Your Stomach Is Influencing Your Brain: 6 Surprising Facts About Microbes

"I'm so nervous, my stomach is all in a knot." Who among us has not said this at least once in our lives? Or, perhaps, you've had a "gut-wrenching experience." We know that our brains can stimulate reactions in other parts of our body. However, science is now revealing that this is not a simple one-way connection.

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A rich network of microbial life in our internal organs plays a powerful role in shaping critical metabolic functions and even influencing our moods and behavior. Contemporary research is uncovering previously unsuspected physiological pathways involving this crucial microbial life within us and changing our understanding of basic biology. It is even dramatically changing how we see ourselves as human beings. Fortunately, too, these new findings are provoking important research that will ultimately have a large impact on our heath.

Over the last several hundred years, successive waves of medical knowledge have substantially altered patient treatment. Antisepsis, anesthesia, antibiotics, and chemotherapy have profoundly affected the practice of medicine. Initially, many of these were minimally regarded or even vigorously resisted. This same pattern of dramatic progress and skepticism continues today just as in the past, and there are always new and startling discoveries. At this moment in our long medical journey, we have finally reached the era of the hologenome, and it represents an exceptionally far-reaching advance in our medical understanding of ourselves and our perception of our place among all nature's creatures.

The concept of the hologenome changes our basic understanding of complex organisms. When anyone looks into a mirror, they naturally see a single being. But, nature sees us very differently. Instead of that single organism we see in a mirror, we are in fact many incredibly complex networks of collaborative, cooperative, and competitive ecologies composed of our innate cells and almost incalculably numerous microbial inhabitants so effectively linked together that we feel that we are just one being. Within and on all of us is an entire microcosm of life so seamlessly a part of ourselves that we are not normally aware of it. We do not merely coexist with this additional life. They are essential to our wellbeing.
This new science of the hologenome is revealing a number of surprising facts:
1. The number of these microbial cells outnumber our own native cells by a factor of 10 to one. There are over 100 trillion of them in you and on you.

2. The amount of genetic material in those cells outnumbers our "own" genetic material by more than 100 to one. At least 10,000 species of microbes are part of you.

3. These microbes exist in microbial ecological communities, for example in the gut, and can have far-reaching effects, even on our brain and mood. Our intestines have more nervous tissue than our spinal cords, which is one reason that our gut can modulate brain activity.

4. The foods we eat can alter these microbial communities, affecting and even influencing complex human behaviors such as anxiety, learning, memory, satiety, and appetite. Preliminary research is indicating that the regular consumption of probiotic-rich foods, like some yogurts, may have beneficial effects on brain function by affecting our emotions, sensation, and thinking.

5. Our microbial partners have a crucial impact our immune systems and neurological functions. New therapies for neurological disorders are being evaluated including microbial treatments for multiple sclerosis and autism.

6. Our crucial metabolic functions are heavily dependent on our microbial inhabitants in ways that are just beginning to be explored. Obesity, diabetes, arthritis, autoimmune disorders, and even depression may one day be treated by adding specific microbes to our diets or by microbial transplants.

Furthermore, as our understanding of ourselves evolves, there must be a willingness to evaluate some existing medical interventions for possible unintended consequences. For example, antibiotics are commonly prescribed in children for respiratory infections. Yet, at this time, there is little understanding of how the normal gut flora of a child would be affected by those antibiotics and what the specific developmental, cognitive, and behavioral implications could be.

All of this new information represents exciting new avenues for research, unbiased evaluation, and testing. But for each of us, right now, there is a practical opportunity. As we learn about these associations, we can become attuned to our own unique body rhythms and demands. We can experiment with foods and try to carefully assess how they may alter how we feel. Try some probiotics and see if they change your mood or affect your sense of wellbeing or level of anxiety. And, go ahead, have a piece of chocolate if it makes you feel better. Your hologenome wants you to.

Dr. Bill Miller has been a physician in academic and private practice for over 30 years. He is the author of The Microcosm Within: Evolution and Extinction in the Hologenome. He currently serves as a scientific advisor to OmniBiome Therapeutics, a pioneering company in discovering and developing solutions to problems in human fertility and health through management of the human microbiome. For more information, head to

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