more genomes than that of the brain, rivaling its impact on wellness throughout the body.

Wellness, however, means more than simply making sure our bodies are healthy. It also involves caring for our cognitive and mental wellbeing. Enjoying a healthy mood and supporting functions like focus and memory are very important to our everyday experience and our ability to take care of ourselves and others.

What the scientific body of research is increasingly discovering is that mental wellbeing is connected in ways which may not have seemed obvious to past generations. But that is changing, as Dr. Langer contends that while the health food industry has always valued probiotics and gut health, the biotech industry has only recently begun to gain interest. He says that these days, “the microbiome…is one of the hottest areas of biotechnology research. They’re racing to develop new products for the microbiome.”

The connection between your gut health and mental and cognitive health is being examined in new and exciting ways, providing a new framework for the “gut-brain connection.” Let’s look closer at this axis of wellbeing and see how exactly we can play an active role in ensuring that our overall health, from gut to brain, is in peak condition.

What is the gut-brain connection?

When we speak of the connection between the gut microbiota (the microorganisms that live in a particular environment) and the brain, what we’re really discussing is the bidirectional communication which exists between the enteric (located in the GI tract) nervous system and the central nervous system.2 For the sake of clarity, the enteric nervous system is a peripheral system that permeates the GI tract and traces its routes through the bowels.3 This system governs such processes as the movement of food through the intestines, and the functions of nutritional absorption and immune activity.3 It may work in conjunction with or independent of the central nervous system. The central nervous system is the brain and spinal cord, with the brain functioning as the center of cognitive and emotional activity and the spinal cord providing the pathways for the transfer of information to and from the brain.4

When the two systems work in harmony with clear bidirectional communication, we call this the gut-brain connection.

This fascinating interaction is described by Dr. Langer as “one of the hottest areas of research,” because, he notes, a number of neurological and even psychological conditions are associated with changes in the microbiome. He explains that “the bacteria in the microbiome put out messenger molecules [“metabolites”] which enter the blood and can pass through the blood-brain barrier. In fact, the microbiome puts out molecules and hormones which affect neuropod cells in the lining of the gut which in turn put out synapses to the vagus nerve.” The vagus nerve controls several unconscious bodily functions, like digestion or breathing; neuropod cells are those which transform sensory information into neurons that can then deliver information to the brain.5

Therefore, understating the gut-brain connection, and its role in the interactions of the central and enteric nervous systems, may hold the key to unlocking exciting new benefits for overall health and wellness. Those benefits could range from improved heart health to a more positive mood.

How to improve the gut-brain connection

Recent research seems to indicate a direct link in the communication between the central and enteric nervous systems and the microbiota present within the gut.2 The microbiota include tiny organisms such as bacteria. Some of these bacteria offer a beneficial effect to our digestive health and are referred to as probiotics. For more detailed information on the types of microorganisms present within the GI tract, read Prebiotics vs. Probiotics vs Postbiotics.

Scientists are learning more about how the microbiota in the GI tract, including probiotics, play a pivotal role in the bidirectional communication between the nervous systems involved. This role, one among many, seems to be that of a go-between, delivering important information via messenger cells which then initiate gut functions, but which also have an impact on higher cognitive function.2

In fact, in clinical studies, the role of probiotics in interacting with both the central nervous system and the enteric nervous system is becoming clearer, particularly with regard to metabolic and neuroendocrine pathways, the routes by which messages are delivered between the endocrine system and the brain.2 In humans, this interaction has even been indicated as influencing such higher cognitive functions as mood and other aspects which may be examined and diagnosed by medical professionals.2

Simply put, if you want to support the gut-brain connection in your own body, you will want to consider your overall digestive health, especially relating to the gut microbiota and probiotics.

Probiotics and mental health

Dr. Langer states that the gut microbiota release “molecules and hormones that affect different parts of the brain that affect the emotions.” Scientific research into the link between probiotics and mental health is on-going, with new observations being made as clinical tests seek to better understand the method and effects of communication between the gut microbiota and the brain. Some research has indicated that a central mechanism in this communication is linked to the short-chain fatty acids (SCFA) produced in the colon by microorganisms.6 These SCFAs are considered metabolites (enzymatic by-products) created by the microbiota and are understood to possess neuroactive (causing a change in the brain) properties which can have an effect on the brain through the bidirectional communication known as the gut-brain connection. Although definitive and conclusive evidence is still being gathered by researchers, it is beginning to appear as though these metabolites play a direct role in the functioning of the brain, particularly in relation to mental wellbeing.6 Such indications are inspiring further research and even efforts to develop treatments for certain conditions based on the metabolite influence of the gut microbiota on the central nervous system and the brain.

Healthy probiotic balance within the gut is also seen as crucial in the proper development of both the central and enteric nervous systems.2 Even more interesting is the observation that healthy responses to stress and a decrease in behaviors associated with anxiety7 may be dependent on healthy colonies of probiotics in the subjects’ GI tracts.8 The balance that these probiotics provide can benefit both mental health and overall GI wellness.2

Probiotic supplements for a healthier gut-brain connection

While previous generations may have eaten diets which contributed more to their digestive health, it can be challenging today to make sure you’re supporting a healthy GI balance and thriving probiotic environment. As Dr. Langer says, “most people’s diets are suboptimal,” which is a problem as he explains that the diet is the largest factor in determining the health of the microbiome. For that reason, it’s important to make sure you’re getting plenty of fruits and vegetables in your daily diet for natural sources of fiber, vitamins and polyphenols. It’s also a good idea to consider adding a science-backed probiotic supplement to your daily health regimen.

One such option is Dr. Langer’s own Ultimate 16 Strain Probiotic with FOS. This formula is comprised of 16 highly beneficial strains of probiotics, including those experimentally proven to offer potent benefits and to help support vibrant digestive and immune health while also promoting a strong gut-brain connection. It also includes FOS (fructooligosaccharides), a type of prebiotic sugar which Dr. Langer says reaches the large intestine to nourish the microbiome and promote the proliferation of probiotics in the gut. He concludes that, “it would behoove those who don’t get sufficient fiber and natural polyphenols from their diet to nourish the microbiome.”


Our bodies are incredibly complex and operate at their best when each system is able to function in balance and harmony. By promoting the health of the GI tract and the microorganisms within it, we’re also able to support other areas of wellness, such as mental and cognitive health. Supplementing with probiotics is a great way to support this goal and can contribute to a healthier gut-brain connection.

You be well, now.


Dr. Stephen Langer

About Dr. Stephen Langer

Dr. Langer has practiced Wellness Medicine and Clinical Nutrition for his entire medical career. He is the author of numerous books including the bestsellers “Solved the Riddle of Illness” and “Solved: the Riddle of Weight Loss”. Dr. Langer has produced and hosted two nationally syndicated television series and was the medical editor of a nationally distributed newspaper. Dr. Langer is proud to have had a strong, successful professional relationship with Swanson Health Products for over 40 years.

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.


  1. The Interplay Between the Gut Microbiome and the Immune System. Nutrients. Read source
  2. The Gut-Brain Axis. Annals of Gastroenteroly. Read source
  3. The Enteric Nervous System. Gastroenterology. Read source
  4. Central Nervous System. National Library of Medicine. Read source
  5. Neuropod Cells. National Library of Medicine. Read source
  6. The Role of Short-Chain Fatty Acids. Frontiers in Endocrinology. Read source
  7. Reduced Anxiety-Like Behavior. Neurogastroenterology and Motility. Read source
  8. Normal Gut Microbiota Modulates Brain Development and Behavior. Proceedings of the National Academy of Sciences of the USA. Read source