Probiotics for Leaky Gut: Do They Work?

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Probiotics for leaky gut are a big focus area for research right now.  This is because our microscopic copilots, known as our microbiome, may dictate much of our health.

The diversity and number of bacteria, as well as fungi and commensal viruses, largely control our immune system, inflammation, and more. These microorganisms can hurt OR help a leaky gut [R].

The effects of a leaky gut may often extend to thyroid health as well.

Continue reading to find out if probiotics are right for you and your patients.

Probiotics for Leaky Gut: Do They Work | Thyroid Nutrition Educators

What is a Leaky Gut?

Our epithelial barrier, or tight junctions of the intestinal wall, are one cell thick.  Talk about a fragile and yet precarious digestive system [R]!

These tight junctions in the intestinal wall are the single barrier between our intestinal world and the rest of our body.  It is essential for health that this barrier wall is functioning well, or health, hormone balance, and homeostasis will suffer [R].

When the barrier wall is compromised, it is referred to as a leaky gut.

Tight junctions in our intestinal tract are gaining a lot of research and we know that a compromise and an increased intestinal permeability is a trigger for inflammation throughout our entire body [R].

Why Worry About a Leaky Gut?

Leaky gut is thought to be at the root of systemic inflammation and may play a role in the causes of [R]:

  • Autoimmune diseases
  • Pain
  • Neurodegenerative disorders
  • Hormone imbalances
  • Irritable bowel syndrome
  • Inflammatory bowel disease
  • Mood disorders

When unwanted compounds enter the body due to a leaky gut, the innate immune system may trigger widespread inflammation [R].

The inflammatory response in these disorders may be as a result of endothelial dysfunction or a compromise of tight junctions. Bacterial metabolic components then translocate or diffuse systemically.  They may even pass the blood-brain barrier and reach cerebral spinal fluid [R].

For example, a leaky gut may explain the neurological complications of celiac disease.

The easiest way to remember this phenomenon is to remember that a leaky gut results in a loss of immune tolerance.  We react to substances that otherwise wouldn’t be in high numbers in the blood, such as bacterial remnants and related lipopolysaccharides.

What Causes a Leaky Gut?

As the world has become more hygienic and processed, our guts have become leakier [R]. While no one knows for sure if this is causal, the steady climb of inflammatory diseases related to gut dysfunction can’t be just about genetics.

Research does show that the effects of diet and lifestyle factors may play a role in epithelial barrier dysfunction.  Causes of leaky gut include:

  • Medicines
    • Antibiotics and NSAIDS
    • Steroids and birth control
    • Proton pump inhibitors
    • Chemotherapy
  • Inadequate amounts of good bacteria
  • Low diversity of different types of bacteria
  • Processed foods and inflammatory foods
  • Food Sensitivities
  • Inadequate micronutrients
  • Toxins

Our small intestinal tight junctions interact every second of the day with the trillions of microbes in our intestinal wall or lumen [R].

This system gets disrupted by so many medications and food imbalances.  As a result, our bodies can go into high alert.

How Does Leaky Gut Occur?

Dysbiosis, or imbalances in the microbiome, happens when the gut bacteria numbers and types are altered by diet, stress, medications, and toxins.

The tight junctions are then disturbed by this imbalance because the healthy bacteria aren’t able to protect our endothelial wall from the harmful bacteria.

The tight junctions become damaged from the harmful invaders, and this creates an opening for small bacterial particles, viruses, and incompletely digested food particles to enter into our circulation.

How Does a Leaky Gut Affect the Thyroid

As previously mentioned, our intestinal epithelial cells are only one cell layer thick.

Right below this layer is the lamina propria, where our effector immune cells reside.  Effector cells dictate a lot of immune functions.

When the epithelial cells are compromised, like in the case of the leaky gut, this can cause a very immune reactive cascade in the body, beginning with antigens from within the gut.  This barrier dysfunction is believed to drive autoimmune disease [R].

These related autoimmune diseases in the thyroid include Hashimoto’s thyroiditis and Grave’s disease.

A good example of how the leaky gut is connected with the thyroid is celiac disease.  This disorder results in leaky gut and has a lot in common with autoimmune thyroid diseases.  For example, celiac disease and thyroid diseases share genes, shared imbalance in the microbiome, and ties to a leaky gut [R].

How to Know if Your Clients Have a Leaky Gut

While there is no one single diagnostic symptom, the following can help you hone in on people who may benefit from looking at their health from the leaky gut perspective.  These symptoms include:

  • Bloating and gas
  • Abdominal pain
  • Constipation or diarrhea
  • Asthma or allergies
  • Hormone imbalances
  • Autoimmune diseases
  • Thyroid issues
  • Fibromyalgia
  • Chronic pain
  • Candida infection
  • Mood disorders
  • Skin issues like eczema or psoriasis, acne
  • Weight gain

Your patients may have just a few or many of these symptoms and issues.  Regardless, it is important to know that these symptoms aren’t just limited to the digestive tract.

Digestive distress is a signal that the microbiome is out of balance.  It is important to explore food sensitivities, nutritional quality, and medication history to help your patients most.  Read about this approach in our functional nutrition post.

How is Leaky Gut Diagnosed?

There are a number of tests available to help determine if a leaky gut is contributing to your clients’ health.  However, keep in mind, each test has its limitations as follows [R]:

[supsystic-tables id=1]

In our experience, a careful diet history and symptoms checklist are just as useful, and likely, the treatment could be similar.

Do Probiotics Affect a Leaky Gut?

Leaky gut syndrome plays a role in the cause of inflammatory bowel diseases as well as irritable bowel syndrome [R].

Over 80 clinical studies in humans show that probiotics are a reasonable option in diseases affected by inflammatory bowel diseases. This includes inflammatory bowel diseases like ulcerative colitis.

For irritable bowel syndrome, the results of using lactobacillus probiotics are beneficial in clinical studies.  A review of 70 clinical trials found that lactobacillus probiotics reduced IBS symptoms [R].

Unfortunately, probiotics at this point haven’t shown many benefits for people with Crohn’s disease, while fecal transplants are showing promise for this condition [R].  It could bet that clinical trials in Crohn’s disease so far aren’t at high enough concentrations or diverse enough in bacterial strains to provide meaningful results.

In this review, it also concluded that probiotics not only help reduce symptoms but can help eradicate antibiotic-associated diarrhea and H.Pylori infections.

But How Do Probiotics Work?

Probiotic bacteria that reside in our gut do so much for our health-related to our gut lining. They help:

  • Increase nutrients: many strains of lactobacillus, like Lactobacillus reuteri increase the synthesis of folate, vitamin B12, and other B vitamins [R]
  • Reduce harmful invaders:  antimicrobial activity by making bacteriocins and reducing viral and bacterial gene expression,  competition for binding sites, and increase in secretory IgA and regulation of cytokines [R].
  • Reduce zonulin: A marker of gut permeability, zonulin was decreased in trained athletes after receiving Omnibiotic, multi-strain probiotics compared to placebo [R].
  • Reduce inflammation: probiotics make anti-inflammatory compounds and are involved in cholesterol and fat homeostasis [R]
  • Help fuel the gut: By making short-chain fatty acids like butyrate and proprionate, probiotics help nourish the brush border [R].
  • Support the mucin lining: certain probiotic strains, like Lactobacillus plantarum 299v, E. Coli Nissle 1917, and Lactobacillus Casei GG, help increase mucin protein expression and gene expression [R].
  • Regulate tight junctions: probiotics like Lactobacillus and Bifidobacterium increase the expression of tight cell junction proteins [R].
  • Support immune function:  People taking probiotics had fewer colds and influenza compared to placebo over a 12 week study period [R].

Leaky Gut and Non-Alcoholic Fatty Liver Disease (NAFLD)

To further solidify the connections between leaky gut and health, we have the example of Non-Alcoholic Fatty Liver Disease (NAFLD), which is benefited by probiotics. In NAFLD, there is an influx of bacteria and bacterial products.  This is thought to contribute to the fat accumulation and tissue inflammation within the liver.

Further, giving probiotics is showing great benefits for people who have NAFLD [R].

In acutely ill patients, leaky gut is often considered a culprit in the cause of sepsis complications as well.

Bottom line: probiotics for leaky gut may also extend benefits to NAFLD.

Can Probiotics Cause Harm?

Probiotics supplements are among the best supplements for leaky gut.  They also are generally safe but can cause some transient increase in digestive distress such as gas and bloating.  Don’t worry necessarily; this can mean they are working.  These symptoms typically subside after a week or two.

Some people are sensitive to the histamine that probiotics make.  However, some strains of probiotics can actually decrease histamine levels.

People can also react to other ingredients in probiotics, such as lactose or prebiotic fibers.

Probiotics should not be given to people who are having severe, acute pancreatitis  [R].

Also, a very important consideration:  your client’s individuality.  There are likely some people who respond better to some strains than others.

Probiotic Foods

Lactobacillus-containing probiotic foods are very helpful for many people for symptom management of digestive disorders.

These foods can include most fermented foods like fresh sauerkraut, kimchi, kvass, gherkin pickles that are fermented, apple cider vinegar, kombucha, coconut yogurt, raw vegetables, and more.

Best Probiotics for Leaky Gut

It is important to remember that research uses may different bacterial strains, combinations, and amounts of probiotic bacteria. When choosing a probiotic keep all of the following in mind:

  • Diversity of strains
  • Combination of strains
  • Type of bacteria
  • Amount of each strain
  • Brand reputation and quality

Bifidobacterium strains

  • Bifidobacterium infantis
  • Bifidobacterium lactis
  • Bifidobacterium longum
  • Bifidobacterium brevo

These strains have been shown to improves the gut barrier function and attenuated bacterial and endotoxin translocation and protected the mucin lining in a review of the research article in Current Nutrition Food Science [R].

Zonulin occludins and claudin are proteins involved in the formation of tight junctions. They are also known as scaffolding proteins.

Clinical study on Bifidobacterium lactis

Bifidobacterium lactis has been found to improve digestive symptoms in people with minor digestive symptoms compared to placebo

The probiotic Bifidobacterium lactis found in fermented milk resulted in improved digestive symptoms and overall gastrointestinal (GI) health among women with digestive discomfort.

To further assess these results, a second clinical double-blind, controlled study was carried out among women with diagnosed GI conditions.

Two groups were assessed for weekly Probiotic fermented milk or controlled dairy product was consumed and digestive symptoms were assessed weekly over a 4 week period.

Findings from the second trial showed no significant difference in the percentage of women showing an improvement in GI health. Digestive symptoms were also significantly reduced when compared to the control group.

Overall, with pooled analysis from both trials, the women reported improved GI well-being and a reduction in digestive symptoms [R].

Lactobacillus strains

  • Lactobacillus paracasei
  • Lactobacillus salivarius
  • Lactobacillus rhamnosus
  • Lactobacillus fermentum 
  • Lactobacillus plantarum

These strains, improve digestion, boosts immune response, help fight infection and reduces the growth of pathogenic bacteria. Lactobacillus strains, including L. rhamnosus GG, prevents the alteration of tight junctions due to dysbiosis [R].

Clinical study on Lactobacillus acidophilus

Lactobacillus acidophilus-SDC 2012, 2013 are new strains of acidophilus isolated from Korean infants’ feces.

These strains have been studied as a remedy for irritable bowel syndrome (IBS).

Half of the 40 patients given these strains of acidophilus were found to have reduced abdominal pain or discomfort after four weeks of treatment when compared with the control group.

This illustrated there was a beneficial effect of Lactobacillus acidophilus-SDC 2012, 2013 in patients with IBS [R].


Saccharomyces species are a type of yeast; some strains function as probiotics to protect tight junctions.  These include:

  • Saccharomyces cerevisae
  • Saccharomyces boulardii

S. cerevisae promotes the formation of tight junctions, prevents bacterial translocation, and improves immune response in animal models [R] [R].

Clinical study Saccharomyces cerevisae

This trial aimed to evaluate symptoms in those with irritable bowel syndrome after taking Saccharomyces cerevisiae.

One hundred and seventy-nine adults with IBS were given 500 mg capsule of Saccharomyces cerevisiae or a placebo for eight weeks followed by a 3-week washout period.

Those given Saccharomyces cerevisiae had improvement in abdominal pain and discomfort. Bloating, distension, bowel movement difficulty were also decreased in those who were given the probiotic.

Along with reducing abdominal pain Saccharomyces cerevisiae areduce was well tolerated and did not change stool consistency  [R].

Clinical study Saccharomyces boulardii

S. boulardii is a nonpathogenic yeast that has been used in Europe to prevent antiobiotic associate diarrhea (AAD).

A double-blind controlled study was designed to investigate the effect of S. boulardii on AAD.

This 23-month study included 180 hospitalized patients who were suffering from AAD were placed into two groups: one group was given 250 mg S. boulardii in capsule form twice a day with other group receiving a placebo.

Of the patients receiving the placebo, 22 percent experienced diarrhea compared with 9.5 percent of patients who received S. boulardii.

S. boulardii did not have any side effects following treatment and only one person, who was on the placebo mentioned diarrhea after the study [R].

The true mechanism of how S. boulardii prevents AAD is unknown, however, previous studies show several properties of yeast have been found to fight against bacterial pathogens and candida.

In both rats and humans, S. boulardii is thought to improve carbohydrate absorption by increasing the digestive enzyme disaccharidase in the intestinal mucosa [R,R].

However, one thing to note is that when tested this strain of bacteria was not effective at preventing antibiotic-associated diarrhea in elderly hospitalized patients, so depending on the age of your patient you may need to use another type of probiotic strain [R].

Escherichia coli

One strain of E. coli shows benefit as a probiotic for leaky gut.  It is called E. coli Nissle 1917. This strain protected the tight junctions by increasing the production of zonulin occludin 1, increased T84 barrier function, and increased resistance to pathogens [R].

Probiotic Combinations

Many people are familiar with the research of the probiotic called VSL#3. This probiotic is a combination of most of the strains previously described.  VSL#3 is now marketed as Visbiome

VSL#3 (L. casei, L. plantarum, L. acidophilus, L. delbrueckii, B. longum, B. infantis, B. brevo and Streptococcus salivarius) was able to decrease claudin and zonulin occludin redistribution in acute colitis in animal studies [R].

Symprove Multi-strain for reducing IBS in clinical research. Includes Lactobacillus rhamnosus NCIMB 30174, Lactobacillus plantarum NCIMB 30173, Lactobacillus acidophilus NCIMB 30175 and Enterococcus faecium NCIMB 30176 [R].

Other strains:

Bacillus clausii is effective for adjuvant H.Pylori treatment. Incidences of nausea, diarrhea, and epigastric pain were lower in patients receiving B. clausii when compared with the placebo group [R].

How Much Probiotic for Leaky Gut?

As a general rule, the higher the diversity of strains and the larger the number of colony-forming units a probiotic has, the more potent it is.  Unfortunately, however, no formal dosing guidelines are available at this time.

On the market, you can find probiotics as little as 1 billion CFU and as much as 120 billion CFU per capsule.

Experts often suggest that clients aim for at least 20-50 billion CFU per day.

It goes without saying that you would want a different dose for an infant or a small child than a grown adult. Many brands are available with a targeted age group in mind.

When to Take Probiotics?

Research studies vary quite a bit in how probiotics are given.

  • They often give probiotics on an empty stomach, allowing participants to eat within 20 to 30 minutes of taking the probiotic supplement.
  • Some research does not specify the timing of probiotics.
  • Many studies give probiotics multiple times a day.

Bottom line: It is unknown the best timing of taking probiotics, but what appears to be clear is that taking the probiotic is beneficial for digestive issues.

How Long to Take Probiotic for Leaky Gut?

Most research studies give probiotics for a minimum of one month and are up to 12 months in duration.

It is unknown how long to take probiotics for leaky gut, but as long as your client feels better, it can’t hurt to take them.

Delayed Release: Does it Matter?

In theory, delayed-release capsules help bypass the acidity of the stomach, allowing a better chance of the probiotics to take residence in the small intestine.

Some brands sell delayed-release capsules.  It is unknown whether or not they are superior to other brands.  Clinical studies usually do not use delayed-release capsules.

Can Probiotics Harm Leaky Gut?

In short, no research has shown that probiotics harm leaky gut.

Keep in mind, we have around 39 trillion bacteria residing in our digestive tract and the complexity is vast [R].

Individual responses to probiotics will vary a lot, as our bacteria in our gut are like our own blueprint.

Be wary of using probiotics in the following settings:

  • Severe, acute pancreatitis
  • Critically ill patients in the intensive care unit
  • Prolonged immune compromise, such as people on immuno-suppressive drugs.

Prebiotics and Postbiotics

Prebiotics are usually a soluble type of fiber that helps support the growth of beneficial bacteria.

Postbiotics are beneficial metabolic products of pre-and probiotics.  They include short-chain fatty acids like butyrate, acetic acid, inactivated probiotics, enzymes, vitamins, amino acids, nitric oxide, and neurotransmitters, to name a few [R].

The use of postbiotics in research is still early but is promising for use in people with a leaky gut. Postbiotics can include heat-inactivated probiotics, such as Lactobacillus strains.  Their effects are not inferior to the live probiotics themselves [R].

Fiber in the diet should serve as the primary prebiotic for everyone.  Fiber helps to form short-chain fatty acids like butyrate, which provide fuel for the epithelial barrier.  They also provide fuel for probiotics to help live in the intestines.

Research is emerging, but still inconclusive about supplementing prebiotics for a leaky gut [R].

Standards for Selecting the Best Probiotics

  • Efficacy —efficacy of a brand can be determined by the previous clinical research available about doses and strains.
  • Independent lab verification — also known as third party testing and good manufacturing practices certification or GMP certification.  This helps ensure potency, purity, and efficacy.
  • Prebiotic content —for some clients, you will want to have prebiotics as well. Be aware that some people with digestive issues don’t always tolerate prebiotic fibers.  It is best to individualize this for your clients.

The Probiotic Brands that Meet the Standards*


Visbiome is formerly known as VSL#3, clinically studied probiotic with 112 billion CFU, multistrain as described above.

Orthobiotic Capsules

These probiotics are a blend of active organisms to help improve the diversity of microflora to help strengthen the intestinal wall. Some Ortho Biotic brands include the following:

  • Douglas Laboratories multi-strain with 40 billion CFU, rigorous 3rd party testing
  • Ohhira’s Probiotics is a three-year fermented food supplement with probiotics, prebiotics, and postbiotics
  • Culturelle is a 10 billion CFU L. rhamnosus GG per capsule, taken twice daily
  • Ortho Biotic by Ortho Molecular Products is a blend of 20 Billion CFU L. acidophilus, L. paracasei , B. lactis, B. bifidum, L. plantarum, L. rhamnosus, and 3 Billion CFU of S. boulardii

*Some of these links are affiliate links, this means when you sign up or purchase from these links we may receive a small commission at no extra cost to you. Learn more in our disclosure statement.

Leaky gut diet plan

While probiotics appear helpful for digestive issues, including leaky gut, the quality of the diet is very important for leaky gut repair [R].

For your clients, consider the following:

  • Removal
  • Repair
  • Restore
  • Reinoculate

Removal of intolerances, processed foods

Repair-using clinical judgment, herbs, and supplements like l-glutamine, ginger, etc for GI support.

Restore with adequate micronutrients like vitamin D3, zinc, and vitamin A supplementation when needed.

Reinoculate-using probiotics, fermented foods, and prebiotics

Ferment your own foods and learn how to make natto and other foods like sauerkraut.


While we can’t rely alone on supplements to heal a leaky gut, they can play an important role in digestive health.  Supplements of probiotics benefit symptoms of a leaky gut in clinical trials.  As with any supplement, make sure to carefully evaluate each person with a detailed diet history, medication history, and exposure to toxins history.

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7 thoughts on “Probiotics for Leaky Gut: Do They Work?”

  1. This is such a great resource – I get questions about this all the time! I love the table that you created – and all the clinical studies; thank you!

  2. Thanks for this comprehensive review of probiotics. It’s so important to work with a trusted professional on issues like this.

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