The digestive tract is usually thought of as the esophagus, stomach, and intestines, but it actually begins right in the mouth, where digestion begins. The entire digestive tract, beginning in the mouth, is colonized by microbes. After the colon, the highest count of bacteria per gram is found in the mouth. Just as it’s important to maintain a balance of bacteria in the intestines, it is also important to maintain bacterial balance in the mouth.

A recent systematic review of studies published in the journal Nutrients examined 23 randomized clinical trials of probiotics used for oral health.1 While most of the studies were not designed to detect prevention of caries, or cavities, the researchers concluded, “The use of probiotic strains for caries prevention showed promising results even if only few studies have demonstrated clear clinical outcomes.”

Strains used in these studies include a range of Bifidobacterium and Lactobacillus strains, as well as Saccharomyces cerevisiae. “It is reasonable to affirm that probiotic strains may play a role as antagonistic agents on cariogenic bacteria. In two-thirds of the selected papers, probiotics have demonstrated the capacity to reduce S. mutans counts in saliva and-or plaque regardless of the product or strain used,” stated lead author Maria Cagetti. S. mutans (Streptococcus mutans) has long been considered the major pathogen involved in the development of cavities.

The idea behind probiotic use for oral health is to replace the cavity-producing bacteria with beneficial probiotic bacteria, improving the balance of bacteria in the mouth. Although not completely understood, probiotics are thought to do this in a variety of mechanisms similar to what happens in the gastrointestinal tract: adhesion to the gum and tooth surfaces, competing with harmful bacteria for space, producing organic acids and bacteriocin-like compounds that inhibit harmful bacteria, and by stimulating the immune system as a way to control harmful bacteria. The researchers suggest that continuous probiotic intake is required, since the probiotics do not permanently colonize in the mouth.

Overall, more studies are needed to determine which not only reduce S. mutans in saliva, but which strains also reduce dental cavities. There were many studies not included in this systematic review, including those of the oral probiotic Streptococcus salivarius, which is supported by a number of clinical trials.2 Probiotics are also being studied for their potential prevention of gum disease. In a similar way as probiotics work in the gut to prevent and heal leaky gut, they may also help to prevent and heal “leaky gums,” thereby protecting against periodontal disease.  It may be that a plant-based diet that includes prebiotics like asparagus, artichoke, onions, garlic, leek, chicory, Jerusalem artichoke, wheat and oat (for those not sensitive), as well as soybean, etc., will also be food for the probiotics in the mouth in a similar way as they are in the gut.

Drinking kefir (nonsweetened) is a great way to give your gums a healthy dosage of probiotic bacteria, as well as certain probiotic powders, gums, and chews. I also recommend opening a fish oil softgel and rubbing a high-potency fish oil on the gums as a way to replenish the healthy omega-3s right to the gums. I would not recommend doing this at the same time as taking probiotics since fish oil has some anti-microbial benefits.3

Another similarity between the oral cavity and the gut is the ability of the bacteria and other microbes to form biofilms which is an important part of dental plaque. This can be controlled or broken up with regular flossing which could be done in conjunction with rubbing fish oil on the gums.


  1. Cagetti MG, Mastroberardino S, Milia E, et al., “The use of probiotic strains in caries prevention: a systematic review.” Nutrients. 2013 Jul 5;5(7):2530-50.
  2. Burton JP, Cowley S, Simon RR, et al., “Evaluation of safety and human tolerance of the oral probiotic Streptococcus salivarius K12: a randomized, placebo-controlled, double-blind study.” Food Chem Toxicol. 2011 Sep;49(9):2356-64.
  3. Correia M, Michel V, Matos AA, et al., “Docosahexaenoic acid inhibits Helicobacter pylori growth in vitro and mice gastric mucosa colonization.” PLoS One. 2012;7(4):e35072.