McMaster University professor Neeraj Narula has discovered that consuming large amounts of ultra-processed foods (UPFs) can increase the risk of Crohn's disease, but not ulcerative colitis (UC).

Researchers gleaned their results by analyzing data from five previous studies conducted between 2020 and 2022 with a total of more than one million participants, more than half of whom were female.

Narula's study defined UPFs as those with chemical modifications such as artificial flavors or colors. Examples include processed meats such as chicken nuggets, sodas, sauces, certain breakfast cereals, refined sweetened foods, commercially prepared breads and pre-packaged candies, among others.

The findings were published in Clinical Gastroenterology and Hepatology.

"Based on emerging literature, we know that UPFs may have negative implications for your long-term gut health and they have additives and substances in them to enhance their flavor or their shelf lives, including chemicals not in our regular diet. Their intake does increase the risk of Crohn's disease," said Narula, an associate professor in the Department of Medicine and director of the Inflammatory Bowel Disease Clinic, affiliated with the Farncombe Family Digestive Health Research Institute.

"The causes of inflammatory bowel diseases (IBDs) are relatively unknown, and we have theorized that a combination of genetic, environmental and microbial factors are implicated. UPFs shift your microbiome towards dysbiosis, leading the immune system to react against certain microorganisms in the bowel and triggering an inflammatory pathway that leads to Crohn's disease."

Narula said that Crohn's disease is also linked to non-Mediterranean diets, high consumption of red meats, as well as diets low in fiber, zinc and potassium.

He said that IBD rates have increased in North America and Europe from the second half of the 20th century and the incidence is now increasing in the newly industrialized countries of Asia, the Middle East and Latin America. He added that this has happened in tandem with the "westernization" of diets, including increased amounts of UPFs.

"Aside from Crohn's disease, such foods carry other health risks including diabetes, high blood pressure and cardiovascular disease," said Narula.

However, UPFs do not appear to be associated with the development of ulcerative colitis (UC), a condition that is characterized by sudden, acute flare-ups of gut irritation in response to certain triggers.

Narula said that unlike UC, it appears Crohn's disease has a long pre-clinical phase.

"The PREDICTS study taught us that patients with Crohn's disease may have biomarkers present in their blood up to five years before they end up being diagnosed," he said.