All diseases begin in the Gut! – Hippocrates, 460 – 370 BC

The gut-brain axis (GBA) consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions. ¹ Due to this connection via the vagus nerve, gut microbiota can greatly influence our cognitive functions, such as learning, memory and decision making processes, as well as emotions and behavioural patterns. ²

An intact gut lining and its microbes protect the host from pathogens, metabolizing complex lipids and polysaccharides that otherwise would be inaccessible nutrients, neutralizing drugs and carcinogens, modulating intestinal motility, and making visceral perception possible. However, chronic exposure to pathogenic bacteria, toxins, stress, high blood sugar and gut-irritating food substance can lead to a compromised gut lining, which is commonly referred to as leaky gut.

So how is Leaky Gut related to Leaky Brain?

It is a passage by Dr. David Perlmutter, MD, FACN, ABHIM on the topic³:

You may have heard about the perils of a leaky gut, where the protective junctions in the intestinal lining become compromised. This is a response to a variety of factors, including pathogenic bacteria, some medications, stress, environmental toxins, elevated blood sugar, and potentially gut-irritating food ingredients like gluten.

Once the intestinal barrier is compromised, undigested food particles leak into the bloodstream, where they elicit an immune response. This can create systemwide inflammation.

When your intestinal barrier is compromised, you become susceptible — due to that increased inflammation — to a spectrum of health challenges, including arthritis, eczema, allergies, and even autism, Alzheimer’s, and Parkinson’s. (For more on leaky gut syndrome, see “How to Heal a Leaky Gut“.)

Still, the problems of a leaky gut become even more monumental in light of new science that shows how loss of gut integrity can lead to a “leaky” brain.

We’ve long assumed that somehow the brain was insulated from what goes on in the rest of the body. You’ve heard about the highly protective, fortified portal keeping bad things out of the brain — the blood-brain barrier. We used to think of this barrier as an impenetrable wall.

The problems of a leaky gut become even more monumental in light of new science that shows how loss of gut integrity can lead to a “leaky” brain.

It has now become clear that many substances threaten its integrity. And once the brain’s barrier is compromised, various molecules that may spell trouble — including proteins, viruses, and bacteria — can get inside it.

For an example of how dangerous this can be, look at how the lipopolysaccharide (LPS) molecule behaves once it gets outside the gut.

LPS makes up the protective outer membrane of a class of bacteria that typically represents 50 to 70 percent of our intestinal flora. We’ve long known that LPS induces a violent inflammatoryresponse in animals if it finds its way into the bloodstream. It’s so violent that it’s also termed an endotoxin, a toxin that comes from within the bacterial cell.

In one critically important study on LPS, researchers at Texas Christian University showed that injections of LPS into lab animals’ bodies (not brains) led to overwhelming learning deficits, demonstrating that LPS was able to cross the blood-brain barrier.

In addition, the animals developed elevated levels of the protein beta-amyloid in their hippocampi, the brain’s memory center. (Beta-amyloid is strongly implicated in Alzheimer’s.)

Other studies have implicated LPS in memory problems and decreased production of BDNF (brain-derived neurotrophic factor), a protein that is critical for the growth of new brain cells.

This is powerful information that once again speaks to the gut-brain connection and the impact of inflammation, gut permeability, and the critical importance of a healthy gut to a healthy brain.

Dr. David Perlmutter, MD, FACN, ABHIM is a board certified neurologist and fellow of the American College of Nutrition, and an associate professor at the University of Miami’s Miller School of Medicine. He is the author of the No. 1 New York Times bestseller Grain Brain and Brain Maker: The Power to Heal and Protect Your Brain — for Life, from which this article is adapted.


  1. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems
  2. The microbiota–gut–brain axis: neurobehavioral correlates, health and sociality
  3. Healthy Gut, Healthy Brain
  4. Image from: Role of Gut-Brain Axis in the Aetiology of Neurodevelopmental Disorders with Reference to Autism

“He who has health, has hope; and he who
has hope, has everything.”

Thomas Carlye