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Leaky gut syndrome, or intestinal hyperpermeability, has gained much more attention in the past two decades—despite some debate about whether or not it is an actual condition.
Leaky gut syndrome is thought to cause digestive symptoms, trigger inflammation, and contribute to a wide variety of health issues, ranging from acne and arthritis to migraines and metabolic syndrome.
But what is leaky gut, exactly? And what causes it? In this article, we’ll answer these questions and more, including ways to treat it with supplements and nutrition.
The more scientific term for leaky gut is “increased intestinal permeability” or “intestinal hyperpermeability,” meaning that a part of the small and large intestines becomes excessively permeable.
Leaky gut is thought to occur when the one-cell-thick layer of epithelial cells lining the intestines becomes “leaky” with growing gaps between the cells.
When this happens, the excessive permeability may allow toxins, pathogens, or proteins to travel out of the digestive tract into the bloodstream. This is thought to contribute to a myriad of health issues, although the research isn’t always conclusive.
Here’s what we do know: our intestinal barrier lining is only one cell thick, made up of epithelial cells that are constantly renewing themselves. We need a strong and tight intestinal barrier to control what enters the bloodstream and what stays inside the gut.
Epithelial cells in the intestinal lining are “sealed” together by protein complexes called tight junctions, which act like a physical barrier between the gut and the bloodstream.
Essentially, tight junctions are gatekeepers between the bloodstream and gut, allowing water and nutrients to pass through but keeping out toxins, most proteins, and pathogens from entering. If the gaps between tight junctions start to become too big, the stuff we want to keep in our guts (typically to be eliminated) can escape (i.e., “leak”) into the rest of the body.
When too-big proteins and toxins enter the bloodstream, the body’s immune response is activated to deal with the invader. This elevates inflammation and is thought to contribute to chronic diseases related to inflammation (which are just about all of them).
The gut lining also uses another barrier to keep things out, which is made up of mucus, immune cells, antimicrobial peptides, and a gel-like coating of proteins called the glycocalyx. These molecules create a sticky surface that physically traps harmful pathogens or chemically prevents them from adhering to epithelial cells. In addition to increasing gaps between tight junctions causing leaky gut, dysfunction in this mucosal barrier is also implicated in intestinal permeability.
But what causes these mechanisms to break down in the first place? Let’s take a look.
Although the term “leaky gut” has been found in the scientific literature as far back as the 1970s, researchers are still trying to figure out exactly what causes it. Like many gut-related conditions, there are many potential causes of leaky gut.
In 2000, Dr. Alessio Fasano and his team discovered a protein called zonulin that regulates the permeability of the intestines.1
Elevated zonulin levels cause the tight junctions between intestinal epithelial cells to open up too much, creating the characteristic gaps of leaky gut. Two conditions that cause zonulin activation are dysbiosis—excessive harmful bacteria in the gut microbiome and too few healthy ones—and gluten consumption in sensitive people.
Some other contributing factors that contribute to leaky gut include:
The most apparent symptoms of leaky gut are digestive-related, including bloating, gas, cramping, abdominal pain, constipation, or diarrhea.
There are also potential non-digestive symptoms or conditions associated with leaky gut, including:
However, it can be difficult to determine if leaky gut causes these conditions or is a symptom of them. Some research with animals has found that increased intestinal permeability occurs before the onset of some diseases, including type 1 diabetes, celiac disease, and IBS, suggesting that leaky gut can, in fact, be the cause rather than the symptom in some cases.7,8
There is no single gold standard for treating leaky gut, but targeting its root cause is a first step. A functional medicine practitioner can help you figure out what is causing your elevated intestinal permeability.
Some ways to treat leaky gut may include correcting gut dysbiosis, reducing inflammation, improving diet, treating digestive conditions, managing body weight, or reducing stress.
Prebiotics are types of dietary fiber that provide fuel for intestinal cells in the form of short-chain fatty acids. They also benefit the leaky gut by strengthening the gut barrier, increasing the growth of healthy bacteria, and supporting healthy immune cell functioning.
Prebiotics can come in supplemental or food forms, such as garlic, onions, leeks, asparagus, and chicory. One study found that people who increased their daily fiber intake from 19 grams to 29 grams had significantly reduced zonulin levels over the six-month study. Zonulin tests are one of the main ways to test for intestinal permeability.9
It’s thought that soluble fiber especially helps leaky gut because the intestinal fermentation of soluble fiber boosts butyrate production, which strengthens intestinal barrier function.
As gut dysbiosis is involved in the development of intestinal permeability, probiotics may help balance the gut microbiota.
One study with animals found that probiotic strains benefited leaky gut in mice, including reducing gut dysbiosis, inflammation, and metabolic dysfunction. The probiotic bacteria also increased tight junctions between epithelial cells.10
Probiotic supplements have also been shown to be beneficial for other digestive disorders, including inflammatory bowel disease (like Crohn’s disease and ulcerative colitis), irritable bowel syndrome, and celiac disease, which could help prevent or improve leaky gut by reducing those gastrointestinal symptoms.
In addition to probiotic pills, increasing dietary probiotics can boost the diversity of beneficial bacteria in the gut microbiome. Dietary probiotics are found in fermented foods, including sauerkraut, kimchi, yogurt, natural pickles, miso, natto, tempeh, kombucha, and kefir.
A few other supplementary that may help with different aspects of leaky gut include:
Although a gluten-free diet is not needed for everybody, it’s thought to improve leaky gut in people with high genetic susceptibility. Gluten can trigger zonulin activation in some people, which is known to increase the gaps between tight junctions and contribute to leaky gut.
One older study found that 87% of people with celiac disease (who absolutely need to be on a gluten-free diet) had normalization of their increased intestinal permeability after one year of eating gluten-free. Conversely, people who consumed even trace amounts of gluten had increased markers of leaky gut at the next visit.11
If you suspect you have leaky gut and want to heal it through diet, consider consuming foods high in antioxidants, anti-inflammatory foods, and nutrient-dense foods.
Some foods that can help with leaky gut (such as those high in polyphenols) include:
Limiting or avoiding foods, drinks, and medications that trigger inflammation is also needed to prevent or treat leaky gut.
Pro-inflammatory foods, beverages, or medications that may cause dysbiosis and damage the intestinal lining include:
There are many potential triggers for leaky gut, with some of the most common being a poor diet high in sugar and unhealthy fat, excessive alcohol consumption, gut dysbiosis (which often comes from an unhealthy diet), and consumption of gluten in sensitive people. These factors can all cause increased intestinal permeability.
Not necessarily, although it can vary individually. Coffee is full of antioxidants, but some people don’t tolerate it well. Plus, what you add to your coffee is also important—if you add loads of flavorings and sugar, then, yes, your favorite coffee may be bad for leaky gut.
The main tests for leaky gut are zonulin levels, which are elevated in cases of intestinal hyperpermeability, and the lactulose-mannitol test, which measures the absorption of two different sugars (lactulose and mannitol) through the gut. If high levels of both sugars are found in the urine after drinking the lactulose-mannitol solution, it may indicate increased intestinal permeability. However, tests for leaky gut are not standardized because many doctors do not recognize leaky gut syndrome as a medical diagnosis.
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