- A new study finds that people who eat more ultra-processed foods and less unprocessed foods have an increased risk of developing Crohn’s disease, a condition whose precise causes are not yet fully understood.
- Ultra-processed foods include a variety of commercially produced items that are increasingly found in diets in the United States and around the world.
- Experts believe such foods upset the balance of microbiota in the colon, resulting in gastrointestinal inflammation.
It is unclear what causes Crohn’s disease, an inflammatory bowel disease (IBD) in which the gastrointestinal tract becomes inflamed. Experts suspect it may be some combination of genetic and environmental factors involving the immune system.
A new study from researchers at McMaster University in Hamilton, Ontario considers something more specific.
The researchers found a strong association between consuming large amounts of ultra-processed foods and a heightened risk of developing Crohn’s disease.
The new study is actually a systematic review and meta-analysis of five existing cohort studies conducted between 2020 and 2022.
They investigated a link between such foods and IBD — including Crohn’s disease and ulcerative colitis — and involved more than 1 million people.
The researchers found no significant link between ultra-processed foods and ulcerative colitis.
The meta-analysis appears in Clinical Gastroenterology and Hepatology.
What are ultra-processed foods?
Ultra-processed foods, or UPFs, are foods that are low in dietary fiber, high in saturated fats, contain simple sugars, and include additives such as emulsifiers.
Commercially produced, pre-packaged foods are often UPFs.
Examples include:
- processed proteins, such as chicken nuggets and hot dogs
- cold breakfast cereals
- sodas
- sauce products
- snack chips
- ice creams
- biscuits and some types of bread
- fruit drinks
- refined sweetened foods, such as energy bars, candy, chocolates, jams, jellies, pudding, brownies, and cakes.
Crohn’s disease symptoms
According to the U.S. National Institutes of Health, over half a million people in the U.S. have Crohn’s disease.
Crohn’s is more likely in people who have a family member with Crohn’s, and in people who smoke.
Some of Crohn’s most common symptoms are:
- persistent diarrhea
- rectal bleeding
- abdominal pain and cramps
- urgency of bowel movements
- a feeling of incomplete bowel movements
- potentially damaging constipation.
As a result, a loss of appetite is common, as is weight loss, a lack of energy, and tiredness. In children, Crohn’s can cause growth delays.
While acknowledging he does not personally have Crohn’s disease, Dr. Andrew Gewirtz, a university center professor at Georgia State University, who specializes in research on innate immunity, microbiome, intestinal inflammation, and obesity/ diabetes, who was not involved in the study, said:
“My way of trying to think of how life might be like for them [people with Crohn’s], [is that] I try to imagine that, without warning or known provocation, my body will react as if I have acute infectious food poisoning that completely debilitates me for weeks on end.”
Crohn’s disease can also cause complications beyond the gastrointestinal tract. In extreme cases, surgery may be indicated.
Some research indicates that, with certain treatments, Crohn’s can go into remission, with the gastrointestinal tract returning to normal for extended periods of time. It is also the case that spontaneous remission of Crohn’s occurs for some people.
Ultra-processed foods affect gut microbiota
The recent study proposes that the link between UPFs and Crohn’s may be microbiome dysbiosis, an imbalance of microbiota living in the gut.
“Most processed foods lack fiber, which is needed to nourish microbiota and maintain a mutually beneficial host-microbiota relationship. Many, if not most, processed foods contain detergent-like molecules called ’emulsifiers’ that aid texture and shelf-life,” Dr. Gewirtz explained.
Dr. Gewirtz’s research has shown that the emulsifiers in UPFs interfere with microbiota composition and gene expression. They encourage the bacteria to encroach upon the colon’s otherwise sterile inner mucous membrane, resulting in inflammation.
“We are flooded with chemical food additives in ultra-processed food,” said Dr. Michael A. Kamm, a gastroenetrologist who was not involved in the study.
The incidence of Crohn’s is rising in the U.S. and globally for reasons that are not yet entirely clear.
However, this increase coincides with reported “shifts in the human gut microbiomes primarily seen in industrialized, technologically advanced and economically well-off societies,” explained Dr. Eugene B. Chang, a University of Chicago Biological Sciences professor, not involved in the study, who specializes in the intestinal microbiome.
“This trend has been associated with the emergence of many complex immune, metabolic, neurologic, and neoplastic disorders that were previously less common, or rare, 150 years ago,” said Dr. Chang.
He added that such an “alarming” increase in such disorders over a very brief period of time can only logically be attributed to changes in diet, lifestyle, the environment, and to antibiotic overuse, rather than some sort of genetic drift in world populations.
How to avoid ultra-processed foods
For people who have already received a diagnosis of Crohn’s disease or are experiencing symptoms of the condition, the study’s findings may have arrived too late to offer much help.
“It does not mean that once Crohn’s disease has developed, lowering intake of ultra-processed foods will improve the inflammation,” study lead author Dr. Neeraj Narula cautioned.
Since Crohn’s disease is most typically diagnosed between the ages of 20 and 29 years, a young person hoping to avoid the disease — or simply interested in helping maintain a healthy microbiome — might consider avoiding ultra-processed foods.
According to Dr. Narula, Crohn’s has a long pre-clinical phase during which adopting healthy dietary habits may help change the course of a person’s gut health.
Dr. Kamm suggested a simple rule to stick by when choosing a meal: “Fresh is best.”
Dr. Narula hoped his findings help inform the search for more reliably effective Crohn’s management techniques.
“Studies have been exploring novel diets for Crohn’s disease, including diets which permit none or minimal ultra-processed foods, and these should help us understand the role of dietary management for Crohn’s disease in the coming years,” he said.
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