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 bind to and flush out pathogens such as E. coli and Salmonella; thereby naturally supporting patient gut health in the case of diarrhoea. In fact, research on Saccharomyces boulardii is so extensive, that this strain is registered as a medicine in over 100 countries. S. boulardii has also been shown to have considerable anti-inflammatory properties, helping to maintain gut health in those with Inflammatory Bowel Disease and Irritable Bowel Syndrome. It has furthermore been shown to help clear overgrowth of pathogenic yeasts such as Candida albicans.

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 probiotic species.)

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,