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 boulardii
Saccharomyces boulardii, originally extracted from fruit
There 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.

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 lactis BB-12
    • Bifidobacterium bifidum Rosell-175

  • Human Origin:

    • Lactobacillus acidophilus NCFM®
    • Lactobacillus acidophilus UBLA 34
    • Lactobacillus plantarum CECT 7527
    • Lactobacillus plantarum CECT 7528
    • Lactobacillus plantarum CECT 7529
    • Lactobacillus reuteri RC-14®
    • Lactobacillus rhamnosus GR-1®
    • 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 lactis HN019
    • Bifidobacterium longum UBBL 64

  • Fruit Origin:
    • Saccharomyces boulardii

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.


  • 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,


  • Do you make a probiotic supplement with dairy and fruit origin only (not human).

  • Response from OptiBac Probiotics

    Dear Nancy,

    Thank you for your enquiry.

    Yes, we have a range of probiotics that contain strains that are purely dairy/fruit origin. The probiotics in our range that are free from strains that are of human origin are 'Saccharomyces boulardii', 'Bifidobacteria & fibre', 'For those on antibiotics' and 'For travelling abroad'.

    I would also like to point out that, the strains of human origin used in our products as well as other probiotic supplements are not sourced directly from human faeces. The strains would originally have been extracted from faecal samples and stored, very early on during the research into the strain. In some cases, the strains would have been stored in laboratory storage facilities for decades. These ‘human’ strains now used in supplements will have since been cultured in laboratories on fermentation mediums like dairy, barley and soy; now they are identified and classified by scientists there is no need to source them from human faeces.

    I hope this answers your question. If you do require any further information then please
    feel free to send these via the contact form on the website, or send us an email on [email protected]

    Kind regards,


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