Safety ofLactobacillusStrains as Probiotic Agents

Abstract

SIR—Although I agree with Sipsas et al. [1] that any report of organisms causing disease needs to be taken seriously, I disagree with many of the points they make in their letter. First of all, the original review that they cite [2], although laudable, included several important inaccuracies, starting with a definition for probiotics that the authors of the review appear to have made up. Probiotics should be defined as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” [3, p. 2]. The original review [2] wrongly stated that probiotic products used in Europe differ from those used in the United States, because, for example, Lactobacillus rhamnosus GG is used on both continents. Furthermore, the authors of that review [2] and Sipsas et al. [1] missed a critical point: for a strain of Lactobacillus to be considered a probiotic, it first must have been shown to confer health benefits on the host [3]. Unfortunately, countless numbers of “probiotic” products on the market—and too many organisms cited in the literature as “probiotics”—have never been shown to confer any health benefits on the host. At best, there are a handful of strains for which there is evidence of an associated health benefit [4]. Yet, even with so many pseudoprobiotic products available, which often have unreliable contents [5], very few case reports of side effects have been reported [6].