Saccharomyces boulardii (S. boulardii or S.B. for short, and pronounced Sack-a-row-my-sees boo-lar-dee), is a microorganism which differs greatly from the well-known probiotic species such as acidophilus. Saccharomyces boulardii is actually a natural yeast, originally extracted from the lychee fruit.

This microorganism is understood to be a transient; meaning that it passes through the system without binding to the gut wall lining (a sought-after feature in high quality probiotic bacteria). S. boulardii however has undergone years of rigorous clinical research demonstrating not only its safety, but its ability to support digestive health.

OptiBac Probiotics is the only UK company to do a pure Saccharomyces boulardii supplement (which contains 5 billion pure micro-organisms per capsule) and can be found here.

Saccharomyces boulardii can also be found in our supplement For travelling abroad ( which contains 1 billion micro organisms per capsule, combined with other live cultures.)

Microscopic image of S. boulardii microorganisms.

In terms of cost per billion microorganisms, Saccharomyces boulardii by OptiBac Probiotics is the best value supplement containing S. boulardii currently available in the UK. To read more about S. boulardii from OptiBac Probiotics, so that you can recommend it with confidence, click here.

The name

Saccharomyces boulardii lends its name to the French scientist, Henri Boulard, who discovered the probiotic yeast in 1923 in South East Asia where he noticed people using the skin of lychee fruit for its beneficial health properties. S. boulardii is often referred to as S. boulardii lyo, where the 'lyo' is short for 'lyophilisation' - a form of freeze-drying which S. boulardii normally undergoes in its supplement form. This process allows the supplement to be shelf-stable so that refrigeration is not necessary. OptiBac Probiotics Saccharomyces boulardii is lyophilised.

For more information on the classification of Saccharomyces boulardii, please read our in-depth article.


  • Hello,

    I know probiotics are suitable in pregnancy, I am wondering in particular about the Saccharomyces Boulardii strain, is this particular strain suitable in pregnancy?

    I would appreciate a reply as soon as you can.

    Thank you


    P.S. I am a huge fan of your probiotics.

  • Hi Sinead

    Thanks for your question about Saccharomyces boulardii, and for your great feedback! So glad that you've found a benefit from using our products.

    Actually, as a company we've decided not to recommend Saccharomyces boulardii for pregnant and nursing mothers. This recommendation is given primarily based on the lack of related research on its use in pregnancy, rather than because safety issues have been identified. So while there is no evidence to suggest that Saccharomyces boulardii is harmful when used during pregnancy or while breastfeeding, there is also no strong evidence to prove that it is completely safe to use.

    We also know that it is a probiotic yeast, so has a different genetic make up and different modes of actions to probiotic bacteria which have been tested widely in pregnancy. Therefore, although it is one of the most well-researched probiotics in the world and used routinely in hospitals throughout Europe, we simply wish to err on the side of caution and not recommend it to pregnant women, until we see further research in the area.

    As a company, the strength of our range lies in the huge number of clinical trials that support the use of our products (160 clinical trials across the range as opposed to less than 40 clinical trials from our closest competitor); therefore, where a lack of viable evidence exists, our company policy is to err on the side of caution as the health of our customers is of paramount importance to us.

    If pregnant women feel that they would specifically like to take S. boulardii whilst they are pregnant, then we advise them to discuss this with their doctor.

    In general, though, probiotics are an excellent supplement to take whilst pregnant and breast feeding, and the benefits to mum and child are well documented.
    See our FAQ 'Can I take probiotics if I'm pregnant or nursing?'

    Wishing you and your baby the very best of health,


  • Hi i was wondering if i can take Saccharomyces boulardii probiotic alongside the for every day strain. I suffer from severe IBS and most things i eat cause bloating and discomfort. I have recently started the for every day strain so was wondering if i can incorporate Saccharomyces boulardii too. Any feedback would be appreciated. Thanks

  • Hello Sadia, and thank you for your question.

    It's fine to take two or more of our products at any one time according to your individual needs - see our FAQ 'Can I take two OptiBac Probiotics supplements at the same time?'

    So it would be fine to take S. boulardii alongside one of our daily products; in fact, we often recommend this as a desirable combination. S. boulardii is not 'colonising' strain, it's transient which means that it does not take up residence in the intestines. This means it tends to work well with products that contain colonising species and strains, such as 'For every day' or 'For every day EXTRA Strength'.

    For IBS, we'd usually recommend it in cases of IBS-D - for more information on this and other products for IBS, see our FAQ 'Which probiotics for IBS?'

    Very best wishes,


  • I also forgot to mention that i suffer from ibs-c and from all the information i have read it seems saccharomyces boulardii is best for those with ibs-d. Will taking these probiotics make constipation worse

  • I currently suffer from candida. I have heard s.boulardii helps fight off candida. But will i need to be on a strict diet alongside taking these probiotics to fight it off fully? Such as sugar elimination etc? Or will they be just as effective alongside what i usually eat. Thank you

  • Hi again Sadia,

    As a very general rule, yes, S. boulardii is most appropriate for IBS-D; it has a proven track record in helping to alleviate diarrhoea symptoms (see our Research page) and therefore in certain sensitive individuals may make constipation symptoms worse.
    We'd usually recommend a product containing Bifidobacteria lactis BB-12 to help improve regularity - this probiotic strain has been featured in one of the world's largest ever clinical trials on probiotics, and found to improve regularity.

    Some pathogenic bacteria and yeasts can cause constipation symptoms though, so sometimes it can take a combination of probiotics including S. boulardii to rebalance intestinal health.

    For advice regarding your own individual needs, why not contact me directly on [email protected]

    Best wishes.


  • Hi Zara, and thank you for your questions.

    S. boulardii will have an effect on Candida within the body, but if you're looking for an effective long-term solution then, as with any other health condition, supplement interventions will work most effectively in conjunction with a supportive dietary regime.
    For more information about the use of probiotics to support those with Candidiasis, read our new FAQ on 'Which probiotics are best for Candida?'

    Best wishes,


  • Hi
    I have had CFS/ME for several years now and have gradually deteriorated in terms of ailments.
    Whilst my energy levels are improving and I am beginning to walk, talk and do normal, every day activities like cooking shopping and cleaning with ease, I now find myself googling health issues frequently trying to find out what is happening to me.
    Since having ME, I now have bowel issues (recently having a colonoscopy) nothing nasty but awaiting next consultant visit; possible diverticular ??; I also have Prurigo Nodularis and am really struggling with that. I have Candida or Thrush in my mouth and feel like I am drowning !
    On visiting my sister, we sat down and tried to research as much as we could.
    We came to the conclusion, having done a saliva test in water that I needed to get some Daktarin gel to alleviate the thrush, advice from the chemist. We also discussed the root cause of all these issues which, as you may appreciate, is a mine field.
    We made the decision to buy some probiotics aswell (Kidz Immuno), a day before a meal.
    After several days I am already starting to feel the benefits of this action.
    My only concern was taking probiotics for children so researched alternatives.
    I found....Sacardi, Saccharomyces bollard 5 billion with FOS & Vitamin B.
    What would your view be on this bearing in mind my history as stated above ?
    Kind regards
    Jane Evans

  • Hi Jane,

    Thank you for your question.
    Sorry that you've been having such a tough time of it health-wise.

    I can only really advise you regarding the application of our own product range, and I will just say, that it's never a great idea to self-diagnose via Google! :-)

    If you'd like to take a holistic approach to your health, then I'd strongly recommend that you consult with a suitably qualified nutritional therapist or naturopath, who can fully assess your personal, medical and dietary history, then offer you an individualised and appropriate supplement protocol. Check out or to find a professional near to you.

    I've also written a new FAQ 'Which probiotics for Candida' which you might like to take a look at.

    It's possible that probiotics could form a useful part of any protocol for you, however, and I'll write to you directly to make some suggestions that you might find helpful.

    Warm wishes,


  • Hello there.
    I recently had a BIE rest and was told I had an over abundance of this prebiotic in my system which is leading to problems. Is this possible and if so how do I combat it?

  • Hi Connie,

    Thank you for your question.
    Saccharomyces is a probiotic, rather than a prebiotic, which is a substance that helps to feed the bacteria in the intestines. For more about prebiotics, see 'What are prebiotics?'

    Saccharomyces boulardii is a yeast, but is not generally a resident in the body, so it owuld be unusual for it to be causing a problem; however, there are other types of yeasts, such as Candida albicans, that can proliferate and cause problems. Or perhaps the test indicated that you have a global yeast sensitivity?

    It's difficult for me to offer an opinion with so few details, but if you would like more advice about the appropriate application of our product range, then please do contact me to discuss this further. Use the contact form on the Home Page or call in by phone.

    Kind regards,


  • I was just wondering if repoflor will help with severe constipation? I am in brazil with no access to a doctor... and feel severly constipated.


  • Hi, i have been suffering from a chronic yeast infection caused by the pill for the past year. Recently, after so much researching I have learned that probiotics could help the situation. Together with other medication, I started having your probiotics for women. My question is, would the saccharomyces boulardii work fine too? As my pharmacist did not have the women one today and gave me these instead.
    Thanks so much

  • Hello James,

    Thank you for your question, and I'm sorry that you're in such a predicament!

    'Repoflor' is not one of our products, but I wouldn't recommend Saccharomyces boulardii for use in constipation. As this information page suggests, the usual application for this probiotic is in cases of diarrhoea.

    If constipation is your current priority, you may like to read one of my recent articles - click on this link to find out about the strain of probiotic bacteria that was recently featured in one of the world's largest clinical trials on probiotics, focusing on bowel regularity:

    'One of largest ever probiotic clinical trials backs B. lactis BB-12 for regularity'

    Hope this information helps to get things moving for you.

    With warm wishes,


  • Hi Jade,

    Thank you for your question, and your interest in our products.

    Before specific bacteria strains were identified which colonised in the genito-urinary tract, then practitioners often chose to try and support yeast infections by using probiotics to try and displace yeasts from the gut, the theory being that these infections often have their roots in intestinal yeast overgrowth. Improving gut health may still be helpful even if more specific probiotics, like 'For women' are used.
    Saccharomyces boulardii would typically be one of the probiotics used in such a protocol, but for information about this subject, and how different probiotics may help, see our information pages:

    'Will probiotics help to prevent thrush?'

    'Which probiotics are best for for Candida?'

    Hope this helps,


  • Hi,
    I was wondering if you can advise about the use of boulardii in case of resistant Ecoli UTI infection ? Thank you so much


  • Hi Amelia,

    Thanks for your interesting query.
    In the days before strain specific actions were identified, then S. boulardii would have often been used as a natural choice to try and flush out any pathogens that may be hiding out in the intestines and causing issues elsewhere, and I'd always say that it's a great idea to focus on rebalancing gut flora in many chronic health conditions. However, for conditions of the genito-urinary tract, probiotic research has made some incredible leaps and bounds.

    In particular, a couple of strains of bacteria were found in studies to travel through the intestines when consumed orally, and to arrive at and colonise in the female intimate area.These incredibly well-researched strains are Lactobacillus rhamnosus GR-1® and Lactobacillus reuteri RC-14®, which have been clinically trialled by over 2,500 women around the world, and proven to survive to reach the genito-urinary tract.

    So for UTI infections, I'd have to first suggest that you try using a probiotic including strains that colonise where the infection is occurring.
    For more information about this, read our FAQ 'Can probiotics help to cure or prevent cystitis?' and 'L.reuteri RC-14 and L.rhamnosus GR-1 granted vaginal health claim in Korea'

    Warm wishes,


  • Hi,

    My son was give a strong antibiotic ciprofloxacin and codine. He became very anxious and depressed whilst taking it and had to stop. I have been giving him Optibac probiotics (5 billion live cultures - bifidobacterium lactis BB-12, with Fructooligosaccharide fibres). But have just read an article that suggests he should be taking Saccharomyces boulardii. Could you give me some advice please, which would be best, can he take both and for how long. Article I read suggested that the gut is damaged for a year.

    Thank you

  • Hello Kathy, and thank you for your question, and for sharing this interesting study with us.

    Firstly, the reason why Saccharomyces boulardii may be recommended alongside antibiotics is because it’s a yeast and not a bacteria, and so should not be affected by medication. Also because its anti-pathogenic effects may help to prevent undesirable yeasts growing out of control during antibiotic therapy. However, the article is making a general recommendation, which may not be appropriate for every individual. If your son is taking codeine, then due to its ability to slow down stool transit, Saccharomyces boulardii may not be the most appropriate probiotic for him at this time.

    There are others that may be viable alternatives, however, and I'll write to you with my recommendations.

    With warm wishes,


  • My GP thinks I have overgrowth of intestinal flora causing digestive problems. If I take a pro-biotic, will it make it worse?


  • Hi Sally,

    Thanks for your question.

    To offer a professional opinion I would require much more information, as this is a very general query and the answer would depend on many different factors.
    Typically, if there is an overgrowth of pathogenic (undesirable) bacteria in the intestines then probiotics may be used as part of a supplement protocol to help rebalance the gut flora.
    The only instance where some caution may need to be exercised is if there is an overgrowth in the small intestines, known as 'Small Intestinal Bacterial Overgrowth' or SIBO, a situation where even normally beneficial strains of bacteria may overgrow, and I wonder if this is what your doctor is referring to. Even then there are some probiotics, such as the probiotic yeast Saccharomyces boulardii, which can help to normalise the intestinal environment, and are often chosen by practitioners as part of a supplement protocol to address SIBO, followed by other probiotics at an appropriate time.

    Ultimately, however, this is a complex condition to manage and it's important to address the underlying causes of the overgrowth, so we'd always recommend seeking the advice of a suitably qualified healthcare professional (see or to find a practitioner) who can work with your doctor to find the best approach to rebalancing your intestinal health.

    Best wishes,


  • Does it contain living yeast? Can it stop loose motions?

  • Can you advise whether saccharomyces boulardi is safe to use for a 2 year old please? And also what the adjusted dose would be? Many thanks.


  • Dear Susmita,

    Thank you for your questions.
    A good probiotic should always contain live cultures that are capable of surviving transit through the harsh stomach environment to reach the intestines, so yes, if you take a good quality supplement of Saccharomyces boulardii it should essentially be 'living'.
    This amazing probiotic yeast has been extensively researched and demonstrated to be effective in alleviating diarrhoea and loose motions.

    See some of the research studies detailed on our own website:
    Research - Saccharomyces boulardii.
    Hope this answers your question,


  • Hello Alison,

    Thanks for your query regarding the use of S. boulardii in children.
    We recommend the use of this probiotic from the age of 1 year, though some research studies have been conducted on younger children.
    See our 'Research - Saccharomyces boulardii' page.

    In terms of dosage: some studies found just 250mg (5 billion) S. boulardii had a therapeutic effect in children, and we would typically recommend not exceeding half the recommended adult dose for those under 12 years of age.
    It is difficult to 'overdose' on probiotics, however, as our FAQ 'Is it possible to overdose on probiotics?' explains.

    High doses of Saccharomyces boulardii may cause constipation in some individuals.

    I hope that this information is helpful,