We all know that eating a diet that's rich in ultra-processed foods can be highly damaging to your health in the long term, especially when it comes to your heart health and weight management. However, new research indicates that the American diet (aka one that's filled with added sugars, hydrogenated oils, and saturated fat for example) may also pose a threat to your gut, too.

According to a new study from researchers at the Washington University School of Medicine in St. Louis and the Cleveland Clinic, eating a diet that's high in sugar and fat can impair the immune system in the gut in both mice and humans. More specifically, this type of diet causes damage to Paneth cells, which are immune cells in the gut that help to regulate inflammation levels.

When these specific cells aren't able to carry out their normal functions, the gut's immune system becomes prone to inflammation, increasing the risk of inflammatory bowel disease. It may also become more susceptible to disease-causing bacteria.

"This is a fascinating study that suggests what I have often counseled my patients on for years," Marvin Singh, MD, a gastroenterologist and founder of Precisione Clinic told Eat This, Not That! "The standard American diet, which is high in unhealthy fats and sugar, is disruptive of the inner ecosystem of the gut microbiome. As a result of that disruption, our immune system is impacted, as 70-80% of our immune system is located in the gut."

As the researchers in the study point out, one does not become obese overnight. Instead, people typically have to consume a diet rich in processed foods and lead a sedentary lifestyle for 20 or 30 years before becoming obese.

With this in mind, it's possible that the Paneth cells in obese adults reach a point of no return, despite positive changes in diet and other lifestyle improvements. Bottom line: Researchers will need to continue to study this in humans to see whether or not this process is reversible.

"These changes happen over time, and if we eat a fiber deficient diet that's high in inflammatory foods, this can be the basis for developing chronic diseases like heart disease, high cholesterol, autoimmune conditions, hormone imbalances, and even Alzheimer's Disease or cancer," Singh says.

"I often help my patients optimize their gut health by sequencing their gut microbiome to understand where the imbalances might be so we can make targeted interventions, and then personalizing their diet recommendations based on that, their genetics, and other factors."

For more, be sure to check out The Worst Foods for Gut Health.