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Is Leaky Gut Syndrome a Real Condition? An Unbiased Look

A phenomenon called “leaky gut” has gained quite a bit of
attention lately, particularly among natural health
enthusiasts.

Leaky gut, also known as increased intestinal permeability, is
a digestive condition in which bacteria and toxins are able to
“leak” through the intestinal wall.

Mainstream medical professionals do not recognize leaky gut as
a real condition.

However, there is quite a bit of scientific evidence that leaky
gut does exist and may be associated with multiple health
problems.

This article takes a critical look at the evidence on leaky gut
syndrome.

Woman Holding a Model of Human Intestines

What Is Leaky Gut?

The human digestive tract is where food is broken down and
nutrients are absorbed.

The digestive system also plays an important role in protecting
your body from harmful substances. The walls of the intestines
act as barriers, controlling what enters the bloodstream to be
transported to your organs.

Small gaps in the intestinal wall called tight junctions allow water and nutrients to pass
through, while blocking the passage of harmful substances.
Intestinal permeability refers to how easily substances pass
through the intestinal wall.

When the tight junctions of intestinal walls become loose, the
gut becomes more permeable, which may allow bacteria and toxins
to pass from the gut into the bloodstream. This phenomenon is
commonly referred to as “leaky gut.”

When the gut is “leaky” and bacteria and toxins enter the
bloodstream, it can cause widespread inflammation and possibly
trigger a reaction from the immune system.

Supposed symptoms of leaky gut syndrome include bloating, food
sensitivities, fatigue, digestive issues and skin problems
(1).

However, leaky gut is not a recognized medical diagnosis. In
fact, some medical professionals deny that it even exists.

Proponents claim that it’s the underlying cause of all sorts of
conditions, including chronic fatigue syndrome, migraines,
multiple sclerosis, fibromyalgia, food sensitivities, thyroid
abnormalities, mood swings, skin conditions and autism.

The problem is that very few scientific studies mention leaky
gut syndrome.

Nevertheless, medical professionals do agree that increased
intestinal permeability, or intestinal hyperpermeability,
exists in certain chronic diseases (1, 2).

Summary: Leaky gut, or intestinal
hyperpermeability, is a phenomenon that occurs when the tight
junctions of the intestinal wall become loose, allowing
harmful substances to enter the bloodstream.

What Causes Leaky Gut?

Pile of Glazed Donuts

Leaky gut syndrome remains a bit of a medical mystery, and
medical professionals are still trying to determine exactly
what causes it.

A protein called zonulin is the only known regulator of intestinal
permeability (3, 4).

When it’s activated in genetically susceptible people, it can
lead to leaky gut. Two factors that trigger the release of
zonulin are bacteria in the intestines and gluten, which is a
protein found in wheat and other grains (3, 4, 5).

However, some studies have shown that gluten only increases
intestinal permeability
in people with conditions like
celiac disease or irritable bowel syndrome (6, 7).

There are likely multiple contributing factors to leaky gut
syndrome.

Below are a few factors that are believed to play a role:

  • Excessive sugar intake: An unhealthy diet
    high in sugar, particularly fructose, harms the barrier
    function of the intestinal wall (8, 9).
  • Non-steroidal anti-inflammatory drugs
    (NSAIDs):
    The long-term use of NSAIDs like ibuprofen
    can increase intestinal permeability and contribute to leaky
    gut (10, 11, 12).
  • Excessive alcohol intake: Excessive alcohol
    intake may increase intestinal permeability (10, 13).
  • Nutrient deficiencies: Deficiencies in
    vitamin A, vitamin D and zinc have each been implicated in
    increased intestinal permeability (8, 14, 15).
  • Inflammation: Chronic inflammation
    throughout the body can contribute to leaky gut syndrome
    (16).
  • Stress: Chronic stress is a contributing
    factor to multiple gastrointestinal disorders, including
    leaky gut (17).
  • Poor gut health: There are millions of
    bacteria in the gut, some beneficial and some harmful. When
    the balance between the two is disrupted, it can affect the
    barrier function of the intestinal wall (1, 8).
  • Yeast overgrowth: Yeast is naturally present
    in the gut, but an overgrowth of yeast may contribute to
    leaky gut (18).

Summary: Medical professionals are still
trying to determine what causes leaky gut syndrome. An
unhealthy diet, long-term NSAID use, stress and chronic
inflammation are some factors that are believed to contribute
to it.

Diseases Associated With Leaky Gut

The claim that leaky gut is the root of modern health problems
has yet to be proven by science. However, many studies have
connected increased intestinal permeability with multiple
chronic diseases (3).

Celiac Disease

Celiac disease is an autoimmune disease characterized by a
severe sensitivity to gluten.

Several studies have found that intestinal permeability is
higher in patients with celiac disease (1, 6, 7).

In fact, one study found that ingesting gluten significantly
increases intestinal permeability in celiac patients
immediately after consumption (6).

Diabetes

There is some evidence that increased intestinal permeability
plays a role in the development of type 1 diabetes (1).

Type 1 diabetes is caused by an autoimmune destruction of
insulin-producing beta cells in the pancreas (19).

It has been suggested that the immune reaction responsible for
beta cell destruction may be triggered by foreign substances
“leaking” through the gut (20, 21).

One study found that 42% of individuals with type 1 diabetes
had significantly elevated zonulin levels. Zonulin is a known
moderator of intestinal permeability (22).

In an animal study, rats that developed diabetes were found to
have abnormal intestinal permeability prior to developing
diabetes
(23).

Crohn’s Disease

Increased intestinal permeability plays a significant role in
Crohn’s disease. Crohn’s is a chronic digestive disorder
characterized by persistent inflammation
of the intestinal tract (1, 24, 25).

Several studies have observed an increase in intestinal
permeability in patients with Crohn’s disease (26, 27.)

A few studies also found increased intestinal permeability in
relatives of Crohn’s patients, who are at an increased risk of
developing the disease (26, 28).

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This suggests that increased permeability may be connected to
the genetic component of Crohn’s disease.

Irritable Bowel Syndrome

Studies have found that people with irritable bowel syndrome
(IBS) are likely to have increased intestinal permeability
(29, 30).

IBS is a digestive disorder characterized by both diarrhea and
constipation. One study found that increased intestinal
permeability is particularly prevalent in those with
diarrhea-predominant IBS (31).

Food Allergies

A few studies have shown that individuals with food
allergies
often have impaired intestinal barrier function
(32, 33).

A leaky gut may allow food proteins to cross the intestinal
barrier, stimulating an immune response. An immune response to
a food protein, which is known as an antigen, is the definition
of a food allergy (10).

Summary: Multiple studies have demonstrated
that increased intestinal permeability is indeed present in
people with certain chronic diseases.

Is Leaky Gut a Cause or Symptom of Disease?

Woman in a Red Shirt Holding Her Stomach

Proponents of leaky gut syndrome claim it’s the
underlying cause
of most modern health problems.

Indeed, plenty of studies have shown that increased intestinal
permeability is present in several chronic diseases,
specifically autoimmune disorders.

However, it is difficult to prove that leaky gut is the
cause of disease.

Skeptics argue that increased intestinal permeability is a
symptom of chronic disease, rather than an underlying cause
(34).

Interestingly, animal studies on celiac disease, type 1
diabetes and IBS have identified increased intestinal
permeability prior to the onset of disease (23, 34, 35).

This evidence supports the theory that leaky gut is involved in
the development of disease.

On the other hand, a study found that intestinal permeability
in people with celiac disease returned to normal in 87% of
people who followed a gluten-free diet for over a year. A
gluten-free
diet
is the standard treatment for celiac disease (36).

This suggests that the abnormal intestinal permeability may be
a response to gluten ingestion, rather than the cause of celiac
disease.

Overall, there is not yet sufficient evidence to prove that
leaky gut is the underlying cause of chronic diseases.

Summary: Studies have consistently shown
that increased intestinal permeability is present in several
chronic conditions. However, there is no conclusive evidence
that leaky gut is the underlying cause of them.

Some Claims About Leaky Gut Syndrome Are Not Backed by Science

There is enough evidence to demonstrate that leaky gut syndrome
does exist. However, some of the claims being made are not
backed by science.

Proponents of leaky gut have claimed that it’s connected to a
wide variety of ailments, including autism, anxiety,
depression, eczema and cancer. Most of these claims have yet to
be proven by scientific studies.

A few studies have found that a proportion of autistic children
have increased intestinal permeability, but other studies have
found that intestinal permeability was normal (37, 38, 39).

Currently, there are no studies that show leaky gut presence
prior to the onset of autism, which means there is no evidence
that it is a causative factor.

There is some evidence that bacteria crossing the intestinal
wall may play a role in anxiety and depression, but more
research is needed to prove this possible connection (40, 41, 42).

The results of studies on eczema and intestinal permeability
have been inconsistent, and there is currently no scientific
basis for the claim that leaky gut leads to cancer (43, 44, 45).

Furthermore, some of the proposed treatments for leaky gut
syndrome have weak scientific support.

Many supplements and remedies being sold by websites have not
yet been proven to be effective (34).

Summary: There is sufficient evidence to
demonstrate that leaky gut syndrome exists. However, science
has not yet proven that conditions like autism or cancer are
related to leaky gut syndrome.

How to Improve Your Gut Health

Yogurt With Blueberries

Leaky gut syndrome is not an official medical diagnosis and
there is not yet a recommended course of treatment.

Nevertheless, there are steps you can take to improve your gut
health. One of the keys to a healthier gut is increasing the
number
of beneficial bacteria
in it.

Here are a few strategies to support a healthy gut:

  • Limit your refined carb intake: Harmful
    bacteria thrive on sugar, and excessive sugar intake can harm
    gut barrier function (8, 9, 46).
  • Take a probiotic supplement: Probiotics are
    beneficial bacteria that can improve your gut health.

    Probiotic supplements
    have been shown to be beneficial
    for gastrointestinal diseases (47, 48, 49, 50, 51).
  • Eat fermented foods: Fermented foods, such
    as plain yogurt, kimchi, sauerkraut, kefir and kombucha,
    contain probiotics that can improve gut health (49, 52, 53).
  • Eat plenty of high-fiber foods: Soluble
    fiber, which is found in fruits, vegetables and legumes, feed
    the beneficial bacteria in your gut (8, 54, 55).
  • Limit the use of NSAIDs: The long-term use
    of NSAIDs like ibuprofen contributes to leaky gut syndrome
    (10, 11, 12).

Summary: Increasing the friendly bacteria in
your gut can improve your gut health and help prevent leaky
gut syndrome.

The Bottom Line

Leaky gut, or increased intestinal permeability, is a condition
in which bacteria and toxins are able to pass through the
intestinal wall into the bloodstream.

Some medical professionals deny that leaky gut exists, but
there is quite a bit of evidence to confirm that increased
intestinal permeability is real.

For example, leaky gut syndrome is present in several
autoimmune disorders.

However, there is not enough evidence to conclude that leaky
gut syndrome is the underlying cause of these diseases.

To decrease your risk of leaky gut syndrome, focus on improving
your gut health by eating a healthy diet and limiting your use
of NSAIDs.

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