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Saccharomyces boulardii: the antibiotic resistant probiotic

Article at a Glance
  • Saccharomyces boulardii (S. boulardii) is a strain of non-pathogenic yeast first discovered in French Indochina by Henry Boulard in 1920.
  • S. boulardii has been shown in multiple clinical trials to benefit human health, including reducing the incidence of antibiotic associated and traveler’s diarrhea.
  • Because S. boulardii is a yeast microbe, it cannot be killed by antibiotics and is an ideal supplement to pair with antibiotics.
  • S. boulardii has been shown to be effective at combating Candida Albicans, H. Pylori, Clostridium Difficile, and other pathogenic yeast and bacteria strains.
  • The highest-quality S. boulardii preparations are lyophilized (freeze-dried) and generally contain 5 billion CFU (colony forming units).
Genes Mentioned
saccharomyces boulardii

Science Score:

Like many people, I came across Saccharomyces boulardii (S. boulardii) while I was forced to take a course of antibiotics. As I began to do my research, I realized that this crazy little probiotic yeast is one of the most proven supplements on the market today, with hundreds of peer reviewed studies proving efficacy.

(Warning, poo disclosures on the way).

Once I began with S. boulardii, I noticed an immediate, significant improvement in digestion and stool consistency, even while on antibiotics. Amber, another Gene Food contributor, gets squeamish when blog posts discuss poo, but who are we kidding?

I don’t take S. boulardii everyday, instead like most probiotics I use, I cycle it, taking S. boulardii for a week or two when I feel my body needs it.

I am going to do a thorough break down of S. boulardii’s benefits in a moment, but one of the most interesting for me is S. boulardii’s ability to beat back Candida. Candida is a pathogenic yeast that is found in everyone’s intestinal tract, but it can run amuck and proliferate beyond healthy levels when our gut flora is disturbed, as it can be when we’re drinking a lot, or when we take a course of antibiotics.

S. boulardii has been shown effective at killing Candida, and suppressing expression of the inflammatory markers it produces. (R) (R) Since Candida overgrowth is relatively common, S. boulardii is a probiotic that many people will be able to benefit from at some point in their lives.

S. boulardii basics

S. boulardii is a non-pathogenic yeast microbe that has been proven in multiple randomized clinical studies to be effective as a probiotic, especially in the treatment of antibiotic induced diarrhea, traveler’s diarrhea, and other inflammatory bowel conditions. S. boulardii has even been shown to increase serum IgA levels in mice which has led researchers to speculate that S. boulardii may have potential for boosting the strength of the human immune system.

Because S. boulardii is a yeast microbe, it is not killed by antibiotics, and can be taken directly alongside a course of antibiotics. (R) So, how did S. boulardii come to be used as a dietary supplement?

The story starts in French colonial days. 

History of Saccharomyces boulardii

The French scientist Henry Boulard first discovered S. boulardii in 1920 after observing that certain locals in IndoChina were not succumbing to an outbreak of cholera. The healthier locals drank a tea made of the skins of lychee and mangosteen, from which Boulard was able to isolate S. boulardii as the protective yeast. The strain has been named after him ever since its discovery. 

Choosing a high-quality S. boulardii product

Before we delve into the studies examining the efficacy of S. boulardii as a probiotic, it’s important to note that not all strains of S. boulardii are created equal.

The efficacy of products on the market can vary greatly depending on the quality of the manufacturing process, and label claims on many popular probiotics are often inaccurate. (R) S. boulardii supplements are available in capsules of either lyophilized (freeze dried) or heat-dried preparations. You can usually tell when a probiotic is heat dried because the label will tell you to refrigerate the bottle, or the bacteria will lose potency. I used to think that probiotics that required refrigeration were the highest quality.

I now know that the opposite is true. Lyophilized probiotic preparations are stable at room temperature and do not require refrigeration.

In the case of S. boulardii, and many other strains, it is important to look for products that have lyophilized preparation as studies have shown that lyophilized capsules have much greater potency than heat-dried products that require refrigeration. (Schwenzer V.B. (1998) Saccharomyces boulardii. Deutsche Apotheker Zeitung 138: 75–77)

As we have been getting questions in the comments about different S. boulardii preparations, I decided to give a run down of three popular brands you can buy on Amazon. As a general rule, and in addition to finding a product that is stable at room temperature, a good S. boulardii product will have a high CFU count. What is CFU? It stands for “colony forming unit,” which represents the number of live bacteria or yeast in a given sample. Good quality S. boulardii products will generally contain 5 billion CFU or greater.

S. boulardii brand comparison

BrandCFULyophilizedAdditionsQuantity
Jarrow Formulas S. boulardii5 billionYMOS90 capsules
Pure Encapsulations S. boulardii10 billionYN/A60 capsules
Seeking Health S. boulardii5 billionYN/A60 capsules

Jarrow Formulas S. Boulardii + MOS

Jarrow makes an S. boulardii product that contains 5 billion CFU of S. boulardii plus a strain of brewer’s yeast known as S. cerevisiae. The MOS in this product stands for “Mannan oligosaccharides,” which is derived from the Brewer’s yeast, and which offers pathogenic bacteria a binding site other than to the intestinal cells of the gut wall. This in turn allows the body to flush out these bad guys, rather than having them colonize the gut. (R) This is a very popular product, and some of the reviews on Amazon are effusive, with claims of curing chronic diarrhea and Crohn’s disease.

Pure Encapsulations S. Boulardii

If you want to avoid the Brewer’s yeast addition in the Jarrow formula, Pure Encapsulations makes a high-quality S. boulardii product that contains a mega dose of 10 billion CFU. Now, while Pure is known as a high-end brand, it is important to caution that not everyone will need or want this large of a dose, especially to begin. In his book Mold and Mycotoxins, Dr. Neil Nathan sets out a protocol for detoxing from mold and yeast overgrowth. He bases his protocols on mycotoxin lab work, specifically on which mycotoxin, if any, is elevated in his patient. He includes S. boulardii as part of the treatment for removing excess gliotoxin from the body (gliotoxin can be elevated where Candida overgrowth is present), but does say that he has seen patients have bad reactions to S. boulardii, especially initially, and that it is best to start slow, often with a half capsule, or even a quarter capsule.

If a doctor has diagnosed you with mold or yeast toxicity, this could be too large of a dose for you. This is a lyophilized preparation.

Seeking Health S. Boulardii

Seeking Health is a brand that is popular with a lot of naturopaths and holistic doctors. I list this formula here because it is lyophilized and at 5 billion CFU, contains a more conservative dose for those who may need to start slow with S. boulardii supplements.

S. boulardii survives the digestive tract to reach the colon and confer benefit

One of the knocks on some supplements is lack of bioavailability. For example, the bioavailability of curcumin has always been an issue. (R) Some say that if nutrients, like curcumin, could be delivered intact through the digestive tract, they could deliver a benefit, but our digestion destroys the nutrients before delivery. See also: Bioavailability of Lycopene.

This is not the case with S. boulardii.

To be effective, a probiotic must survive the gauntlet of the digestive system to arrive intact when it reaches the colon, which is why the World Health Organization defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host.” (R) In the case of lyophilized oral administration, as much as 3% of the living yeast of S. boulardii can be recovered in the fecal matter of recipients. This proves that S. boulardii survives the gastric acidity of our digestive tract. To quote this meta analysis of S. boulardii studies that appeared in the World Journal of Gastroenterology:

Organisms need to survive at body temperature (37°C), be resistant to stomach acids and bile acids, and exist in the competitive milieu of the intestinal tract. Probiotic strains of Saccharomyces have been shown to have these abilities. Although the optimal temperature for most strains of Saccharomyces range from 22-30°C, S. boulardii survives best at 37°C, giving it a unique advantage of being one of the few yeasts that do best at human body temperatures.

S. boulardii cannot be killed by antibiotics

As new research emerges about the importance of the health of our gut to our overall health, more and more people look for ways to guard against damage to their intestinal flora when they are forced to take a course of antibiotics. While it may still be worthwhile to take some bacteria based probiotics during a course of antibiotics, the antibiotics will kill the good with the bad, eliminating much of the value in a traditional probiotic. By contrast, S. boulardii is a yeast microbe, and as such, is immune to antibiotics. Antibiotics do not kill S. boulardii and S. boulardii can even be taken at the exact same time as a course of antibiotics. (R)

S. boulardii treats antibiotic associated diarrhea

As the name suggests, antibiotic associated diarrhea (AAD) is the problem of diarrhea as a side effect of taking antibiotics. AAD symptoms can range from mild to more severe (colitis) and can even result in death. (R) The problem is especially prevalent in hospital patients, but varies by the type of antibiotic.

AAD can be divided between late (diarrhea begins after antibiotic course ends) and early onset, with the timing of symptoms varying by the type of antibiotic. Early onset of AAD was associated with clindamycin, amoxicillin and ampicillin, while delayed-onset AAD was associated with erythromycin, ciprofloxacin and clarithromycin.

Clostridium difficile disease (CDD) is one of the most prevalent, and contagious, forms of AAD. CDD is nasty, and potentially fatal. (R) In fact, repeated CDD infections are sometimes treated with Fecal transplant procedures, including at world renowned hospitals like the Mayo Clinic. (R) Studies have shown that S. boulardii is the only effective probiotic in preventing CDD. Click here for the study.

CDD produces two exotoxins (toxin A and B) that suppress immune function. The extent to which patients have severe CDD symptoms is a function of the level of IgA and IgG antibodies they produce in reaction to those exotoxins. The greater the antibodies, the less severe their CDD symptoms.

Why is S. boulardii so effective at preventing CDD?

It seems to strengthen the immune system’s response to CDD. Studies in both rats and mice have shown S. boulardii to increase levels of immune system boosting IgA and IgG antibodies, which are the crucial metric in determining the severity of a bout of CDD. (R) (R) To quote one such study:

High titers of serum or intestinal antibodies against toxin A have been associated with asymptomatic carriage of toxigenic CDD and with shorter and less severe episodes of CDD.

S. boulardii helps prevent traveler’s diarrhea

In addition to its important role in preventing incidents of CDD, S. boulardii has been proven to help prevent the occurrence of traveler’s diarrhea. This is a big one for me when I’ve traveled to Asia. You want to jump right in and enjoy everything the locals do “Anthony Bourdain” style, but you also fear spending a large chunk of the trip in the bathroom.

This meta-analysis of studies found that probiotics, and especially S. boulardii, “significantly prevent traveler’s diarrhea.” 

S. boulardii and helicobacter pylori infection

Helicobacter pylori infection (H. pylori) is a stealth bacteria that is almost unbelievably common worldwide, with an estimated 50% of the world’s population infected. (R) (R) Although it can cause stomach ulcers and other symptoms, many people never know they have it.

H. pylori infection has been shown to increase the risk of gastric cancer by as much as 8 times. (R) From where I’m sitting, it’s amazing that H. pylori isn’t on more people’s radars. I was surprised to learn that in addition to its link to stomach cancer, it’s contagious, huge percentages of undeveloped countries carry the bug (as high as 80% in rural India), and it can cause an increase in LDL. (R) (R) (R)

I’d heard very little about H. pylori until I started researching S. boulardii, and learned that S. boulardii can help mitigate some damage caused by H. pylori, especially AAD caused by the standard antibiotic treatment regimen.

Patients receiving antibiotics to treat H. pylori infection had significantly lower incidents of AAD when taking S. boulardii. (R)

Interestingly, this study hinted at the possibility that S. boulardii may “induce morphologic changes in H. pylori cells consistent with cellular damage.” Further research is needed to determine whether S. boulardii can in fact kill, or alter, H. pylori.

See our top choices of s. boulardii supplements.

S. boulardii and treatment of chronic diseases

Crohn’s disease

S. boulardii was shown to help Crohn’s disease patients stay in remission, as well as improve intestinal permeability. (R)

Irritable bowel syndrome

S. boulardii supplementation improved quality of life for IBS patients, but not bowel frequency or stool consistency. (R)

This meta-analysis found that, when compared with placebo, probiotics improved global IBS symptoms as well as reduced abdominal pain in IBS patients. (R)

S. boulardii in healthy people

In those struggling with AAD, we know that S. boulardii plays an important role in bolstering the immune system against exotoxins. What is the mechanism for action in healthy people?

This study essentially found that intestinal inflammation makes it easier for S. boulardii to do its work, since the breakdown in the intestinal lining helps it reach immune cells. However, in a healthy intestine, the mechanism of action is likely not immune-mediated. Instead, it looks like S. boulardii helps in maintaining a healthy bacterial state in the gut (i.e. S. boulardii acts as a microbiome fertilizer allowing healthy bacteria to flourish and crowding out more damaging strains), and by strengthening epithelial integrity, basically keeping the gut lining strong and preventing leaky gut. (R)

Saccharomyces boulardii and your genes

Above I’ve discussed a wide range of health improvements linked with S. boulardii. Yet an important question remains about the potential genetic contributions to the various disorders mentioned above.

Understanding digestive health and its interaction with allergies is a highly complex area, and so it can be difficult to identify genes which might play a role. However, in the more serious disorders such as Crohn’s disease, there are a few genes of interest that keep appearing.

NOD2

NOD2, or Nucleotide-binding oligomerization domain-containing protein 2 to give it its full name has a strong association with Crohn’s and IBD. So strong in fact that when it was first discovered it was named IBD1, or inflammatory bowel disease protein 1. NOD2 is a receptor protein which is expressed in the lining of the gut, it recognizes bacterial molecules and stimulates an immune response.

Two SNPs within NOD2 have been described which display a strong association with the development of Crohn’s. rs2066844 or C2023T which describes a change from a ‘C’ allele to a ‘T’ allele in approximately 2% of the population. Secondly, rs2066845 or G722C which describes a change from a ‘G’ to a ‘C’ allele in less than 1% of the population (R, R). Both of these SNPs induce a change in the protein structure of NOD2, which leads to an increased susceptibility to developing Crohn’s disease, although the authors of the report do not confirm a methodology.

It is however possible to hypothesize that NOD2 produced by the risk ‘T’ allele of rs2066844 C2023T, or the risk ‘C’ allele of rs2066845 G722C is either more sensitive to bacteria, or is present in greater amounts, meaning that it more easily stimulates an immune response.

IL23R

The second gene of interest is interleukin 23 receptor or IL23R. As its name suggests IL23R is the receptor protein for IL-23. IL-23 is a molecule which is released by immune cells when they detect a bacterial pathogen, which acts to stimulate the recruitment of other immune cells and generates an immune response. So it’s fairly easy to see how this could play a role in the development of Crohn’s disease.

Sure enough, there are two SNPs both of which are associated with an increased risk of developing Crohn’s. rs1004819 or G653-2380A which leads to the change of a ‘G‘ allele to an ‘A’ allele in approximately %40 of people. And also rs2201841 or A956-8194G which leads to the change of an ‘A’ allele into a ‘G‘ allele also in about 40% of the population.

As above the mechanism by which these two SNPs increase the risk of developing Crohn’s is poorly understood, however there is a significant association between them (R). It is possible that a similar effect as was hypothesized for NOD2 is occuring, where a more sensitive form of IL23R is produced by those carrying the risk ‘G‘ allele of either rs1004819 G653-2380A or rs2201841 A956-8194G. This more sensitive IL23R may then induce an immune response and inflammation much more readily than the normal form.

Tying it back to S. boulardii 

There are have been no studies directly looking at S. boulardii in relation to these, or any other SNPs, although a beneficial effect for Crohn’s in general has been described (R). However, it is easy to see how the beneficial effects described above would be helpful for those at risk of developing Crohn’s. By promoting a healthy gut flora S. boulardii may reduce the chance of the sensitive NOD2 or IL23R proteins, in those carrying the risk allele, being stimulated thus preventing the generation of an immune response.

Bottom line

The bottom line with S. boulardii is that it’s a proven supplement that has been shown the greatest efficacy in helping people with compromised gut health crowd out the “bad guys” so the “good guys” have a chance to flourish once again.

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25 Comments

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  1. Angie says:

    Please please help me, Ive been bedridden since 2014. Long story why…I have Lyme and co-infections. I was recently diagnosed with pneumonia I have had C. diff in the past. But now, to make matters worse, I was put on steroids in 2008 before I knew I had Lyme.

    When I had C. diff, I wasn’t on steroids, which as you know are immunosuppressants. My question for you is you said only good s. boulardii doesn’t need to be kept in the fridge. I have diarrhea now and can barely eat. I’m afraid I’m going to die. What s. boulardii brand doesn’t need kept in the refrigerator? That’s my main question. Please, I beg you please help me. If I catch it again I will die for sure. I have a son who is 12. I don’t want to leave him so I beg you what s. boulardii brand do you use. Every brand I have ever had ordered for me says to refrigerate. Thank you for your time.

    • Angie, I am so sorry to hear you’ve been suffering. To begin, these are all questions for your doctor, not for us, however, I can tell you that the best S. boulardii preparations are usually lypholized, meaning they’re freeze dried, and yes, do not need to be refrigerated. Thorne makes an excellent product and the Spartan Strain product on our site is top notch as well. I wish you good luck.

    • Chris says:

      I have c diff for 3 months, thought I might die as well. I am strong, healthy 33 male. Terrible Ilness. The antibiotic Vancomycin is the only thing to help me so far. Take this antibiotic, when your finished start taking probiotics. Call me if you want 1 403 463 6877.

  2. Terri says:

    Angie,
    So sorry to hear of your suffering- sadly, too many people have been in or are in similar ways. My experience became better by researching and education, finding awareness and learning to ask the right questions.
    Maybe try researching “The Infection Connection” with Dr. Nikolas Hedberg of N.C.
    Hedberg also has extensive research on healing Lyme disease, and it is in layman terms. He can also be found thru Hawthorne University webinars- Simpy search Dr. Nikolas Hedberg Hawthorne University-
    “The Infection Connection” “Lyme Disease” “Auto Immune Disease and Infection”.
    Dr. A. Vojandi has a great webinar on infections and autoimmune disease, much more technical.
    Barbara O’Neill of Misty Mountain Re-Treats of Australia has some great educational videos on how our bodies work and how to help us be healthy. Very easy to listen to and learn.

    Of course this is just information for you to research and learn by. Always be sure to follow the advise of your doctor.
    Hopefully, this information is useful to you in some way.
    God Bless you with a speedy recovery.

  3. Judy says:

    Is there a child’s chewable or a capsule that could be put into applesauce for one who won’t swallow pills that you would recommend?

      • Nelly says:

        Judy, my daughter is now taking S. Boulardii. Our naturopathic doctor prescribed the capsules and I break it open and pour it in her juice – she never noticed that she has been taking it.It is Saccharomyces Boulardii 100 caps by Kirkman Labs. I hope this helps.

  4. Carol says:

    I bought this type of probiotic because my son had diarrhea…I was wondering if I take it and I don’t have diarrhea would it constipate me?

    • Cynthia says:

      Hi Carol,

      I take have taken Florastor and also Jarrow Formulas that contain saccharomyces boulardii lyophilized and have not experienced any issues with constipation. I have yet to try the Spartan Strain by Gene Foods but hope to at some point.
      I hope this helps! 🙂

  5. Kate Becker says:

    Hi there! Thanks for all the wonderful information! It this a good option to take to avoid yeast infections after a course of cipro? All the other benefits sound wonderful too!

    Thanks again,
    Kate

  6. susie says:

    Hi, IBS-c sufferer here along with chronic yeast infections, arthritis, fibromyalgia.

    You mentioned something about alternating one week on and one week off of SB. Can I stay on it consistently for awhile to help with the candida overgrowth and my other problems?

    Thanks,
    Susie

  7. Tami says:

    How do you know if body reactions are side effects that are signs the yeast is doing its job or if they signal that one should stop taking them?

    After a week, my throat is sore, my tongue burns and is coated, my eyes feel red and scratchy, my ears ringi, my belly fills with gas and bloats and I’m still having soft stool and diarrhea.

    I started after a three-week vancomycin IV treatment for a MRSA infection. I have bad reactions to probiotics and read that could be because the glycocal mucous layer is damaged and s boulardi can repair it and crowd out Candida too.

    Prior to my vancomycin treatment, my integrative doctor had started me on a anti-candida supplement , but recommended I stop for a bit and take probiotics to rebuild after the antibiotic. Even on very small doses of probiotics, I am miserable with bloating and abdominal pain.

    Are these side effects normal and how long can they last?

    • Tami, these are questions best left for your doctor, but I can tell you this: Dr. Neil Nathan, a physician and mold expert in California, recommends stopping with any supplement that makes symptoms worse. His protocols are geared towards Candida and mycotoxins, but if something is making you sick, it’s likely a good idea to stop, or at a minimum, cut way way back on dosing. There is nothing wrong with taking 1/4 of a capsule, supplement doses are often arbitrary.

  8. Ann says:

    I’ve recently been given a bottle of pro bio five advantage by plexus have you ever heard good or bad about this product.

    • doreen scobie says:

      I’m taking the probio5 plexus supplement for candida overgrowth and bad bacteria in my intestines. It’s a premium product so stick with it. I have been on it for a month and feeling better. I also take the plexus vitalbiome, biocleanse, and the pink drink.

  9. Jerry says:

    Since the Jarrow brand has MOS will it still help strengthen the gut or just pass through. Thanks for being here!

  10. Liz says:

    I have been taking Sacc B for 2 and a half months to support my anti inflammatory diet. My doctor recommended that you switch probiotic strains every 3 months so your body does not grow used to it. Can you recommend how exactly to use probiotics? Do I just switch them every 2 weeks? Just as support to the anti inflammatory diet. thanks.

  11. doreen scobie says:

    I’m taking the probio5 plexus supplement for candida overgrowth and bad bacteria in my intestines. It’s a premium product so stick with it. I have been on it for a month and feeling better. I also take the plexus vitalbiome, biocleanse, and the pink drink.

  12. Eric says:

    Hi John-

    I had a question for you. I’ve read some reports saying that yeast and s bouldardii is high in histamine. If you have histamine intolerance, wouldn’t this make it worse? Did you have any increase in histamine issues while you took this supplement? Thank you

    • Hey Eric, it depends on what is causing the mast cell activation. It is true that some clinicians list S. Boulardii as contraindicated for people with histamine issues, however, clinicians like Dr. Neil Nathan in California suggest S. Boulardii when mold and yeast is to blame for the over active immune response. I believe Dr. Nathan would use gliotixin labs as part of a mycotoxin panel as one of the indicators.

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