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Artificial Sweeteners & Your Gut

Sunday, December 10, 2017

The claims surrounding artificial sweeteners are consistently contradicting, right? 


We hear it all the time…

“Artificial sweeteners will make you fat”

“Artificial sweeteners are linked to cancer”

“Artificial sweeteners are perfectly safe!”

And so on…


With all of these claims, it’s difficult to derive any sort of conclusion on artificial sweeteners and whether or not you should have them. But regardless of our conclusions, we cannot ignore the fact that artificial sweeteners are everywhere. That is one thing that we DO know. 


Non-caloric artificial sweeteners are sugar substitutes and food additives that provide a sugary taste but have significantly less calories than pure sugar. There are a few different types of sugar substitutes, natural vs. synthetic. Stevia is an examples of natural sugar substitutes, while sucralose, aspartame, acesulfame K, and saccharin (and many more) are synthetic.


Common brands that might be easier to recognize that contain these artificial sweeteners are: Equal, NutraSweet, Sweet n’Low, and Splenda.



Since these sweeteners are essentially everywhere we turn, a question that should be asked is: What are the potential health implications of consuming these sweeteners long-term?


Personally, I have been particularly interested in the potential adverse affects in the gut, specifically since our gut is a major root to illness. But unfortunately, the answer is not all that easy to identify. 


Non-caloric artificial sweeteners are recognized as safe for consumption by the FDA and are generally looked at as a beneficial addition to one’s diet due to their low caloric content. However, the supporting scientific data remains inconclusive and sparse. Due to the fact many studies are conducted on mice and there haven’t been many human trials, evidence can be quite inconclusive. But the studies I am about to reference may provide you with some insight.


So let’s dive in, shall we?


Animal Trial #1:

It has been shown that non-caloric artificial sweeteners make mice glucose intolerant. In a study, conducted by Suez et al., three different groups of lean 10-week old mice were given drinking water with sucralose, aspartame, or saccharin added in. There were several other groups of mice that were given regular drinking water without anything added and two other groups that were given water with glucose or sucrose (normal sugars). The purpose of these groups was to see how the artificial sweeteners compared to the normal sugars and to the mice who didn’t consume either.


To assess the changes in the mice, all of the mice were put into a fasted state and only given water 6 hours before a glucose tolerance test was performed (artificial sweetener and glucose and sucrose feeding was stopped during this time frame). 


After being fed 40mg of glucose and having their blood tested immediately before and at 15, 30, 60, 90, and 120 minutes after glucose ingestion, the researchers were able to create a glucose tolerance curve to determine the following:

  • Fasting glucose levels

  • Glucose spiked in the blood

  • How quickly glucose leaves the blood


The results:

Shockingly (but also not so shockingly) enough, at week 11 of feeding, the mice that were fed solely water, water & glucose, and water & sucrose.. had glucose tolerance curves that were very close to one another.  However, the mice that were given water & saccharin, water & sucralose, and water & aspartame all had developed significant glucose intolerance. Of those three artificial sweeteners, saccharin shows to have the largest effect on glucose intolerance. 


To further demonstrate these results, Suez and colleagues conducted the same study on obese mice and observed the same results.


So what does this mean?  This means that ingestion of non-calorics artificial sweeteners caused glucose intolerance in mice, whereas consumption of natural sugars did not.


Animal Trial #2:

In another study conducted on mice, male mice received sucralose in their drinking water for 6 months. Using various testing methods, microbiota composition and metabolites between control mice receiving only water and sucralose-receiving mice were tested.


The results:

The results indicated that sucralose affects the gut-microbiota and its developmental dynamics. Bacterial pro-inflammatory genes and disruption in fecal metabolites were also observed. This suggests that prolonged consumption of sucralose in high doses may increase the risk of developing tissue inflammation by disrupting the gut-microbiota. This claim is supported by the elevated pro-inflammatory gene expression in the liver of the sucralose-treated mice.


In short, chronic consumption of sucralose encouraged chronic inflammation.

Human Trials:

What about evidence involving humans? Have any human studies been conducted? 


The answer to that question is yes, but few… and many of the human studies previously conducted have resulted in mixed outcomes. However, Suez et al. from Animal Trial #1, decided to dig deeper and go beyond mice. They conducted a study on humans. 


A cross-sectional study was conducted via a food intake questionnaire to measure consumption of artificial sweeteners and they also looked at certain clinical measures of metabolic syndrome.


Positive correlations between artificial sweetener consumption and clinical parameters relating to metabolic syndrome were observed. Measures such as weight, waist-to-hip ratio, fasting blood glucose, hemoglobin A1c, glucose tolerance testing, and ALT.


Now, correlation does not equal causation. So seeing that there is a positive correlation between individuals that have a higher BMI and consume artificial sweeteners is not surprising. Artificial sweeteners are typically consumed more-so in individuals that are overweight in an attempt to lessen caloric intake. However, Suez et al. took this into account, corrected for BMI, and still observed the same results.


As I just said though, correlation does not equal causation. We cannot make definitive conclusions from correlations. But the last human trial I am going to discuss, gives us a little bit more to go on. Suez et al. continued their research further by conducting a longitudinal study (a research method in which data is observed and gathered over a period of time). Seven heathy volunteers who do not typically consume non-caloric artificial sweeteners or foods containing them were observed for 7 days. Throughout days 2 through 7, volunteers were given three evenly divided doses of the FDA’s upper intake limit of saccharin at 5mg/kg bodyweight per day. The participants were monitored daily via continuous glucose measurements and glucose tolerance tests. 


The results:

In just a week-long period, 4 out of 7 individuals developed poorer glycemic index responses and significant changes in gut-microbiota composition. The remaining 3 individuals had no change.


This shows that artificial sweeteners absolutely can have a major impact on human gut-microbiota and glucose-tolerance.

As if the results of these studies are not enough... in 2016, Splenda was placed in the “Avoid” category by the Center for Science in the Public Interest.


“We recommend that consumers avoid sucralose, or Splenda, and we recommend consumers also avoid saccharin, aspartame, and acesulfame potassium,” said CSPI president Michael F. Jacobson. “That said, the risk posed by over-consumption of sugar and high-fructose corn syrup, particularly from soda and other sugar-sweetened beverages, of diabetes, heart disease, and obesity, far outweighs the cancer risk posed by sucralose and most other artificial sweeteners."


Major Takeaways:

  • Non-caloric artificial sweetener consumption in mice and humans may increase the risk of developing glucose intolerance

  • Non-caloric artificial sweetener consumption in mice and humans may increase the risk of developing metabolic syndrome/disease

  • Non-caloric artificial sweeteners may alter the gut-microbiota by promoting the development of pro-inflammatory markers


Please keep in mind that the amounts tested in these studies are at the upper limit of what is recognized as safe by the FDA. Consumption of non-caloric artificial sweeteners in small amounts does not seem to cause any serious affects in the body, but then again more human trials are needed to determine this.


Regardless of what you take away from this post, my advice is to avoid where you can with these types of sweeteners but also not to freak out if you do end up eating an artificial-sweetener-containing-food.


As with anything, be aware of what’s in your food. Eat intelligently, but also practice moderation. 


Bian, X., Chi, L., Gao, B., Tu, P., Ru, H., & Lu, K. (2017, July 24). Gut Microbiome Response to Sucralose and Its Potential Role in Inducing Liver Inflammation in Mice. [Scholarly project]. In Retrieved from


CSPI Downgrades Sucralose from "Caution" to "Avoid". (2016, February 8). Retrieved from


Suez, J., Korem, T., Zeevi, D., Zilberman-Schapira, G., Thaiss, C., Maza, O., . . . Elinav, E. (2014, October 9). Artificial sweeteners induce glucose intolerance by altering the gut microbiota. [Scholarly project]. In Retrieved from


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About the Author 

Hi, I'm Karissa. Thank you for stopping by my blog! I am a certified Integrative Health Coach, certified Personal Trainer, and have my Bachelors Degree in Nutrition Science. I am currently studying to obtain my Masters in Nutrition Science as well as to become a Registered Dietitian. I focus specifically on functional medicine practices and holistic approaches to guide individuals towards optimal health, while still reaching their fitness goals.