Bad Bugs Love Diet Soda


A new study suggests that the sweetener trehalose has fuelled the rise of Clostridium difficile.


There are numerous reasons to avoid processed foods. They’re often packed with sugar, fat, and salt, and tend to lack nutrients critical to health, such as fiber.


Now, a study published in the journal Nature, suggests that some of the additives that extend the shelf life and improve the texture of processed foods may have unintended side effects on our gut microbiomes.


The evidence suggests that these additives selectively feed certain types of bad bacteria (also called pathogens) in the gut.


You’ve probably heard of Clostridium difficile, it is often referred to as C. diff and tends to strike after you’ve taken antibiotics for something else. The antibiotics kill off the good bugs keeping C. diff out, and the more antibiotics you take, the harder it is to get rid of.




Because many strains of C. diff have developed antibiotic resistance, making them very difficult to treat.


In fact, in extreme cases, a fecal microbiome transplant may be the only way to get rid of recurrent C. diff infections. 


C. diff infections affect almost 500,00 people per year according to the CDC, and around 29,000 of them die as a result.


Researchers at Baylor College of Medicine have been studying C. diff. Some time ago they noticed that more virulent strains were outcompeting less virulent strains in the gut.


So they decided to figure out why.


The scientist searched through more than 200 sugars and amino acids present in the gut to see if C. diff better utilized some food source compared to others.


The results were quite surprising.


Two of the worst C. diff strains have developed a unique ability to utilize a sugar called trehalose.


Why does that matter?

Well, trehalose is a sugar (naturally found in mushrooms) that started being used in processed foods in the 1990s. Its use in foods has skyrocketed since 2001.


The researchers believe that by adding trehalose to processed foods, we have been selectively breeding the worst strains of C. diff.   


In support of this, the researchers point to the timing of recent C. diff epidemics. The virulent strains existed before 2000, but caused very few outbreaks. Only after large quantities of trehalose entered the food supply did they become this deadly.


Now, correlation does not equal causation, and trehalose is unlikely to be the only factor behind the C. diff epidemic. However, when testing their hypothesis in C. diff-infected mice, researchers found that mice consuming the sugar fared much worse than mice not consuming the sugar.


This research adds to a to a growing body of evidence suggesting that common food additives can push our gut microbiomes in unhealthy directions, not only aiding the emergence of new pathogens, but also promoting diseases such as obesity, diabetes, and inflammatory bowel disease.




Collins, J. et al. (2018) Dietary trehalose enhances virulence of epidemic Clostridium difficile. Nature, 553, pages 291–294 doi:10.1038/nature25178