What Happens in Your Mouth When You Eat Sugar

by | Apr 5, 2023 | Diet & Nutrition, Oral Health

Not news: Sugar contributes to tooth decay.

After all, sugar is the favorite food of harmful bacteria and other microbes that live in your mouth. And it’s not just the white crystal stuff you may be envisioning, but all foods that are digested as sugar, such as refined grains (think white flour foods) and starches.

When you feast on these foods, the bacteria feast. They also produce acids, which damage the tooth enamel. When enamel is damaged, pathogens can enter and infect the tooth, all the way down to the living pulp.

No sugars, no damage – or as one excellent paper in the Journal of Dental Research put it, “Without sugars, the chain of causation is broken, so the disease does not occur.”

And that brings us to a review published last summer in Clinical and Experimental Dental Research.

In this case, the authors wanted to “determine the impact of sugar intake on the microbial diversity and bacteria that predominate under these conditions.” In other words, how does sugar specifically affect the types of bacteria that live in the mouth?

They started by searching three major biomedical databases for relevant studies. Nearly 400 made the initial cut, but only 8 met their exact criteria, which included comparison of oral microbiota under low and high sugar intake, and identification of specific bacteria through genetic testing.

Apart from one study, all others reported for high sugar intake conditions a significant decrease in microbial diversity of the oral microbiome and the predominance of several bacterial genera or species, including Streptococcus, Scardovia, Veillonella, Rothia, Actinomyces, and Lactobacillus.

All of those species include specific bacteria known to contribute to tooth decay and gum disease. When you’ve got more of the bad guys and less of the good, the result is a recipe for disaster.

Among the most abundant and prevalent bacteria was the genus Streptococcus, since it is an important colonizer of the oral cavity, especially the teeth, due to the multiple adhesins that allow it to bind to the enamel surface and its ability to produce extracellular polysaccharides that enhance this adherence. The species of this genus have a great capacity for using sugars and promoting oral microbiota dysbiosis through the production of acids, thereby leading to the acidification of the oral cavity and the adaptation of the bacteria to new environmental conditions. Streptococcus mutans belongs to this genus and is the bacteria most studied and associated with dental caries because of its ability to metabolize a wide variety of carbohydrates, its multiple pathways of catabolizing sucrose, its various glycosyltransferase enzymes that promote the accumulation of biofilms and its great capacity of tolerating high concentrations of acids. [emphasis added]

Of course, brushing and interdental cleaning twice daily, along with regular dental visits, can certainly help keep the baddies like S. mutans in check. For good long-term mouth/body health, though, it’s crucial to restore proper balance to the oral microbiome, cultivating more of the good guys, limiting the bad.

Shifting away from sugars and ultra-processed products to real food is perhaps the most crucial step to restoring that balance. Research shows that ultra-processed diets like the typical American diet reduce microbial diversity. This is bad news for oral and whole body health alike.

Including more pre- and probiotic foods also can be helpful, supplementing as needed. (Your doctor can tell you if this is something you should do and, if so, how much of which supplements to include.)

But the first step is stepping back from all the sugar. This could include opting for healthier sugar substitutes such as stevia and monk fruit, or opting for more natural sweeteners such as honey, agave, and maple syrup when a recipe calls for some sugar. Using fruit for sweetener is another option.

Or you could quit the added sugars altogether. It is doable. Need motivation? Check out what these two women experienced as they shifted to a sugar-free lifestyle, here and here.


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