While the full complement of essential amino acids is required for optimal health, individual amino acids have functional roles apart from their inclusion in the body’s structural proteins. There’s glutamine’s potential role in curbing sugar cravings, tyrosine for the synthesis of thyroid hormones, and tryptophan as a building block for serotonin. In addition to these well-known functions, researchers are continually finding new and unexpected roles for particular amino acids.

The amino acid arginine is best known for its role in cardiovascular health. As the precursor to nitric oxide, which is a powerful vasodilator and inhibitor of platelet aggregation, arginine can help reduce peripheral arterial resistance and may be helpful for controlling hypertension. But a recent study has uncovered a new and promising role for arginine: fighting dental cavities.

Dental cavities and other oral health issues have multiple causes. Oral health can be compromised by too much sugar, soda, or acidic beverages, which can lower the pH of the oral cavity and erode tooth enamel. Changes in the oral environment can allow multiple species of bacteria to thrive, and to form biofilms. Depending upon the location, the total number of bacteria, species composition, and three-dimensional spatial arrangement of the constituent species, dental plaque biofilms can cause periodontal disease and cavities. Plaque biofilms are highly resistant to chemical and physical efforts to disrupt them. They are not very susceptible to antimicrobials, and remain viable even after abrasive treatments.

The increased use of antibiotics in the food supply, as well as overzealous prescribing in the medical community, has led to a growing number of antibiotic-resistant pathogenic bacteria. Hard-to-treat infections are becoming more common as a result, but the consequences aren’t limited to what we normally think of as systemic illnesses. Antimicrobial resistance is a problem in dentistry, just as it is in medicine. The mouth is home to myriad bacterial organisms, and their aggregation into biofilms is not dissimilar to the proliferation of bacteria in the gastrointestinal tract: there are both beneficial and pathogenic organisms, and certain conditions can stimulate an overgrowth of the pathogenic strains.

In searching for effective methods to disrupt and dissolve stubborn pathogenic biofilms, researchers have discovered a promising new role for arginine. It was already known that oral streptococci can catabolize arginine, resulting in an increase in local pH, which can counteract the effects of acidic foods and beverages on teeth. Alkali production by oral bacteria via the arginine deiminase system (ADS) reduces the risk for dental caries. In fact, a study that examined this showed that, in individuals with active dental caries, twice-daily use of a fluoride-free toothpaste containing 1.5% arginine resulted in significantly increased ADS activity, and shifted the plaque microbial population to a healthier profile, closer to that of individuals free of caries.

However, the new findings indicate that arginine may benefit dental health by an additional mechanism other than raising the pH of the mouth. In studying multi-species plaque biofilms cultured in human saliva in vitro, researchers found that millimolar concentrations of L-arginine can destabilize and break up dental plaque biofilms and reduce the adhesion of certain bacterial strains to tooth surfaces. Because L-arginine is alkaline itself, which could have confounded the results regarding the pH change, researchers employed L-arginine monohydrochloride (LAHCl), which has a more neutral pH in saliva, and has been shown to be safe for oral administration.

The researchers discovered that LAHCl doesn’t kill or damage biofilm bacteria directly, but rather, it destabilizes biofilms in a concentration-dependent manner. This form of L-arginine doesn’t exhibit bactericidal effects, itself, but when combined with cetylpyridinium chloride (CPC), a common antimicrobial for treating dental plaque, the arginine enhanced the susceptibility of the biofilms’ constituent species to the CPC. Perhaps, after more research, we will see commercially available dental care products that contain L-arginine.

The effects of dietary arginine are different from those of arginine-containing compounds applied topically. But it’s still interesting to note that the richest food sources of arginine are animal proteins (particularly seafood), eggs, dairy, and nuts (especially peanuts)—not a sweet or sugary food among them!