Lillian Wilson

The Second Brain by Michael D. Gershon

The Second Brain is a comprehensive exploration of the gut's enteric nervous system and its profound role in our health and well-being.

The Second Brain

The book has received 3.74 ⭐️ on GoodReads.

Gastric issues and the captivating domain of gut health have long piqued both medical experts and inquisitive minds. Often hailed as our second brain, the gut’s role goes well beyond digestion, extending into the realms of mental health and overall well-being. As gastrointestinal ailments and functional bowel disorders affect a growing number of individuals, understanding the complexities of this essential system becomes paramount.

In this review, we delve into The Second Brain by Dr. Michael D. Gershon, an eminent figure in gastrointestinal research. This book takes us on a journey through the enigmatic enteric nervous system, a frequently overlooked yet vital component of our health.

Author’s background

Dr. Michael D. Gershon, MD, holds the position of Chairman at the Department of Anatomy and Cell Biology within Columbia University’s College of Physicians and Surgeons at the Columbia-Presbyterian Medical Center in New York City.

Dr. Michael D. Gershon (r)

Throughout his three decades of dedicated research, Dr. Gershon has focused on comprehending the workings of the human gastrointestinal system, encompassing the stomach, oesophagus, small intestine, and colon. His extensive investigations have led to an astounding revelation: the existence of neural cells within the gut that function as a quasi-brain.

What is the book about?

The Second Brain by Michael D. Gershon is a captivating exploration of the enteric nervous system, often referred to as the “second brain.” In this book, Gershon dives into the previously overlooked and mysterious realm of the gut’s intrinsic nervous system, unveiling its inner workings and its crucial role in our overall health and well-being. Organised into three distinct parts, the book covers the following key subjects:

1. Unveiling the notion of a second brain residing in the gut.

2. Illuminating the structure and functionality of the nervous system.

3. Investigating the intricate processes of digestion and nutrient absorption.

4. Identifying potential threats that can arise within the digestive system.

5. Examining the collaborative efforts between the second brain and the immune system to defend against microbial intruders.

6. Emphasising the potential advantages that a deeper comprehension of the second brain holds for millions of individuals, particularly the 40% of adults grappling with functional bowel disorders.

Table of contents

  • Preface
  • Part I: The Early Breakthroughs
  • Chapter 1: The Discovery of the Second Brain
  • Chapter 2: The Autonomic Nervous System and the Story of Chemical Neurotransmission
  • Chapter 3: The Turning Point
  • Chapter 4: The Workshop
  • Part II: The Travelogue
  • Chapter 5: Beyond the Teeth: The Domain Stalked by Heartburn and Ulcer
  • Chapter 6: Onward and Downward
  • Chapter 7: “It Ain’t Over ‘Til It’s Over’
  • Chapter 8: A Bad Bowel
  • Part III: The Origin of the Second Brain and Its Disorders
  • Chapter 9: The Enteric Nervous System Now
  • Chapter 10: Immigrants and the Lower East Colon
  • Chapter 11: Location, Location, Location
  • Chapter 12: The State of the Bowel
  • Acknowledgments
  • Endnote: Animals in Biomedical Research
  • Index
  • Copyright
  • About the Publisher

Three key takeaways from The Second Brain

1Gut as the second brain

Michael D. Gershon presents a profound exploration of the gut as the second brain. Gershon delves into the history of this rediscovery, highlighting the work of pioneers like Bayliss and Starling, who established the existence of the enteric nervous system in the gut. This intrinsic nervous system, often overlooked in other organs, exhibits remarkable properties, including the ability to initiate reflexes independently.

Through experiments like Trendelenburg’s, it became evident that the gut’s intrinsic nervous system possesses brain-like capabilities. This revelation reshapes our understanding of the gut’s significance and its intricate neural network, shedding light on the remarkable second brain that plays a pivotal role in our bodily functions.

2Nervous-digestive systems connection

The digestive system’s top and bottom ends, controlled by the brain, play a crucial role in determining bowel function, and this connection between the brain and gut can be influenced by mental conditions. Various psychiatric illnesses, like eating disorders and personality disorders, can manifest with enteric symptoms, highlighting the strong connection between mental health and gastrointestinal function.

While it’s commonly believed that thoughts can affect gut behaviour, it’s essential to recognise that enteric illness can originate independently within the enteric nervous system, not solely due to mental influence.

Understanding the intricacies of the enteric nervous system and its role in gastrointestinal health is essential, especially in addressing conditions like functional bowel disease, where symptoms can be debilitating yet often lack a clear pathological link. While previous limitations in studying the enteric nervous system have impeded progress, recent advancements in the field provide hope for identifying specific diseases and developing effective therapies, potentially improving the lives of those affected by functional bowel diseases.

3The role of the colon in the development of the nervous system

Delves into the fascinating evolutionary and physiological aspects of the colon. It highlights how the colon likely evolved as a mechanism to help land animals conserve water through the process of salt removal, ultimately aiding in water absorption.

The book discusses the presence of symbiotic bacteria in the colon and the role of diarrhoea in cleansing the colon of pathogenic bacteria. Additionally, it explores groundbreaking research on congenital megacolon, revealing insights into the formation of the enteric nervous system in mice and the importance of neural crest-derived cells. This book provides a comprehensive understanding of the colon’s function, evolution, and its vital role in the development of the enteric nervous system.

Strengths and weaknesses, according to readers’ reviews


  • The book excels in providing in-depth and well-written biological explanations, covering structural, neurological, and biochemical aspects of gut function, making it a valuable resource for those seeking detailed scientific knowledge.

  • The author skillfully injects intellectual humour throughout the book, adding an engaging and lighthearted touch to the dense biological content.

  • For readers interested in delving deep into the subject, the book offers a wealth of information, including extensive coverage of chemical names for enzymes and neurotransmitters in the gut.


  • The abundance of biological terminology and dense scientific substance may make the book less accessible to a broader audience, potentially alienating readers seeking a more approachable and user-friendly exploration of the topic.

  • The book focuses heavily on scientific theory and research but may leave readers wanting more real-world applications or insights into how the knowledge presented can be practically applied to address gastrointestinal disease or mental health concerns.

Best quotes from The Second Brain

“Surveys have shown that over 40 percent of patients who visit internists do so for gastrointestinal problems. Half of those have “functional” complaints.”
“On the other hand, unlike the skin, the intestinal lining has also to participate in the critical processes of digestion and absorption. Digestion is the term for the variety of means by which the complex and often very large molecules in food are converted to simpler and smaller molecules that can then be moved from the lumen of the gut into the body. Absorption is the term for the transport of the products of digestion across the lining of the bowel to reach blood and lymph vessels in the wall of the intestine.”
“When I learned that over 95 percent of the body’s serotonin is made in the bowel, therefore, I decided that the organ had promise. In fact, I now know that my original concept of a “simple” nervous system was wrong. A simple nervous system is an oxymoron, like jumbo shrimp; nevertheless, the enteric nervous system, the nervous system of the gut, is simpler than the brain, and its study has served to keep me off the streets.”

Final takeaway

The Second Brain by Dr. Michael D. Gershon offers a captivating exploration of the enteric nervous system, shedding light on the remarkable second brain residing in our gut. While the book excels in providing comprehensive biological explanations and injects intellectual humour into its content, it may be too densely packed with scientific terminology for a general readership. However, it serves as an invaluable resource for those seeking an in-depth understanding of the gut’s intricate neural network. Readers with a strong interest in gastrointestinal science and neurobiology will find this book a valuable addition to their library, offering profound insights into the fascinating world of the gut’s second brain.

Where to buy

You may purchase The Second Brain on Amazon at the best price. It is available in paperback, audio and Kindle versions, so you may choose an option that appeals to you the most.

Healthypedia FAQ

It is a detailed book best suited for those with a strong interest in the subject, not for practical, quick insights.

Yes, the book is reliable, authored by Dr. Gershon, a respected gastrointestinal researcher, and well-referenced.

No, it is quite technical; newcomers may find it challenging. Start with more accessible resources for an introduction to the topic.

Link is copied