Lactobacillus reuteri

What is Lactobacillus reuteri?

Lactobacillus reuteri is a lactic acid bacterium found naturally in the human gut, breast milk and, in smaller numbers, the mouth. Taxonomists recently renamed it Limosilactobacillus reuteri, but most supplement labels still use the older name. Like all probiotics, its effects depend on the specific strain. The National Center for Complementary and Integrative Health cautions that results for one strain should not be assumed to apply to another.

In dentistry, L. reuteri is one of the most studied probiotic species. Researchers have tested lozenges and chewing gums containing specific strains to see whether they can shift the balance of bacteria in plaque and reduce gum inflammation.

What the research says

The strongest results come from trials in people with periodontitis who also received scaling and root planing, the professional deep cleaning used to treat gum disease. In a randomized, placebo-controlled trial of 40 patients, L. reuteri lozenges taken after deep cleaning led to lower plaque, gum inflammation, bleeding and pocket depth than placebo at multiple time points over a year, and fewer patients needed surgery. A meta-analysis of L. reuteri as an adjunct to periodontal therapy found short-term improvements in bleeding and attachment level and a reduction in pocket depth in moderate and deep pockets, but the studies were small and the authors called for larger, longer trials.

For gingivitis without professional treatment, the picture is weaker. A 2020 systematic review and meta-analysis of 10 randomized trials concluded that the evidence for probiotics in gingivitis is weak, and in the pooled L. reuteri data there was no statistically significant difference from placebo for gingival index or plaque index. A broader 2025 meta-analysis found probiotics helped plaque and bleeding in periodontitis studies, but differences in gingivitis studies were not significant.

L. reuteri has also appeared in breath studies. A meta-analysis of probiotics for halitosis that included L. reuteri among other species found short-term improvements in breath odor scores, though the authors noted limited data and variable study quality.

How it’s used in supplements

Oral health products deliver L. reuteri in lozenges, chewable tablets or gum so that the bacteria contact the teeth and gums. Studied products named their strains and doses, and benefits were usually measured alongside regular brushing or professional treatment. When a label lists only “Lactobacillus reuteri” inside a proprietary blend, there is no way to know whether the strain or amount matches the research. Probiotics are generally well tolerated in healthy people, but people with weakened immune systems or serious illness should use them only under medical supervision.