Potential risk of probiotic usage

Concerning the recent review by Henriksson et al. [1] in Expert Opinion on Drug Safety on the topic of so-called ‘probiotics’, this review could not be any more timely. As of the beginning of November, 2005, searching on one of the largest search engine sites (Google) yielded over 1.7 million hits for ‘probiotic(s)’ indicating the popularity of this topic. Although the majority of the claims are associated with nutrition-associated improvements in health, it raises the concern of this ‘two-edged’ non-licensed approach being used for the ‘treatment’ of medical illnesses. Frequently associated with ‘nutraceuticals’ delivery of probiotic microorganisms has been intended to improve human health, for example, such as has been reported for the ingestion of yogurt with active bacterial cultures to improve/restore gut colonisation. Within the literature/online web citations are numerous claims of health improvement from probiotics, many claims with very little, if any at all, peer-reviewed science in support of their usage, nor warnings of concerns or adverse events. Whereas there can be no arguing of the reported benefits reported for lactobacillus in recolonisation of gastrointestinal flora [2], the reoccurring discussion is where the line is drawn between probiotic food supplement and probiotic medical treatment.

Probiotics have been defined by a group of experts convened by the FAO (Food and Agriculture Organization of the United Nations) as ‘live microorganisms administered in adequate amounts which confer a beneficial health effect on the host’ [101]. In the recent review by Henriksson et al. [1], a very thorough and fair overview of the topic, numerous key points of concern can’t be overemphasised. Two points may be expanded upon and/or re-emphasised: 1) the introduction of any viable, non-endogenous microbe into the human host poses some risk, depending on the quality of the exogenous microbial sample introduced and health of the recipient; and 2) any microbe introduced into the host represents a vehicle for transfer of genetic material, including virulence factors and antibiotic resistance genes. To both of these points, although the goal is to introduce non-pathogenic bacteria into the host for ‘health promotion’, all microbial life forms, especially bacteria, have the machinery of physiological processes that allows them to change their metabolism/physiology, and together with their ability to acquire exogenous genetic information – the physiology of the probiotic bacterium or flora that the probiotic comes in touch with can be altered. As the science of probiotics continues to emerge, and the lay person is bombarded with claims of probiotics that stretch into ‘therapeutics’ or ‘prophylaxis therapeutics’ – both a better understanding of the mechanisms behind probiotics positive impact, as well as the risks of probiotic usage needs to be carefully assessed. Ultimately, only expanded basic research and well-planned, placebo-controlled clinical trials will answer these questions. Until then, probiotics should remain ‘under the microscope’ [1] for if you venture through randomly-chosen internet hit websites, one may think that probioitcs can cure everything from diarrhoea to cancer.