Preservatives are used extensively in food products worldwide. They play a vital role in preventing foods from spoiling or discoloring, extending their shelf life and making sure they arrive safely to supermarkets and other destinations.

Despite the widespread use of preservatives in canned foods, processed meats, snacks and beverages, little is known about how they affect the gut microbiome. Although the U.S. Food and Drug Administration defines the exact concentrations of these preservatives, there hasn’t been a lot of research about the effects of their regular consumption at these levels. However, interest in the role food preservatives play in the gut microbiome is mounting in the scientific community.

A recent study in mice examined how three common preservatives widely used in food—benzoic acid, potassium sorbate and sodium nitrite—affected the diversity of species in the gut. Bacterial diversity is just what it sounds like: different types of bacteria that live in the gut. This diversity is crucial for a healthy gut, as these bacteria form an ecosystem that provides nutrients and supports a metabolism that is vital for both our body and other gut bacteria. This study found that potassium sorbate, which is used to prevent mold, decreases bacterial diversity in the gut.

Other studies showed that these preservatives may lead to an imbalance of the gut microbiome (called dysbiosis) and a leaky gut. A leaky gut happens when the lining of your small intestine gets damaged. This allows undigested food particles, toxins and bacteria to “leak” through your intestines and enter your bloodstream. When this happens, it can cause inflammation and upset the balance of your gut bacteria, leading to various digestive and health issues.

Another type of preservative is lantibiotics, a type of “natural antibiotic” with strong antimicrobial properties. These preservatives can effectively eliminate dangerous pathogens—such as viruses, bacteria or fungi—in food. Nisin, found in milk, other dairy products and meat, is an example of a widely used lantibiotic.

But even preservatives with beneficial properties can also prevent the growth of good bacteria. A recent study of lantibiotics found that while nisin prevents the growth of pathogens, it can also destroy beneficial gut bacteria. Even low concentrations of nisin can modify our gut bacteria. This suggests that consuming high amounts of nisin could negatively impact gut bacteria and disrupt glucose metabolism. Further studies need to be conducted to understand exactly how these changes affect glucose metabolism.

More research is being done to examine how additives and preservatives in our food affect our friendly gut bacteria. In the meantime, one thing is clear: Limiting processed food is the best way to maintain a healthy gut microbiome.