Probiotic Oral-Health Benefits May Depend on the Dose


Too often, studies on probiotic supplements focus on efficacious outcomes but not on how the supplement dosage actually changes the bacterial population at the target site.

Too often, studies on probiotic supplements focus on efficacious outcomes but not on how the supplement dosage actually changes the bacterial population at the target site. In a PLOS One-published study conducted at Western University (London, ON, Canada), researchers aimed to study just that. They tested a probiotic lozenge containing the BLIS M18 probiotic strain (Streptococcus salivarius)-a strain studied for its benefits to oral health-in 75 human subjects and examined how much of the “good” S. salivarius bacteria actually survived in the oral cavity, at different dosages.

Why is studying the persistence of probiotics so important? “Previous studies have found that probiotic bacteria do not generally persist more than a few hours or days in the intestinal tract or oral cavity, though there are some exceptions reported for the oral cavity and vagina,” the researchers explain.

Because of this limited survival, it’s crucial that probiotic marketers determine exactly what dosage is needed to ensure that the healthy bacteria survive so that consumers can receive the bacteria’s purported benefits. In the case of S. salivarius, this strain has been shown to produce bacteriocins (toxins produced by good bacteria that, in effect, help limit the growth of “bad” bacteria, such as Streptococcus mutans, which contribute to dental caries), but it can only do so effectively if the bacteria survive and populate the oral cavity.

In the study, the researchers gave subjects one of four probiotic doses, ranging from low (1× 106 colony-forming units, or CFU, of S. salivarius per dose) to high (1× 106 CFU per dose). Subjects consumed one lozenge daily for 28 days after tooth brushing. Researchers studied saliva samples at baseline and then weekly 12 hours after each lozenge treatment.

The researchers discovered that the supplemented S. salivarius bacteria not only survived at a high level in most subjects, but that they did so in a dose-dependent manner-that is, the level of bacterial survival increased as dosages increased. For instance, after one week, 80% of subjects receiving a 100 million–CFU dose and 90% of those receiving a 1 billion–CFU had detectable levels of the probiotic strain. Moreover, subjects showed lower levels of the harmful bacterial S. mutans.

In fact, points out Joseph Evans, executive manager of R&D for Stratum Nutrition (St. Charles, MO), this study showed that an even lower dose of BLIS M18 achieved this effect, whereas a previous study (Burton 2013 J Med Microbiol) showed persistence but at a higher dosage of 3.6 billion CFU for three months. (Stratum Nutrition supplies BLIS M18 on behalf of its developer, BLIS Technologies.)

“This study shows that administration of BLIS M18 at a dose as low as 10 million CFU can elevate salivary levels of M18, a surrogate marker for colonization and efficacy,” he says.

 Also, none of the subjects experienced negative effects in the study, leading researchers to conclude that “Since no widespread perturbation of the existing indigenous microbiota was associated with oral instillation, and given its antimicrobial activity against potentially pathogenic streptococci, it appears that application of probiotic strain M18 offers potential low-impact alternative to classical antibiotic prophylaxis.”


Jennifer Grebow
Nutritional Outlook magazine


Photo © Vuckovic, Edited by Quinn Williams

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