Is 'Leaky Gut' the Root of All Ills?

John Watson


May 23, 2019

In This Article

Everyone loves a simple answer to a complex problem, so it's probably not surprising that "leaky gut syndrome" is such a popular catchall diagnosis, at least on the Internet. As the theory goes, the intestinal mucosal barrier becomes increasingly permeable, allowing harmful toxins and bacteria to enter the bloodstream and cause havoc throughout the body. Many blame this digestive disorder for everything from depression and eczema to fibromyalgia and more.

The trouble is that "leaky gut syndrome" is not recognized by the established medical community, and it's not listed among the thousands of diagnoses in the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10). However, it's related to just enough actual evidence to make it intriguing.

Although researchers have begun to outline the potential role of increased intestinal permeability in several disorders, primarily gastrointestinal conditions, their findings are more nuanced than anything you'll find on the Internet about "leaky gut syndrome."

Dynamic and Highly Regulated

Alessio Fasano, MD

One of the key reasons we're hearing so much about the intestinal barrier is because, relatively speaking, we're just beginning to understand how it functions, said Alessio Fasano, MD, W. Allan Walker chair of pediatric gastroenterology and nutrition at Massachusetts General Hospital in Boston.

"Until recently, we were under the impression that the gut barrier is made of single layers of cells that were thought to be almost cemented to each other," Fasano said. "This vision changed in the early 1970s when a Japanese research group[1] demonstrated for the first time that the spacing between cells is not static but dynamic, and it can be modulated by the presence of structures called 'tight junctions.'"

Gail Hecht, MD

"These tight junctions are structured to allow for a natural give-and-take within the intestine," said Gail Hecht, MD, MS, AGAF, chair and scientific advisory board member for the American Gastroenterological Association Center for Gut Microbiome Research & Education, and chief of gastroenterology and nutrition at Loyola University Chicago. She has been studying this aspect of human physiology for more than three decades.

"Tight junctions are very highly regulated to let things in and keep other things out," added Hecht. "This keeps the intestine from acting like a sieve where all kinds of things can just pass through."

The tight junctions maintain the balanced permeability that our health depends upon, keeping harmful antigens and microorganisms from affecting our immune system while simultaneously allowing the passage of water, nutrients, and ions required for our survival.[2,3,4]

However, certain circumstances can cause these tight junctions to allow greater outflow, which is sometimes referred to as "leaky gut" even in the academic literature. Hecht and other experts believe this term can be misleading, implying that something is malfunctioning in the body; usually, increased permeability is a natural response that causes no adverse effects.

Jerrold Turner, MD, PhD

In fact, our immune systems are conditioned to deal with intestinal permeability outside the range of what is deemed normal, according to Jerrold Turner, MD, PhD, professor of pathology and medicine at Harvard Medical School in Cambridge, Massachusetts. It only seems to be problematic when increased intestinal permeability accompanies other underlying conditions.

"Disease is a vicious cycle," Turner said. "In someone who already has a mucosal immune regulatory defect that causes an immune disease, throwing in increased intestinal permeability might just be enough to ignite the fire again."


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