Down with diet

noartificialsweetenersRebecca Donovan (11 AM Micro) is interested in the normal microbiota. I have had a long-standing interest in the role of the gut microbes, and how recent studies have implicated them in a variety of phenomena–see for instance this report about how gut bacteria play a role in mate selection, or this one about a dating service based on gut bacteria. Rebecca’s summary shows that what we feed those bacteria is as important as the types of microbes themselves. Here’s Rebecca’s story, and for those who read to the end, a BONUS opportunity:

A recent article, published on, discovered that artificial sweeteners may be doing more harm than good in your body. Originally marketed to be the ideal solution to those desiring a lower calorie, “sugar less” way to avoid diabetes, recent research has suggested that artificial sweeteners are actually promoting glucose intolerance in the body. If, by this point, I have not convinced you to put down that diet coke in your hand, please read on.

How does this happen?
According to Dr. Eran Elinav and Professor Eran Segal, both of the Weizmann Institute of Science, our gut microbiota, or the bacteria residing in our intestines, are the likely culprits. To confirm this idea, the scientists gave mice water that contained three of the most readily used artificial sweeteners, saccharin, sucralose (splenda), and aspartame (Equal). They found that giving these mice the artificial sugar water promoted development of glucose intolerance to a much greater extent compared to mice only given plain water (Weizmann Institute of Science, 2014). It is also worth noting that mice who were given water containing real sugar developed less of an intolerance to glucose compared to mice given artificial sweetener water. Next, the scientists “cleaned out” the microbiota in the mice through the use of antibiotics. This “clean sweep” of gut bacteria resulted in a return of tolerance to glucose in mice given artificial sweetener water, solidifying the claim of the researchers that gut bacteria are the “prime suspects” in glucose   intolerance brought on by artificial sweeteners.

How do these findings pertain to humans? (After all, we’re not mice!!!)
The scientists involved in this experiment “covered their bases” by gathering a group of human volunteers, who rarely consumed artificially sweetened products, to add them to their diets for a week. After this time, their blood glucose levels would be measured. Their gut microbiota would also be analyzed and measured. The results of this experiment were that most of the participants exhibited an intolerance to glucose after ONLY ONE WEEK of consuming artificial sweeteners. Further analysis of the gut bacteria of participants illustrated  that, with consideration to those whose intolerance levels towards glucose were not adversely affected, that there are two types of gut bacteria living within humans: a type that reacts negatively to glucose resulting in intolerance and a type that has no effect on glucose tolerance (Weizmann Institute of Science, 2014). The researchers involved in the experiment believe that the aforementioned “bad” gut bacteria “turned on” an inflammatory process in the body, negatively affecting the ability of the body to effectively process sugar.

What should this study teach us?
The ultimate question we should ask ourselves is: why would we want to put substances in our body that are proven to be harmful to us? Diabetes and obesity are still, and will continue to be on the rise, in America if we continue to do little to prevent these diseases from occurring. You can take the first step in preventing diabetes and obesity by eliminating  “diet” from your diet. Artificial sweeteners aren’t worth the risks associated with them.

BONUS added by Singleton: in the comment thread, give an example of an association that the normal microbiota has with ANY aspect of human health (good or bad). No repeats, so read what others have put in, and you must give a citation (URL). Don’t worry about formatting of names–I will fix–but do spell them correctly. Offer ends on the end of the day on Friday September  26th.


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on September 23, 2014, in Bonus!, Guest Post, You are what you eat. Bookmark the permalink. 33 Comments.

  1. If the normal microbiota become unbalanced in the human body, it can lead to different diseases such as inflammatory bowel diseases and chronic human immunodeficiency virus infection. This happens when the intestinal microbiota becomes unbalanced in the body. Link to cite here

  2. Found in the lower intestinal tract, Bacteroides are associated with colitis and colon cancer. Link to cite here

    EDITED by DS to leave other things for other students

  3. The long term impact of antibiotics on normal gut microbiota usually results in decreased colonization resistance, which could lead to future disease and the prevalence of antibiotic resistant strains sitting in the body. Link to cite here

  4. Microbiota in the gastrointestinal tract has an impact on acquired immunity (also known as the adaptive immune system). For example, disruption of normal microbiota can lead to a dysfunction of the acquired immune system. This dysfunction can lead to diseases such as inflammatory bowel disease.

    • So this is pretty similar to the one posted by Sarah above

      • Juli Ignaczewski

        Oh sorry I didn’t realize that using similar examples for different functions wasn’t allowed. The research I found online also referenced that this connection to the immune system could suggest that it is controlled by the microbiota in the gastrointestinal tract, instead of the other way around.

    • Ok; that is fine. There is actually increasing evidence that microbes can modify various aspects of physiology, presumably through sending signals that affect host cells.

  5. Gut microbiota impact behavior in humans and other mammals and are associated with an increase in anxiety-like behaviors. It is thought that this is a result of microbial colonization “turning on” the activity of the neuronal circuits associated with this type of behavior.


  6. Whether a baby is born vaginally or by cesarean section and whether a baby is breastfed or formula-fed, influences the amount of gut microbiota in babies. Infants who were delivered by cesarean section and infants who are formula-fed lacked specific bacteria. This may increase the risk for health problems later in life.


  7. Corynebacteria is a propionic acid bacteria. It is consistent skin flora. It is also found in the nose, pharynx, mouth, lower GI, and vagina. They have been shown to be a cause of acne. Corynebacterium diphtheriae, an agent of diphtheria, is considered a part of the normal flora prior to when the diphtheria toxoid was used. They used the toxoid to immunize against the disease.


    • The corynebacteria are not the same thing as the propionic acid bacteria, although they are somewhat related. I did not know the fact about C. diphtheriae, although it makes sense that it might no longer be a commensal due to vaccination.

  8. This review summarizes the main literature findings about the relationships between gut microbiota and chronic liver disease, both in the pathogenesis and in the treatment by probiotics of the liver damage.

    • The fascinating bit of data from that article is this figure which makes the argument that liver disease such as alcoholic cirrhosis is due to the action of alcohol on the overgrowth of microorganisms, leading to an inflammatory response. liver damage

  9. The presence of Staphylococcus aureus on the human skin most commonly produces a condition known as impetigo. This condition is characterized by irritated soft tissue that eventually ruptures and is healed by the formation of a crust on the external surface of the skin.

  10. Streptococcus mutans is the main bacterium involved in plaque formation and formation of dental caries. This is the occurrence of tooth decay or a cavity, that causes destruction of the hard tissues of the teeth. Dental disease is viewed as an opportunistic infection, caused by pathogens, that in the end can be very costly.


    • I think it could be argued that this is the most significant pathogen affecting US health at present, with regards to the number of people showing disease due to its presence.

  11. Pseudomonas aeruginosa can cause infections of the blood, pneumonia, and infections after surgery that may lead to severe illness or death. The most common group of people to acquire this infection are patients in a hospital, specifically those on breathing machines, catheters, or wounds from surgery/burns. It is spread by employees or equipment that is not cleaned properly.

  12. Bacteroides thetaiotaomicron produces multiple fucosidases that cleave fucose from host glycans, resulting in high fucose availability in the gut lumen.

  13. Samantha McGuigan

    Large amounts of the microbiota Fusobacerium was correlated with the LDL cholesterol, where as large amounts of Steptococcus was correlated to HDL cholesterol levels.

  14. Lactobacillus is a main function in the genital areas especially for women. It helps protect the stratified squamous epithelium in the vaginal area and also help maintain homeostasis of pH levels. Lactobacillus is also located in some dairy products and alcohol as a fun fact 🙂

  15. Fecal microbiota transplantation has been considered as an alternative treatment for intestinal diseases such as irritable bowel syndrome, ulcerative colitis and inflamed bowels. Healthy microbiota can be donated and cultured, then injected into a patients intestines. The hopes in this therapeutic treatment is to restore healthy microbiota in the intestines.


  16. A person’s diet can influence the amount of microbiota in the body. In this study, it was found that people with Celiac disease and people who choose a gluten free health style have lessened amounts of the healthy gut microbiota and increased of unhealthy microbiota than the people who eat a diet with gluten. Citation link here

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