What are human strains? Does OptiBac Probiotics use human strains? Are human strains superior?

When discussing probiotics, the term “human strains” is a rather vague one. It typically refers to a probiotic strain that is derived from the human body.

The scientific definition of a probiotic (Live microorganism which when administered in adequate amounts confers a health benefit on the host) does not stipulate that to be a probiotic the microbe must have a human origin, or be a “human strain”. Probiotics must be able to exert their benefits on the host through growth and/or activity in the human body (Collins et al., 1998; Morelli, 2000). It is therefore the action, and not the source of the probiotic microorganism that is a key factor in choosing a probiotic. The ability of a probiotic strain to remain viable at the target site and to be effective in the human gut should always be verified and tested.

Saccharomyces boulardiiThere are in fact many examples of effective probiotic strains which are not recognised as normal residents of the human gastrointestinal tract. For example, no strain of Saccharomyces boulardii could be described as a “human strain”, and yet this species has been shown in numerous clinical trials[1] to benefit human consumers.

[Right Image: Saccharomyces boulardii, originally extracted from fruit]

There is absolutely no existing scientific evidence that human strains are more capable of binding than non human strains. As “human strains” tend to come from the human faeces, this fact in itself acts as evidence of their capability to survive intestinal transit; a key factor when considering a good probiotic. It does not, however, provide evidence that they can adhere to or colonize the human gut more effectively than a strain which is not considered to be of human origin.

At OptiBac we do not therefore consider the the question of “human strain” to be a relevant criterion for selecting an effective probiotic.

However, for those of you who are still curious, here is a list of our probiotic strains and their specific origins:

  • Dairy Origin:
    • Lactobacillus acidophilus Rosell-52
    • Lactobacillus casei Rosell-215
    • Lactobacillus paracasei Lpc-37
    • Lactobacillus rhamnosus Rosell-11
    • Lactococcus lactis Rosell-1058
    • Bifidobacterium bifidum Rosell-175
  • Human Origin:
    • Lactobacillus acidophilus NCFM®
    • Lactobacillus acidophilus UBLA 34
    • Bifidobacterium bifidum Bb-02
    • Bifidobacterium bifidum Rosell-71
    • Bifidobacterium breve Rosell-70
    • Bifidobacterium breve UBBBr-01
    • Bifidobacterium infantis Rosell-33
    • Bifidobacterium infantis UBBI-01
    • Bifidobacterium lactis Bi-07
    • Bifidobacterium lactis Bl-04
    • Bifidobacterium longum UBBL 64
  • Fruit Origin:
    • Saccharomyces boulardii Unique28

NB. For those concerned about dairy sensitivities, some of the OptiBac range may contain small traces of dairy and are therefore not recommended for vegans or those who are severely allergic to dairy. However we do recommend the whole range for those who are lactose intolerant, as the amount of dairy is negligible, and probiotics aid the digestion of lactose. For further clarification, please see the FAQs.

For more information on the OptiBac Probiotics strains, see Our Probiotic Strains.


1. McFarland, L. V. & Bernasconi, P. (1993) Saccharomyces boulardii: A review of an innovative biotherapeutic agent. Microbial Ecology in Health and Disease; Vol. 6. pp. 157-171.


  • Hi there, you seem to have a great product there. Before I try it, I would like to know where do you get your OptiBac Probiotics strains from? If they are also from humans how do you collect them, or do you grow them in a lab or what?

    Thanks for your answer.


  • Hi Kristborg,

    Thanks for your question.

    The strains are cultured in laboratories to match the DNA of strains originally sourced from human flora. We work with scientists who are working to provide the most up-to-date and credible research and highest-quality products in the field.

    Our probiotic formulas undergo rigorous quality control and safety checks before each batch is despatched for packaging. This includes:

    Safety Checks:

    • Each bacteria is classified biologically without transmissible genes
    • Probiotic strain identity verified
    • Full traceability from raw materials to final product

    Quality Control:

    • Species identification – through sequencing of the 16S rRNA gene – a rapid and accurate identification method in microbiology.

    • Strain identification – through DNA finger-printing.

    • Antibiotic sensitivity testing – our manufacturers do not allow any transferable antibiotic resistance genes into their strains. They comply with current guidelines laid down by the European Food Safety Authority (EFSA).

    • Bacterial cell counts are taken at each stage of manufacture. From raw & inoculation materials to the intermediate product and then a final count is taken with the finished product.

    I hope that this answers your question and reassures you that our products are of the highest quality. If you need any help or advice in order to choose the best product for your needs, then please contact me directly using the contact form on our home page.

    Wishing you the best of health,


  • Hi Kerry

    How are human strains derived from the human body?

    What is meant by human strains probiotics? What are strains in

    How can you tell whether a probiotic is of human strains if it is not indicated on the label or on the box?

    Thank you & regards.
    B K Chang

  • Dear B K Chang,

    Thank you for getting in contact.

    I believe the best answer to your enquiry can be found in the FAQ section of the website. Please read the dedicated page “What are human strains?

    Wishing you the best of health,

  • Dear Sir, Madam

    I am seeking the human equivalent of B. longum NCC2705 or B. bifidum S17

    Your advice?



  • Dear Binah,

    Thank you for your question.
    Unfortunately, these aren't strains that we carry in our product range, and as far as I'm aware they're not currently available as probiotic supplements.

    It's worth bearing in mind that the strains of bacteria used in probiotic food supplements are not directly sourced from human faecal samples; they will just be strains that were originally extracted during the early research into probiotics from healthy human stool samples. Representatives from these strains have then been stored in microbiology banks, and from these original samples, new bacteria can be cultured under laboratory conditions using an appropriate fermentation medium such as dairy, soy, barley or other foodstuff.

    Wishing you the best of health,