The Not-So-Sweet Side of Sugar and Our Microbiome

sugar and microbiome

Our closest relative might as well be the hummingbird because, like this sugar-dependent avian species, humans have developed an insatiable (often addictive) appetite and thirst for sugary foods and beverages. But unlike the hummingbird, whose life depends on this sweet stuff (sourcing it naturally from flower nectar), sugar has quite the opposite effect on our health, particularly on microbiomes. 


Shocking Sugar Statistics 


Whether you prefer sweet or savory (bubble burster: sugar is hidden in many savory food items), as a population, we consume way too much sugar. According to the American Heart Association (AHA), American adults consume an average of 77 grams of sugar a day (the equivalent in weight of six 10-pound bowling balls a year!), and children are ingesting upward of 81 grams of sugar daily (30 gallons in a year of which is consumed through sugary beverages!).1


How much sugar is “healthy,” though? The AHA recommends no more than nine teaspoons (36 grams or 150 calories) for men and less than six teaspoons (25 grams or 100 calories) for women of added sugar daily. So, as you can see, we are overdoing it a bit. Aside from sugar being blatantly and surreptitiously added to our go-to packaged and bottled commodities, many of us are actively seeking out sugar because we have developed a dependency on it (sugar is highly addictive). But fret not! Reducing sugar consumption to a healthy level is a totally doable goal, especially after you learn how it affects your oral and gut microbiome and, in turn, your health and happiness. 


Note: If you see high fructose corn syrup, dextrose, sucrose, turbinado sugar, coconut sugar, maple syrup, honey, agave, and/or fruit juice concentrate on the ingredient list, take note that these are sources of sugar despite some sounding healthier than others. 


How Sugar Affects Your Microbiome 


Our microbiomes (skin, oral, gut, etc.) thrive on plant-derived fibers (i.e., a high-fiber diet—the opposite of the traditional Western diet). Believe it or not, we are made up of almost equal parts human cells and microbial cells, so we must consider the dietary needs of the trillions of microorganisms we share our body with, especially since these microorganisms are “rent-paying tenants” that provide invaluable life-sustaining services (i.e., absorbing nutrients and regulating our immune, metabolic, and nervous systems) in exchange for a home and fiber (from fruits, vegetables, legumes, grains). To be frank, though, we aren’t being the best landlords since the traditional Western diet is actually high in saturated fat, preservatives, artificial ingredients, and, you guessed it, sugar instead of fiber. So, what does this mean for our diverse microscopic tenants? 


Research has observed microbial changes such as reduced diversity, increased abundance of Proteobacteria (a disproportionate increase causes unspecific inflammation), and decreased abundance of Bacteroidetes (responsible for downregulation of immune system responses in the gut) induced by high dietary sugar.2 In other words, a high sugar intake can throw off the balance of our microbial community leading to higher oxidative stress (the root of most diseases) and immunological imbalance (70% of our immune system is in our gut).


When we think about our microbiome, we often think about our gut, but our oral microbiome is equally important (our mouth is the main entrance to the rest of our body). It is safe to say that everyone has heard at least once from their dentist that sugar is terrible for your teeth. This is true, but why exactly? 


As proclaimed in a preliminary study of the impact of sugar on the oral microbiome, cavities (also called dental caries) are caused by the demineralization of tooth tissue from the fermentation of dietary carbohydrates by acid-producing bacteria. “Consuming sugar has negative effects on oral health (i.e., periodontal disease), as cariogenic (cavity-causing) bacteria convert monosaccharides (simple sugars) into acids that are detrimental to the teeth.”3 


Teeth are essential for eating, which is, as we all know, essential to life. But beyond controlling cavities, there are microorganisms (over 700 species) in your mouth that are responsible for critical physiological, metabolic, and immunological functions such as digestion of food and nutrition, generation of energy, metabolic regulation, and the detoxification of environmental chemicals, to name a few.4


Our microbiomes are interconnected and play an essential role in keeping us alive and healthy. Health is synonymous with homeostasis, and to maintain health, we must make a conscious effort to sustain balance through our diet, lifestyle choices, and proactive and preventative wellness practices (such as taking pre and probiotics). When our microbiota is imbalanced and normal inflammatory response becomes chronic, we are inherently increasing our risk of metabolic disorders.  

The Connection Between Sugar, an Unhealthy Microbiome, and Chronic Diseases 


Added dietary sugar (i.e., not naturally deprived sugar as found in fruit, for example) provides little if any, nutritional and health benefits. As you’ve just learned, our microbiota doesn’t fare well when inundated with sugar. And in fact, too much sugar can lead to a whole host of diseases in the categories of: 


  • Autoimmune diseases (celiac disease and multiple sclerosis) 

  • Cardiovascular diseases (stroke and clogged arteries) 

  • Gastrointestinal diseases (irritable bowel syndrome and colon cancer)

  • Metabolic diseases (obesity and diabetes)

  • Neural Diseases (depression and anxiety)

  • Oral disease (periodontal disease and dental caries) 



We are inextricably dependent on our microbiota, as they are on us, for our survival. But life, at least modern life, isn’t just about surviving anymore; it’s about thriving. To thrive, we must ensure that the proper diversity and abundance of microorganisms survive in and on us. Their survival and ability to carry life-sustaining services for us depend on the appropriate diet, which, as you’ve just learned, doesn’t include a lot of sugar.


  1. How much sugar is too much? (2022, June 2). Retrieved October 25, 2022, from heart.org 

  2. Satokari, R. (2020, May 8). High intake of sugar and the balance between pro- and anti-inflammatory gut bacteria. Nutrients. Retrieved October 25, 2022, from PubMed Central

  3. Pang, L., Zhi, Q., Jian, W., Liu, Z., & Lin, H. (2022, September 7). The oral microbiome impacts the link between sugar consumption and caries: A preliminary study. Nutrients. Retrieved October 25, 2022, from PubMed Central 

  4. Deo, P. N., & Deshmukh, R. (2019). Oral microbiome: Unveiling the fundamentals. Journal of oral and maxillofacial pathology: JOMFP. Retrieved October 25, 2022, from PubMed Central