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Bittersweet: The Impact of Sugar Substitutes and Sugar Alcohols on our Gut Microbiomes

Ask the Dietitan, General health, Gut microbiome health, Nutrition

Bittersweet: The Impact of Sugar Substitutes and Sugar Alcohols on our Gut Microbiomes

We’ve all been there: trying to cut back on calories or sugar content with the foods we eat. But it’s tough to resist the delicious sweet taste, especially for those of us who have sweet cravings! Sugar substitutes can be a popular addition to foods that have had their sugar removed, but the food companies want to still provide that sweet taste. I’m seeing sugar alcohols and substitutes popping up more and more frequently as America tries to decrease the amount of sugar in our diets. 

What exactly are sugar substitutes and sugar alcohols anyway? Let’s break it down into two categories here and what to look for on the label: 

  • Sugar substitutes: A food additive that adds a sweet taste similar to sugar, but doesn’t contain the energy that regular table sugar does. These are zero calorie and won’t impact your blood sugar. These packs are exponentially sweeter than table sugar, which overtime can actually cause you to have more sugar cravings- yikes!
    • Aspartame (blue pack)
    • Stevia (green pack)
    • Saccharin (pink pack)
    • Sucralose (yellow pack)
    • Monk fruit (luo han guo) orange packet 

    • Sugar alcohols: Don’t worry, these compounds do not contain ethanol which is the alcohol found in alcoholic beverages. These actually occur naturally in foods and come from fruit products.  As a sugar substitute, they provide fewer calories (about a half to one-third less calories) than regular sugar. This is because they are converted to glucose more slowly, require little or no insulin to be metabolized, and don't cause sudden increases in blood sugar (1). Some people can experience gastrointestinal distress by consuming too many sugar alcohols in one sitting.
      • Mannitol
      • Sorbitol
      • Xylitol
      • Isomalt
      • Maltitol
      • Hydrogenated starch hydrolysates 


    Food for thought: see a pattern with most of these sugar alcohols? They mostly all end in -ol. Keep in mind, sugar substitutes and sugar alcohols are very different. Sugar substitutes contain zero calories, whereas sugar alcohols do contain about 2.6 calories/gram. Sugar substitutes can be found in the ingredients section, whereas sugar alcohols can be found on the nutrition label under the “carbohydrates” section, as well as in the ingredients.

    That’s the sweet part. Now, let’s talk about the potential bitter part. How do these compounds impact your gut microbiome? A study (2) ,published in 2019, breaks it down in the information below: 

    Sweetener/Sugar Alcohol: Impact on the Gut Microbiome

    Aspartame breaks down SUPER fast, so it’s really difficult to measure its impact on the gut microbiome. It doesn’t reach the large bowel (where butyrate and other short-chain fatty acids are produced). No data on the potential influences of aspartame on the gut microbiome.


    In mice fed saccharin, Akkermansia muciniphila, a commensal bacterium that exhibits probiotic properties, was underrepresented. Studies indicate that the consumption of saccharin might perturb the gut microbiota.


    The consumption of sucralose decreased the total number of anaerobic and aerobic bacteria, bifidobacteria, lactobacilli, Bacteroides, and Clostridium


    Microbiota can actually degrade Stevia, and therefore it is not absorbed in the upper GI tract. The roots of Stevia actually contain inulin and fructans, which can be food for specific strains of the gut microbiome. 


    Xylitol reduced the abundance of fecal Bacteroidetes and Barnesiella and increased the abundance of Firmicutes and Prevotella in mice fed a high-fat diet with medium-dose dietary xylitol. The combination of lactobacilli (probiotic) and xylitol (prebiotic) had a protective effect against Clostridium difficile- a not so great diagnosis.


    This is naturally found in pears and other fruits. This sugar alcohol is less tolerated than some others due to its high osmotic load (meaning: greater laxative effects, especially in people with IBS). There’s not enough data to date to definitively determine the effects of sorbitol on the gut microbiome, unfortunately. 

    To sum up, there is a lot of concern surrounding the impact of sugar substitutes and sugar alcohols on the gut microbiome. The problem is, there just isn’t enough clinical data and studies to prove a lot. Further studies are definitely needed to have a more firm understanding of the shifts these sugar substitutes and sugar alcohols have on the gut microbiome. Talk with your doctor for more information on what’s best for you. 

    Written by: Kristin Neusel, MS RD LD CDCES