Intended for healthcare professionals


Probiotics used in trials should be independently checked microbiologically

BMJ 1999; 319 doi: (Published 17 July 1999) Cite this as: BMJ 1999;319:189
  1. J M T Hamilton-Miller, Professor of medical microbiology (j.hamilton-miller{at}
  1. Royal Free and University College Medical School, London NW3 2PF

    EDITOR—MacFarlane and Cummings report on the use of probiotics and prebiotics.1 Strategies to modulate the flora in a beneficial way may help to decrease the use of antibiotics,2 which has obvious important advantages. It is essential that properly conducted clinical trials are carried out, but most of the studies so far reported have been deficient in many respects.

    When setting up a clinical trial with a conventional (that is, chemical) pharmaceutical agent it is taken for granted that the test substance is pure and totally defined and that the doses used are exactly what they purport to be. This is clearly not, however, the case when probiotics are on trial.

    Bioyoghurts vary widely in the content and nature of the probiotic bacteria that they contain,3 and there is no quantitative information on their packaging. Probiotic supplements do not always contain the stated species and quantitatively are often woefully defective (or even sterile).45 It should therefore be mandatory when trials of probiotics are reported that the test substance (bioyoghurt or supplement) contained a well defined probiotic strain and was independently checked microbiologically for quality and quantity at the outset. Furthermore, ifdifferent batches are used (as is likely for trials with bioyoghurts) such checks should be made throughout the study. Only in this way can evidence based results be obtained that can be used as guidance for application to more general situations.


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