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Eating ultra-processed food and fried food was associated with a greater risk of inflammatory bowel disease (IBD), the large multinational PURE study found.

More ultra-processed food was related to a greater risk of developing incident IBD (HR 1.82, 95% CI 1.22-2.72, for 5 servings or more per day, HR 1.67, 95% CI 1.18-2.37, P=0.006, for 1 to 4 servings per day, compared to under 1 serving per day), reported Neeraj Narula, MD, MPH, from McMaster University in Ontario, Canada, and colleagues.

However, fried food consumption of one serving per day or more was related to the greatest risk of IBD (HR 3.02, 95% CI 1.51-6.03, P=0.006), the authors wrote in .

The authors speculated the association between fried food and IBD might exist because many fried foods, such as chicken nuggets and French fries, are also processed.

The PURE study itself has been controversial among some experts, especially given its prior findings about salt and vegetable intake.

"Diet studies are notoriously difficult to complete, and the biggest drawbacks here are self-reporting of diet and of IBD diagnosis as well as the age of patients since many IBD patients are diagnosed before the 35 year old lower end in this study," Adam C. Ehrlich, MD, MPH, from Temple University in Philadelphia told 麻豆传媒.

"Recently, the study was published showing that the [Specific] Carbohydrate Diet (SCD) and the Mediterranean Diet were helpful to reduce symptoms in patients with known Crohn's disease, so it would not be surprising to learn that ultra-processed and fried foods (basically the opposite of the SCD and Mediterranean diet) may play a role in disease development," added Ehrlich, who was not involved with the research.

Narula told 麻豆传媒 separately that he was surprised that food such as fruit, unprocessed red meat, white meat, vegetables, legumes, starches, or dairy products were not found to be related to IBD.

"Although this study may help provide insight into the potential causes of inflammatory bowel disease, it is unclear whether there will be a benefit for patients to avoid these foods once they have established disease. This should lead to further studies examining the role of exclusion diets free of ultra-processed foods as a potential therapeutic strategy in patients with IBD," he said.

The authors noted that have found the Western diet's refined sugars, and fats (n-6 polyunsaturated fatty acids) with low fiber as all serve as potential IBD stimulating risk factors.

Another failed to establish a link between IBD and ultra-processed food, but only examined a small population (75 participants with IBD). Researchers also suggested additives or preservatives in the western diet could support the risk of IBD. Ehrlich added.

Narula and colleagues examined participants from 21 nations of diverse economic statuses in the Prospective Urban Rural Epidemiology (PURE) study to assess the risk of inflammatory bowel disease from the ingestion of ultra-processed food.

There were 116,087 adult participants, ages 35 to 70, from January 2003 to December 2016. Follow-up occurred at a minimum of every 3 years and median follow-up was at 9.7 years. A validated baseline food frequency questionnaire was given to participants to assess the primary outcome of IBD development, which included ulcerative colitis or Crohn's disease.

Analyses adjusted for covariates such as sex, education, alcohol, age, region, smoking history, energy, body mass index, waist-to-hip ration, and urbanization.

Responses were converted to the serving size, where daily serving intake was computed uniformly across countries. Over half of all multinational participants were female and less than 25% of total participants were current smokers. A total of 467 participants had developed incident irritable bowel disease, including 377 patients with ulcerative colitis and 90 patients with Crohn's disease.

Not surprisingly, North America, South America, and Europe showed the highest consumption (daily servings and grams) of ultra-processed food compared to other world regions. This included soft drink and processed meat consumption as well.

South America ranked first in consumption of refined sweetened foods, followed by the Middle East and South-East Asia. China saw the highest sodium intake.

Ultra-processed food subgroups, such as salty snacks, soft drinks, processed meat, and refined sweetened foods, were also related to increased risk of IBD.

Among refined sweetened foods, the highest risk of IBD was associated with consumption of 100 grams per day or more (HR 2.58, 95% CI 1.44-4.62, P=0.003). Salty food and snacks had similar findings.

Limitations of this study included the use of a self-reported questionnaire in an observational setting, which statistically computed IBD risk frequency. A reviewed validation of the diagnoses was only conducted for 20% of the population. Authors acknowledge the findings cannot be generalized to anyone under age 35. Dietary changes over time were also unaccounted for in analysis.

"There could also be a role for an ultra-processed food exclusion diet in patients at high-risk of developing IBD (i.e., those with multiple family members with IBD), but further study is needed," Narula told 麻豆传媒.

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