Saccharomyces boulardii (S. boulardii) is a type of probiotic ("friendly" organism). It's a yeast that is actually a strain of Saccharomyces cerevisiae.
"Friendly" organisms such as S. boulardii can help fight off "bad" organisms that might cause diseases. S. boulardii is different from other strains of S. cerevisiae, commonly known as brewer's yeast and baker's yeast.
People commonly use S. boulardii for treating and preventing diarrhea, including rotaviral diarrhea in children. It's also used for other types of diarrhea, acne, a digestive tract infection that can lead to ulcers, and many other conditions, but there is no good scientific evidence to support many of its other uses. There is also no good evidence to support using S. boulardii for COVID-19.
Don't confuse S. boulardii with other probiotics, or with fermented food products such as fermented milk, kefir, or yogurt. These are not the same.
Is It Effective?
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
- Diarrhea. Taking S. boulardii by mouth can reduce how long diarrhea lasts in children. It's not clear if it helps children with longer-lasting diarrhea or if it helps adults.
- Diarrhea in people taking antibiotics (antibiotic-associated diarrhea). Taking S. boulardii by mouth can help prevent diarrhea in adults and children being treated with antibiotics.
- Infection of the gastrointestinal tract by bacteria called Clostridioides difficile. Taking S. boulardii by mouth seems to help prevent diarrhea from C. difficile infection. Taking it along with antibiotics also seems to help prevent this infection from coming back.
- A digestive tract infection that can lead to ulcers (Helicobacter pylori or H. pylori). Taking S. boulardii by mouth along with standard H. pylori treatment helps prevent side effects such as diarrhea and nausea that occur with standard H. pylori treatment. But it isn't clear if taking S. boulardii helps these standard treatments to work better.
- A serious intestinal disease in premature infants (necrotizing enterocolitis or NEC). Most research shows that giving S. boulardii by mouth to preterm infants prevents NEC.
- Diarrhea caused by rotavirus. Taking S. boulardii by mouth seems to reduce how long diarrhea lasts in children with diarrhea caused by rotavirus.
- Travelers' diarrhea. Taking S. boulardii by mouth seems to reduce the risk of developing diarrhea while traveling.
- Blood infection (sepsis). Giving S. boulardii to preterm infants by mouth does not prevent sepsis.
There is interest in using S. boulardii for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Is it Safe?
When taken by mouth: S. boulardii is likely safe when used for up to 15 months. It can cause gas in some people.
Special Precautions & Warnings:
Pregnancy and breast-feeding: There isn't enough reliable information to know if S. boulardii is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.
Children: S. boulardii is possibly safe for children when taken by mouth appropriately. But diarrhea in children should be evaluated by a healthcare professional before using S. boulardii.
Elderly: Older adults might have an increased risk of fungal infection when taking S. boulardii. Stay on the safe side and avoid use.
Digestive tract disease: S. boulardii has caused fungal infections in people with diseases of the digestive tract. If you have a digestive tract disease, talk with your healthcare provider before taking S. boulardii.
Weakened immune system: S. boulardii has caused fungal infections in people with weakened immune systems. In many cases, the infection was due to a catheter becoming contaminated. If you have a weakened immune system, talk with your healthcare provider before taking S. boulardii.
Yeast allergy: People with yeast allergy can be allergic to products containing S. boulardii. Stay on the safe side and avoid these products.
Medications for fungal infections (Antifungals)
Interaction Rating=Minor Be watchful with this combination.
S. boulardii is a fungus. Medications for fungal infections help reduce fungus in and on the body. Taking S. boulardii with medications for fungal infections can reduce the effects of S. boulardii.
There are no known interactions with herbs and supplements.
There are no known interactions with foods.
In adults, S. boulardii has most often been taken by mouth in doses of 500-1000 mg (about 10-20 billion colony-forming units) daily for 4 weeks. In children, S. boulardii has most often been taken by mouth in doses of 250-500 mg (about 5-10 billion colony-forming units) for up to 4 weeks. Speak with a healthcare provider to find out what dose might be best for a specific condition.
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