Is S. boulardii Good for SIBO? What the Evidence Says

Why You May Want This Probiotic Yeast in Your SIBO Treatment Protocol

• SIBO 101|
• S. boulardii for SIBO|
• Using Probiotics for SIBO|
• S. boulardii SIBO Treatment Protocol|
• S. boulardii is Good for SIBO|

There’s a trend in integrative and functional medicine to shy away from using probiotics, like S. boulardii, for the treatment of SIBO (Small Intestinal Bacterial Overgrowth). I mean, it kind of makes sense in theory – why would you add more bacteria or yeast (in the case of S. boulardii) to an environment that’s overrun with microbes? While this type of mechanistic thinking may seem logical, the current research just doesn’t support it. 

The truth is that while we don’t yet have a lot of evidence to say definitively that S. boulardii on its own improves SIBO, the evidence we do have (and the probiotic evidence overall) suggests that S. boulardii and other probiotics are beneficial, and can safely be included in a SIBO eradication protocol.

In this article, I’ll share what the research says about using S. boulardii and other probiotics for SIBO, and I’ll get into why some providers may still recommend avoiding probiotics during treatment. 

I’ll also provide you with an evidenced-based S. boulardii SIBO protocol that you may want to trial if you’re suffering from symptoms like gas, bloating, constipation, and abdominal pain. Let’s start off with a little background on SIBO and a review of how S. boulardii may help.

SIBO 101

Before getting into how S. boulardii may improve small intestinal bacterial overgrowth (SIBO), it’s important to get clear on what SIBO is. It’s not actually a “condition” per se, but rather a lab finding that may indicate general dysbiosis (an imbalance of microbes) in the small intestine. We normally “diagnose” it based on a glucose or lactulose breath test, but a positive SIBO test doesn’t necessarily mean you’re unwell, or that you need to change anything.

SIBO, which often co-occurs with irritable bowel syndrome (IBS), can create gas, bloating, abdominal pain, constipation, and diarrhea [1, 2, 3, 4]. If you’ve got these symptoms, several research-backed therapies can help to rebalance your gut microbiome (i.e. get rid of SIBO). These include probiotics [5], diet-related changes [6], fasting [7], digestive support [8], and herbal antimicrobials [9]. 

It will likely take a combination of these therapies to improve your gut health for the long run, but many providers leave probiotics (like S. boulardii) off the table when it comes to treating SIBO, even despite high-quality evidence that probiotics are extremely helpful.

Now that you have some background on SIBO, let’s take a look at Saccharomyces boulardii, or S. boulardii, a yeast with probiotic-type actions in the human gut, and why it may be an excellent option for SIBO.

How Does S. Boulardii Improve SIBO?

We don’t have much research on the effects of S. boulardii for treating SIBO, but the studies we do have suggest it may eradicate SIBO better than antibiotic or placebo treatment, and it may also improve SIBO-related symptoms [10, 11, 12]. S. boulardii may improve SIBO outcomes via four key mechanisms:

• Reducing bacterial overgrowth [10, 11]
• Reducing digestive symptoms [13, 14, 15]
• Restoring the gut microbiome [12, 16]
• Reducing inflammation [17]

Let’s dig into each of these and the corresponding research.

S. boulardii and Bacterial Overgrowth

Bacterial overgrowth is what we’re trying to combat in people with SIBO. A couple of small randomized clinical trials looking at how well S. boulardii could eradicate bacterial overgrowth in people with SIBO found promising results. The first showed patients with systemic sclerosis and SIBO who were given S. boulardii or S. boulardii plus an antibiotic had higher eradication rates and improved GI outcomes when compared to those who only received antibiotic treatment [10]. 

Another small study of people with cirrhosis and SIBO found S. boulardii significantly eradicated the SIBO and also reduced abdominal fluid buildup [11].

Overall, S. boulardii may reduce bacterial overgrowths by [10]:

• Inactivating the toxins made by bacteria
• Helping gut cells mature
• Freeing up enzymes that are good for S. boulardii and your gut
• Inhibiting inflammation
• Regulating the gut immune system 

S. boulardii and Digestive Symptoms

People with SIBO often have painful, sometimes embarrassing digestive symptoms, like bloating, gas, altered stool consistency, and abdominal pain, which S. boulardii may help to soothe. While the research here isn’t necessarily on SIBO specifically, several meta-analyses have found S. boulardii to improve digestive symptoms in a variety of situations. 

For example, in kids with acute gastroenteritis, treatment with S. boulardii improved diarrhea and decreased the length of hospital stay [13]. It also reduced the risk of antibiotic-associated diarrhea in both kids and adults, and reduced the risk of Clostridium difficile-related diarrhea by 75% in kids [14]. 

Another meta-analysis found a yeast similar to S. boulardii, Saccharomyces cerevisiae, to significantly improve abdominal pain and discomfort, bloating, and stool consistency in IBS patients [15, 18]. 

Overall, S. boulardii may improve a variety of digestive symptoms by:

• Preventing pathogens from setting up camp in the gut wall, which makes them susceptible to peristalsis and excretion in bowel movements [13, 14]
• Competing for resources [14]
• Promoting a healthy balance of microorganisms [13]
• Inactivating the toxins made by bacteria [13, 14]
• Reducing excessive fluid buildup in the intestines [13]
• Regulating the gut immune system and immune response [13]
• Inhibiting inflammation [14]
• Numbing pain [15]

S. boulardii and the Gut Microbiome

Antibiotic therapy can disrupt the gut microbiome and shift it toward dysbiosis [16]. This is obviously something we want to avoid since gut dysbiosis can create a negative cascade of events leading to leaky gut, inflammation, and altered immune system function.  

A randomized clinical trial found healthy people who took S. boulardii experienced little change in their gut flora balance whereas those taking antibiotics alone had a shift in their microbiota toward dysbiosis [16]. An exciting feature of this study was that S. boulardii added to antibiotic therapy reduced the detrimental effects of antibiotics [16]. 

And other studies have highlighted the fact that since S. boulardii  is a yeast, it’s resistant to antibiotic treatment, so it’s effective even when taken with antibiotics [10]. This is excellent news since antibiotic therapy is sometimes necessary, and we have good evidence here that this probiotic yeast may combat the negative gut microbiome side effects.

In another clinical study in people with SIBO and IBS-D (diarrheal type IBS), those who took S. boulardii and were educated on how to follow a low FODMAP diet for two weeks had improved SIBO, abdominal pain, and diarrhea. 

Unfortunately, this study didn’t compare S. boulardii to a placebo group, so we can’t say for sure the improvements were related to it alone [12]. But in participants who improved while taking S. boulardii, the levels of Proteobacteria, which is associated with dysbiosis, were reduced. In addition, the levels of F. prausnitzii, which has anti-inflammatory effects and is associated with better health, increased. So, it’s possible that the S. boulardii helped to shift the gut microbiome profile to a more favorable one [12].

Overall, S. boulardii may improve gut microbiome balance by: 

• Inactivating toxins made by bacteria [16]
• Preventing pathogens from setting up camp in the gut wall, which makes it easier for you to excrete them in bowel movements [16]
• Regulating the gut immune system [16]
• Promoting a healthy balance of microorganisms [12]

S. boulardii and Inflammation

Dysbiosis can create inflammation in the GI tract. One randomized controlled trial of people with IBS-D who were taking ispaghula husk (an anti-inflammatory prebiotic) either took a placebo or added S. boulardii. The S. boulardii group had significant reductions in inflammatory markers like IL-8 and TNF-alpha, increases in anti-inflammatory markers, and improved quality of life when compared to those not taking it [17].

Overall, S. boulardii may reduce inflammation by [17]:

• Making dendritic cells (cells that influence the immune system) less reactive to bacterial toxins such as lipopolysaccharide.
• Preventing pathogens from setting up camp in the gut wall, which makes it easier for you to excrete them in bowel movements.

Despite these positive research findings, many providers still wait to add probiotics until after SIBO has been treated. But the research clearly doesn’t support this way of thinking. So let’s discuss why it’s better to go ahead and use probiotics like S. boulardii for SIBO treatment, and why some providers are resistant to update their recommendations.

Using Probiotics for SIBO

I’m passionate about using the best evidence we have to make informed decisions about treating gut conditions. But many integrative providers put probiotics on the back burner when it comes to SIBO, which is extremely infuriating because we have high-quality evidence that probiotics are very effective for improving it. 

Providing inaccurate information like this is a disservice to the patient and other well-intentioned healthcare providers. So, I want to make it clear here that probiotics, including S. boulardii, should absolutely be trialed for people with SIBO, and here’s why:

Research suggests that while probiotics may not be helpful for preventing SIBO, they do appear to be able to eradicate it, and the gastrointestinal symptoms it causes [5, 19]. 

One meta-analysis of 22 clinical trials found SIBO patients who took probiotics were significantly more likely to clear SIBO and have lower hydrogen levels and less abdominal pain when compared to patients with SIBO who didn’t take probiotics [5]. 

In addition, an observational study found IBS patients with SIBO who took probiotic strains that included Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus plantarum, and S. boulardii, had a significant drop in their IBS symptom scores and higher satisfaction with bowel function [19]. 

While we don’t know the exact mechanisms, probiotics may be able to combat pathogens and thus bacterial overgrowths by [20]:

• Strengthening the intestinal wall
• Making the gut wall more hospitable to probiotic bacteria
• Preventing pathogens from sticking to the gut wall
• Occupying space pathogens might otherwise use to multiply
• Making substances that can kill or inhibit pathogens
• Priming the immune system to attack pathogens 

At this point, you may be wondering why, with the good quality evidence we have, some providers are still against the use of probiotics for SIBO. I think part of the issue may be the misinterpretation of poor-quality research and research bias. Here are some examples:

Naysayers of probiotic use in SIBO often quote an observational study that concluded that probiotics seemed to aggravate SIBO [21]. However, this study was poorly designed and has been discredited for the authors’ inaccurate interpretation. 

Others have misinterpreted a different observational study that merely found that a small subset of healthy people who took probiotics had higher methane levels afterward. The authors concluded that this potential for higher methane levels as a result of probiotics could skew breath test results, and that it might be good to stop probiotics before taking a breath test. They did NOT use their results to speculate that probiotics could be causing methane SIBO, as some people may believe [22].

So, now that you know that S. boulardii and other probiotics are a safe and effective option for treating SIBO, let’s discuss an evidence-based protocol.

S. boulardii Treatment Protocol for SIBO

While there aren’t many trials using S. boulardii specifically for SIBO, we can look at the research using this probiotic yeast in the treatment of IBS, which often co-occurs with SIBO [1, 2, 3, 4].  We can speculate from the vast amount of IBS research we have that part of why S. boulardii and its cousin, S. cerevisiae, have improved digestive symptoms and inflammation in IBS patients may be their ability to get rid of SIBO [15, 17]. Since S. boulardii is safe and likely effective, it’s worth it to trial it if you have SIBO.

In one meta-analysis that included three trials using S. boulardii for IBS, the most common effective dose was 10–15 billion CFU per day for 4–6 weeks [23].  In another meta-analysis of 29 clinical trials of S. boulardii for acute gastroenteritis in kids, the most common dose was 10 billion CFU, or 500 milligrams per day [13]. So we can assume that a dose in this range will likely be effective for SIBO.

You may hear that you need to take a probiotic like S. boulardii at a certain time of day or with or without food. But the research indicates that S. boulardii is resistant to stomach acid, so you can take it at whatever time is most convenient for you [24].

With these things in mind, here’s a chart detailing an evidence-based S. boulardii protocol for SIBO [13, 23, 24]:

S. boulardii is Good for SIBO

Is S. boulardii good for SIBO? Yes, it is, although some leading experts continue to recommend the avoidance of probiotics like S. boulardii for SIBO. High-quality research, in the form of meta-analyses, clearly demonstrates that probiotics are safe and effective for SIBO, and this has also been my experience in the clinic. 

While the research on S. boulardii for SIBO is limited, this probiotic yeast may impart its benefits specifically by reducing bacterial overgrowths, improving digestive symptoms, rebalancing the gut microbiome, and reducing inflammation. 

In these cases, where research is still in its infancy, I go back to my motto of being evidence-based, not evidence-limited. The studies we do have suggest that S. boulardii may actually eradicate SIBO better than antibiotics, and it may also improve SIBO-related symptoms. The studies often cited by naysayers of probiotics for SIBO are either poorly done, or misinterpreted. And I don’t want you to miss out on a very beneficial treatment option because of the advice of experts who have an inaccurate interpretation of the evidence. 

If you’re experiencing the symptoms of SIBO, your most helpful option for improving your digestive health is a comprehensive gut-healing approach, which you can find in Healthy Gut, Healthy You. Probiotic supplements that include S. boulardii are a part of my step-by-step plan, and research suggests it’s probably best to use at least 10-15 billion CFU daily for 2-3 months. If you’re not a do-it-yourselfer, you can always contact us at the Ruscio Institute for Functional Health for a personalized plan.

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.