A gastrointestinal condition called “leaky gut” is gaining worldwide attention, particularly among the natural health community.

Some medical professionals deny that leaky gut exists, while others claim it is the root of nearly every disease.

Leaky gut is somewhat of a medical mystery. Scientists are still trying to determine exactly what it is and what causes it. Some people think that gluten causes leaky gut, but the role of gluten in the condition is complicated.

This article examines the research about gluten and leaky gut syndrome.

What Is Gluten?

Gluten is a mixture of proteins found naturally in grains like wheat, barley and rye.

It is responsible for the elastic nature of dough, which helps the dough hold together and rise. Gluten is also what gives bread its chewy texture (1).

It is also sometimes added to bread dough to increase its ability to rise.

The two major proteins that make up wheat gluten are gliadin and glutenin. Gliadin is the portion of the gluten that some people react negatively to.

Bottom Line:

Gluten is a group of proteins found in wheat, barley and rye. One of these proteins causes negative health effects in some people.

What Is Intestinal Permeability?

The digestive system performs several very important functions in your body.

The digestive tract is where food is broken down and nutrients are absorbed into the bloodstream.

The walls of the intestines also serve as an important barrier between the gut and the rest of the body.

The intestinal wall serves as a gatekeeper, determining which substances pass through to the bloodstream and organs.

Intestinal permeability is a term that describes how easily substances pass through the intestinal wall. Normally, there are tiny gaps between the cells in the small intestine called tight junctions.

If these are damaged or become too loose, it causes the gut to become “leaky,” allowing substances and organisms in the gut to leak into the bloodstream.

This phenomenon of increased intestinal permeability is also known as leaky gut syndrome. When bacteria and toxins are leaking into the bloodstream, it causes widespread inflammation in the body.

Increased intestinal permeability has been implicated in autoimmune diseases including type 1 diabetes, Crohn’s disease and inflammatory skin disorders (2, 3, 4).

Bottom Line:

When the barrier function of the small intestine is impaired, bacteria and toxins can leak from the gut, causing inflammation and disease.

Gluten Causes Significant Problems for Some

Most people are able to digest gluten just fine.

That said, a small proportion of people cannot tolerate it.

The most severe form of gluten intolerance is called celiac disease. Celiac is a hereditary autoimmune disease.

For individuals with celiac disease, gluten can cause diarrhea, stomach pain, excessive gas and skin rashes. Over time, it can cause damage to the intestines, which impairs their ability to absorb certain nutrients (5, 6).

However, some people test negative for celiac disease but still react to gluten. This is referred to as non-celiac gluten sensitivity.

The symptoms are similar to celiac disease, but without the autoimmune response. People with non-celiac gluten sensitivity may experience diarrhea, bloating and gas, along with joint pain and brain fog (7).

There is currently no clinical method of diagnosing non-celiac gluten sensitivity. If you react negatively to gluten and your symptoms are relieved with a gluten-free diet, you probably have gluten sensitivity (8, 9, 10).

The topic of gluten remains highly controversial. Some medical professionals believe that gluten is harmless unless you have celiac disease. Others claim that gluten is the root cause of all kinds of health problems and autoimmune disorders.

Bottom Line:

Most people can tolerate gluten just fine. However, gluten causes significant problems in sensitive individuals.

Gluten Activates Zonulin, the Regulator of Intestinal Permeability

Several studies have shown that gluten can increase intestinal permeability and cause an immune response in the body (11).

The immune system responds to substances it recognizes as harmful by causing inflammation. Inflammation is the body’s natural self-protection mechanism, but persistent inflammation is associated with multiple chronic diseases.

In sensitive individuals, gluten is deemed a foreign invader, leading to inflammation. However, there is conflicting evidence regarding gluten and intestinal permeability.

How Gluten Affects Zonulin and Gut Permeability

Zonulin is a protein that regulates the tight junctions of the small intestine. When zonulin is released in the intestines, the tight junctions open slightly and allow larger particles to pass through the intestinal wall (12, 13).

Test-tube studies have found that gluten activates zonulin, which leads to increased intestinal permeability (14, 15).

One of these studies found that gluten activated zonulin in cells from individuals with and without celiac disease. However, zonulin levels were much higher in cells from celiac patients (14).

How Does This Affect People With Gluten Sensitivity?

Studies have consistently demonstrated that gluten significantly increases intestinal permeability in celiac patients (16, 17, 18).

There are mixed results when it comes to individuals without celiac disease. Test-tube studies have shown that gluten increases intestinal permeability, but this has not been confirmed in human studies (17).

One clinical study also found that gluten increased intestinal permeability in patients with irritable bowel syndrome (IBS) (19).

However, in other human studies, gluten did not cause any changes to intestinal permeability in those with non-celiac gluten sensitivity or IBS (20, 21).

Individual Health May Play a Role

Gluten does activate zonulin, but it does not affect everyone the same way.

It is clear that gluten does increase intestinal permeability in those with celiac disease and possibly in those with IBS. However, it appears that gluten does not increase intestinal permeability in healthy people.

Bottom Line:

Gluten activates zonulin and increases intestinal permeability in people with celiac disease. Gluten does not increase intestinal permeability in healthy people.

Factors That Contribute to Leaky Gut Syndrome

Gluten may play a role in the development of leaky gut syndrome in those with celiac disease or IBS, but it is certainly not the only cause.

Medical professionals are still trying to understand exactly what causes leaky gut syndrome, but there are a few factors that are known to contribute to the condition.

Here are some of the contributing factors:

  • Unhealthy diet: A diet high in fat and refined carbs may increase intestinal permeability (22, 23, 24).
  • Stress: Prolonged stress can alter the gut-brain interaction and lead to all kinds of gastrointestinal issues, including increased intestinal permeability (25).
  • Non-steroidal anti-inflammatory drugs (NSAIDs): Overuse of NSAIDs, such as ibuprofen, can increase intestinal permeability (26, 27).
  • Inflammation: Chronic widespread inflammation contributes to multiple chronic diseases, as well as increased intestinal permeability (28).
  • Poor gut flora: When the balance between the beneficial and harmful bacteria lining the gut is compromised, it can contribute to leaky gut syndrome (2, 24).
  • Zinc deficiency: A lack of zinc in the diet can alter intestinal permeability and contribute to multiple gastrointestinal problems (29).
  • Yeast: Yeast is naturally present in the intestinal tract. When the growth of yeast, mainly Candida, gets out of hand, it causes problems (30).
Bottom Line:

There are many factors that contribute to the development of leaky gut syndrome. In those with celiac disease or IBS, gluten may be a contributing factor.

Should Everyone Avoid Gluten?

Gluten causes significant problems for some people.

For individuals with celiac disease, gluten increases intestinal permeability and triggers the autoimmune response and inflammation.

However, the relationship between gluten and intestinal permeability is complex and not yet clearly understood.

Currently, there is no solid evidence to support that gluten increases intestinal permeability or causes leaky gut in healthy people.

If you have symptoms of gluten sensitivity, it may be beneficial to remove gluten from your diet. You can read more about eating gluten-free here.

Bottom Line:

Those with celiac disease or gluten sensitivity should avoid gluten. However, there is no significant evidence that healthy people need to avoid gluten.

Factors That Can Improve Your Gut Health

One of the keys to improving your gut health and preventing leaky gut syndrome is to improve your gut flora. That means increasing the beneficial bacteria in your gut so they far outnumber the harmful bacteria.

Here are some ways to improve your gut health:

  • Take probiotics: Probiotics are beneficial bacteria that can improve gut health. Probiotics are found in foods like yogurt, kefir, sauerkraut and kimchi. They are also available in a supplement form (31, 32, 33).
  • Avoid refined carbs: Avoid sugar-sweetened beverages and foods with added sugars or refined wheat flour. The harmful bacteria in your gut thrive on these foods (22).
  • Eat plenty of fiber-rich foods: Fruits, vegetables and legumes are high in soluble fiber, which feeds the good bacteria in your gut (34, 35).
Bottom Line:

Increasing the beneficial bacteria in your gut may improve your gut health and help prevent leaky gut syndrome.

Take Home Message

Gluten causes significant problems for sensitive individuals.

Research shows it can increase intestinal permeability, also known as leaky gut, in people with celiac disease and possibly IBS.

However, this does not appear to be the case for healthy people.

If you think you have symptoms of gluten sensitivity, it may be beneficial to talk to your doctor and consider trying a gluten-free diet.