Natural support for gut health from a probiotic yeast
Probiotics are “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.”[1] You may be familiar with probiotic supplements that contain lactobacilli and/or bifidobacteria, which are families of beneficial bacteria.[2] However, there is also a yeast species that qualifies as a probiotic: Saccharomyces boulardii, pronounced “SAK-a roe-MYE-sees boo-LAR-dee-eye.”[3],[4] S. boulardii is related to common baker’s and brewer’s yeast (S. cerevisiae), but there are key differences that allow the former to benefit gut health.[5],[6],[7]
S. boulardii has an interesting history dating back to the last century. The yeast was discovered and named after scientist Henri Boulard who was doing research in Indochina in the 1920s. During a cholera outbreak, Boulard noticed that some people chewing the skin of lychee and mangosteen, or preparing teas from these tropical fruits, did not develop cholera symptoms.[3] He isolated a yeast strain, later named S. boulardii, which was responsible for the effects. The strains of S. boulardii used in probiotic supplementation today are closely related to Boulard’s strain.[8]
The properties and benefits of S. boulardii have been reported in more than 600 peer-reviewed articles and over 90 clinical trials.
S. boulardii achieves peak concentrations in the intestine within 3 to 4 days, and maintains a high stable level as long as the yeast is taken daily in adequate amounts.[5],[9] The properties and benefits of S. boulardii have been reported in more than 600 peer-reviewed articles and over 90 clinical trials, which are highlighted here:
- Supports a healthy microbiome: S. boulardii creates a favorable growth environment for the beneficial intestinal microbiota.[10],[11] It accelerates the recovery of the microbiota after antibiotics,[12],[13],[14] and increases the numbers of bacteria that produce butyrate,[15],[16] a short-chain fatty acid that reduces inflammation.[17]
- Protects intestinal cells from damage: S. boulardii interacts with the intestinal mucosa to preserve the integrity of the epithelial cell layer, enhance wound repair, and reduce leaky gut.[18],[19],[20],[21],[22]
- Improves digestion: S. boulardii increases the intestinal activity of digestive enzymes, including sucrase, maltase, and lactase, which may benefit people with digestive issues.[23],[24] This increase in enzyme activity may improve the absorption of carbohydrates which have been associated with irritable bowel syndrome (IBS) and diarrhea.[25]
- Releases nutrients: S. boulardii releases 1,500 different substances, including amino acids, nucleic acids, polyamines, antioxidants, flavonoids, B vitamins, minerals, and prebiotics such as beta-glucan, which enhance nutrition of the host and of the microbiota.[3],[22],[24],[26]
- Inhibits pathogens: Supplementation with S. boulardii helps protect against gut pathogens, including Clostridum difficile (C. difficile), and reduces the risk of diarrhea from many causes, as discussed below.
Anti-microbial effects of S. boulardii
International guidelines recommend the use of S. boulardii for children with gastroenteritis caused by rotavirus infection.[27],[28],[29] Supplementation with S. boulardii helps restore the normal microbiota, an effect that is correlated with a reduction in diarrhea.[30]
S. boulardii supplementation also reduces the risk of diarrhea from gastrointestinal infections, antibiotic use, and IBS.[31],[32],[33] In one study of individuals with IBS and diarrhea, supplementation with S. boulardii (200 mg three times daily) significantly improved IBS symptoms after one month.[34]
The probiotic activity of S. boulardii is especially relevant for antibiotic-associated diarrhea (AAD) and C. difficile infections.[35] Diarrhea is a common side effect of antibiotic administration,[36] and the use of S. boulardii can significantly reduce the incidence, duration and/or severity of AAD.[14],[37],[38],[39] S. boulardii reduces this risk in part by protecting and restoring levels of healthy gut microbes.[10],[37] Since S. boulardii is affected only by antifungal medications and not by antibiotics, it has a big advantage over bacterial probiotics for this indication. [40]
Since S. boulardii is affected only by antifungal medications and not by antibiotics, it has a big advantage over bacterial probiotics for this indication.
C. difficile, a pathogenic bacterium that causes colitis, is actually responsible for up to 25% of AAD cases.[41],[42] Studies show that C. difficile normally exists at very low levels in the healthy colon, but it can flourish when antibiotics destroy large numbers of protective gut microbes.[43] The destruction of indigenous bacteria that metabolize bile acids causes an accumulation of cholic acid, a primary bile acid, which triggers the growth of C. difficile in the intestine.[44],[45] Then, once C. difficile takes hold, it carries out a form of chemical warfare by inducing other gut microbes to produce indole, a substance that limits the growth of beneficial bacteria and hampers microbiota recovery.[46]
S. boulardii has its own, equally clever means of combating C. difficile.
Fortunately, S. boulardii has its own, equally clever means of combating C. difficile. It prevents the accumulation of cholic acid, which puts the brakes on C. difficile growth.[44] In this respect the action of S. boulardii is similar to that of fecal microbiota transplantation (a more extreme approach that replaces the entire microbiota with that of a healthy individual) which also may exert its effects by modulating colonic bile acid composition.[47]
By these and other mechanisms, S. boulardii also can help prevent the recurrence of C. difficile infection. In one study, when S. boulardii was taken daily for one month (1 gram per day) along with high-dose vancomycin, a significant decrease in recurrences was observed in patients, with only 16.7% having a recurrence versus 50% in those only taking the vancomycin.[14]
S. boulardii also may be helpful for individuals with Helicobacter pylori infection, which is typically treated with two different antibiotics and a proton pump inhibitor.[48],[49],[50] This drug combination is a double whammy, because both antibiotics and proton pump inhibitors increase the risk of diarrhea and C. difficile.[51] Thankfully, the administration of probiotics can reduce the side effects of H. pylori treatment, and may even increase the overall efficacy.[2] A recent clinical trial showed that S. boulardii, taken in tandem with the indicated pharmaceutical treatments for H. pylori, reduced the incidence of diarrhea from 46% in the control group to only 2% in the S. boulardii group.[50]
In laboratory studies, S. boulardii was shown to antagonize Salmonella, Escherichia coli (E. coli), Listeria, and Staphylococcus aureus, suggesting a broad range of activity against these additional gastrointestinal pathogens.[52],[53],[54],[55] S. boulardii also was shown to inhibit the growth of Candida spp., the most common cause of human fungal infections.[56],[57],[58] Researchers discovered that S. boulardii secretes capric acid, a medium-chain fatty acid that strongly inhibits C. albicans.[59]
Finally, animal and human studies suggest that supplemental S. boulardii may be useful in treatment of Giardia lamblia, a parasite that lives in contaminated water and causes the diarrheal illness known as giardiasis.[60],[61] In the United States, G. lamblia is the most common intestinal parasitic disease affecting humans.[62]
Summary
If Henri Boulard were alive today, he might be surprised to find that his 1920 discovery of a yeast strain from lychee fruit has led to one of the most successful probiotic species of all time. The multiple mechanisms of action of S. boulardii may explain its beneficial effects in a variety of gastrointestinal conditions. Collectively, the research shows that S. boulardii may be a good choice to protect and restore a healthy gut microbiota as it shields the gut against the damaging effects of antibiotics and reduces pathogen virulence as well.
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