Ultra-Processed Foods Increase Risk of Bowel Disease

Ultra-processed vs. whole foods

 Peter Dazeley/Getty Images

Key Takeaways:

  • Ultra-processed foods make up 50-60% of calories in the typical American diet.
  • Higher intakes of ultra-processed foods are positively associated with a risk of irritable bowel disease, including Crohn’s disease and colitis.
  • Whole food, plant-based diets are recommended to help prevent irritable bowel disease.

New research published in the British Medical Journal investigated whether people who eat more ultra-processed food have an increased risk of developing irritable bowel disease (IBD), such as Crohn’s disease or ulcerative colitis.

Ultra-processed food (UPF) is a category under the NOVA food classification system, which breaks foods down into groups based on their degree of processing. The NOVA classifications are:

  1. Unprocessed or minimally processed foods: Whole foods such as vegetables, fruit, whole grains, beans, nuts, seeds, milk, eggs, meat, etc.
  2. Processed culinary ingredients: Ingredients that make the unprocessed foods taste good such as oil, butter, sugar, salt, herbs, and spices
  3. Processed foods: Minimally altered foods with added salt, oil, or sugar, such as cheese, bottled vegetables, canned fish, fruits in syrup, etc.
  4. Ultra-processed foods: highly processed, convenient, low-cost, tasty products made with sugars, fats, salt, additives, preservatives, and stabilizers, such as soft drinks, chips, candy, ice cream, hot dogs, and chicken nuggets

A high intake of ultra-processed food has been linked to an increased risk of heart disease, type 2 diabetes, depression, and certain cancers. Health professionals recommend eating more whole foods and fewer ultra-processed foods for overall health.

Jonathan Isbill, a dietitian, health educator, and owner of ZigZag Nutrition, says that ultra-processed foods provide little to no benefit for human health in this excessive stage of processing.

“If you look around the US as a whole, UPF comprises 50-60% of our total energy intake and contributes nearly 90% of our energy intake from added sugars,” says Isbill. “UPF contributes to eating patterns that promote inflammation and nutrient deficiencies.”

In this new study, researchers investigated the impact of UPF on irritable bowel diseases such as Crohn’s and colitis.

Researchers have specifically noticed that ultra-processed foods containing non-natural additives such as artificial flavors, sugars, stabilizers, emulsifiers, and preservatives may affect gut health.

What Was Studied?

In this prospective cohort study, researchers looked at food intake data from 116,087 participants in 21 low, middle, and high-income countries around the world, as part of the Prospective Urban Rural Epidemiology (PURE) cohort.

Participants were enrolled in the study between 2003 and 2016, and the median follow-up time was 9.7 years. Participants were given a food frequency questionnaire at baseline to determine their usual dietary intake. The researchers then assessed how many participants were diagnosed with Crohn’s or colitis over the study period and if it was associated with their intake of UPF.

Participants were grouped according to how much UPF they ate daily:

  • Less than 1 serving per day
  • 1-4 servings per day
  • More than 5 servings per day.

What Did the Study Find?

The researchers observed an association between diets high in ultra-processed food and an increased risk of developing IBD.

“For our primary exposure of interest, total ultra-processed food intake, we observed a higher risk for the development of both Crohn’s disease and ulcerative colitis in those with higher processed food intake compared to lower intake,” says Neeraj Narula MD, MPH, FRCPC, Associate Professor of Medicine at McMaster University, Staff Gastroenterologist at Hamilton Health Sciences, and one of the study’s authors. 

Neeraj Narula MD, MPH, FRCPC

For our primary exposure of interest, total ultra-processed food intake, we observed a higher risk for the development of both Crohn’s disease and ulcerative colitis in those with higher processed food intake compared to lower intake.

— Neeraj Narula MD, MPH, FRCPC

Narula explains that participants who ate more than 5 servings of UPF per day had almost twice the risk of developing IBD compared to those with less than 1 serving per day. 

“When we looked at sub-groups of ultra-processed foods, elevated risk was observed for all of processed meats, soft drinks, high-sugar foods, and salty foods/snacks,” says Narula.

Why Do Ultra-Processed Foods Increase IBD Risk?

Ultra-processed foods can be high in salt, sugar, fat, additives, and preservatives, all of which have been linked to health problems when consumed in excess. But do researchers know exactly what may impact IBD risk? The answer is not clear, but there are some ideas.

Narula says that their group’s hypothesis is that it’s related to emulsifiers and preservatives that are added to foods to help stabilize and preserve them. 

“Some basic science literature had shown that chemicals like carboxymethylcellulose and polysorbate-80 have been demonstrated to increase bacterial adherence to intestinal villi, and increase their ability to translocate through the intestinal villi,” says Narula.

The paper also noted that deep-fried food was associated with a higher risk of IBD, possibly due to the quality of the oil or the processing of oil leading to modification of nutrients within the food.

Beth Chiodo, MS, RD, LDN, CHWC, dietitian, certified wellness coach, and owner of Nutritional Living adds that UPF like soft drinks and refined sweets contain ingredients like high fructose corn syrup.

"This has been shown to reduce butyrate-producing bacteria in the large intestine," says Chiodo. "This decrease in good bacteria can lead to an imbalance of bacteria overall, which can promote inflammation in the colon. This inflammation may increase the risk of developing inflammatory bowel diseases like Crohn’s disease and colitis."

So, there are several reasons why UPF may lead to bowel disease. More research is ahead.

Diet to Reduce IBD Risk

The researchers found that white meat, unprocessed red meat, dairy, starch, fruit, vegetables, and legumes were not found to be associated with the risk of IBD. The paper says that "it might not be the food itself that confers this risk but rather the way the food is processed or ultra-processed."

Isbill recommends a whole-food, plant-based diet for anyone with IBD-related symptoms or with an interest in IBD prevention.

“Plant-based diets help support the body’s ability to stay in lower states of inflammation and greater states of restful healing,” says Isbill.

Jonathan Isbill MS, RDN, LD

Plant-based diets help support the body’s ability to stay in lower states of inflammation and greater states of restful healing.

— Jonathan Isbill MS, RDN, LD

Include lots of vegetables, fruit, whole grains, nuts, seeds, and legumes in the diet. Chiodo recommends adding oats to the diet since they break down into short-chain fatty acids called butyrate, which can have an anti-inflammatory effect on the intestines.

Chiodo also recommends consuming foods high in polyphenols, such as apples, grapes, berries, herbs, dark chocolate, and tea, for their anti-inflammatory effects. 

At the same time, cut back on ultra-processed foods, especially those with additives, preservatives, and emulsifiers such as guar gum, carrageenan, polysorbate-80, and carboxymethylcellulose.   

“I urge my clients to start slowly, and work to reduce their intake of ultra-processed foods, one by one,” says Chiodo. She suggested small changes, such as substituting fruit for a candy bar, or roast chickpeas instead of chips. 

What This Means For You:

Stick with more whole (unprocessed) foods, and cut back on ultra-processed foods, to help prevent Crohn's disease and ulcerative colitis. A whole-food, plant-based diet may be beneficial for anyone looking to prevent IBD or lower their levels of inflammation.

6 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  4. Steele EM, Baraldi LG, Louzada ML da C, Moubarac J-C, Mozaffarian D, Monteiro CA. Ultra-processed foods and added sugars in the US diet: evidence from a nationally representative cross-sectional study. BMJ Open. 2016;6(3):e009892. doi:10.1136/bmjopen-2015-009892

  5. Beisner J, Gonzalez-Granda A, Basrai M, Damms-Machado, Bischoff SC. Fructose-induced intestinal microbiota shift following two types of short-term high-fructose dietary phases. Nutrients. 2020;12:3444. doi:10.3390/nu12113444

  6. Nyman M, Nguyen TD, Wikman O, Hjortswang H, Hallert C. Oat bran increased fecal butyrate and prevented gastrointestinal symptoms in patients with quiescent ulcerative colitis-randomized controlled trial. Crohns Colitis. 2020;2(1):otaa005. doi:10.1093/crocol/otaa005

By Cara Rosenbloom, RD
 Cara Rosenbloom RD is a dietitian, journalist, book author, and the founder of Words to Eat By, a nutrition communications company in Toronto, ON.