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!

    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.

    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.

    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

  • 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

  • Dear Sadia and Zara,

    Thank you for your comments, we will contact you directly.

    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.

    Kind regards
    Jane Evans

  • 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

  • Hi Jade,

    Thank you for your question, we will be in touch directly.


  • 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,

    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

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


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

  • Hi Amelia, Kathy, Sally and Susmita,

    I will respond individually and directly to you.

    Many thanks for leaving a comment.


  • 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.


  • 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: we would typically recommend not exceeding half the recommended adult dose for those under 12 years of age.

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

    I hope that this information is helpful for you and your patient,