Increasing your risk of IBD through processed food

Thought LeadersDr. Neeraj NarulaAssociate Professor of MedicineMcMaster University

In this interview, News-Medical speaks to Dr. Neeraj Narula about ultra-processed food and how this can increase your risk of developing inflammatory bowel disease (IBD).

Please could you introduce yourself and tell us about what inspired your latest research into processed food and inflammatory bowel disease (IBD)?

I’m a gastroenterologist at Hamilton Health Sciences and associate professor of medicine at McMaster University in Hamilton, Ontario, Canada.  A few of my South Asian friends and family who live in Canada have developed IBD, and I’ve long been interested in determining what environmental factors exist in the Westernized nations that may increase the risk of IBD development as compared to developing nations like India.

One clear difference is the types of food we eat – in particular, many of the foods in Westernized nations contain high amounts of many non-natural ingredients and additives such as artificial flavors, sugars, stabilizers, emulsifiers, and preservatives.   Detergents and emulsifiers that are added to foods may have a detrimental impact on the gut barrier, as some translational science research papers have demonstrated increased intestinal permeability (or 'gut leakiness') with the consumption of these ingredients.

Increased intestinal permeability is thought to be a key part of the pathogenesis in IBD, so my colleagues and I wanted to evaluate if there was a relationship between higher processed food intake and the development of subsequent IBD.  

What is meant by the term ‘ultra-processed food’?

The processing of food basically means changing a food from its natural state.  This can be done by adding simple ingredients like salt or oil, or more complex ingredients like preservatives or emulsifiers.  Ultra-processed foods refer to those that are highly processed and may contain additives like artificial colors, flavors, or stabilizers.

Examples of these foods include soft drinks, hot dogs, cookies, cakes, cold cuts, etc.

Ultra-Processed Food

Hot Dog and Soft Drink. Image Credit: Olga Nayashkova/Shutterstock.com

What is IBD and is there any genetic predispositions that can increase the risk of this disease?

Inflammatory bowel diseases (IBD), consists of Crohn’s disease (CD) and ulcerative colitis (UC), are chronic inflammatory disorders of the gastrointestinal tract.  It is commonly believed that changes in the gut microbiota that occur genetically predisposed individuals can lead to activation of the immune system and leads to the damage of the bowel that we observe in IBD patients.

Previous research has suggested that IBD is more common in industrialized nations. Why is this?

We don’t know for sure.  But it is thought to be due to environmental differences that exist in industrialized nations as compared to developing ones.  

Common hypotheses for differences between industrialized and developing nations that could predispose to IBD include differences in diet,  exposure to air pollutants and heavy metals, exposure to early-life antibiotics, among others.

Can you describe how you carried out your latest research into ultra-processed food intake and IBD?

This study was conducted as part of the PURE study, which is an ongoing observational prospective cohort study that has been ongoing for almost 20 years.  More than 130,000 participants were recruited across 21 countries.

PURE was designed with cardiovascular outcomes in mind, and as a result, focused recruitment mainly on adults between the ages of 35 and 70.  At recruitment, participants completed several baseline questionnaires, including a food frequency questionnaire, and also donated blood which was processed and frozen for future analyses.

For this study, our exposure of interest was processed food.  We included any food which contains additives, artificial flavors, colors, or other chemical ingredients within our definition of processed food.  We also conducted some exploratory analyses to examine other dietary variables which have previously been reported to be associated with or protect against the development of IBD.

Our outcome of interest was the development of Crohn’s disease or ulcerative colitis during the follow-up period.  We adjusted for many confounders that could potentially also impact the development of IBD.

What did you discover?

For our primary exposure of interest, total 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.

Those with more than 5 servings per day had almost twice the risk of developing IBD compared to those with less than 1 serving per day.

Irritable Bowel Disease

Inflammatory bowel disease. Image Credit: Chinnapong/Shutterstock.com

Were there any foods that did not show an increased risk for IBD?

Several!  We did not find any association when we looked at white meat, red meat, dairy, starch, fruits, vegetables, and legumes.

We did find that higher fried food intake was also associated with a higher risk of IBD, although many fried foods are also processed foods, like fish sticks for example, so there may be some overlap here.

Where there any limitations in your research? If so, what were they?

Definitely.  These are laid out in detail in our paper.   But overall, although we were able to adjust for many variables through our multivariable models, there is still a possibility of residual bias due to unknown, improperly measured, or unmeasured confounders due to the observational nature of our study.

Do you believe that with further research into the effects of different diets and IBD, a clearer link can be determined?

Definitely.  This is a hot topic in the field of IBD, and I anticipate several exciting developments over the next 5 years that will help advance our field.

What are the next steps in your research?

Our study found an association between higher processed food intake and the development of subsequent IBD.  For those who already have IBD however, it is uncertain if excluding highly processed foods will lead to disease improvement.

Once the inflammatory cascade has started, it's likely too late for changes in diet to make any significant improvement in the disease course. That said, we are exploring dietary modifications that could be used as part of the therapeutic management of patients with Crohn’s disease.

Where can readers find more information?

About Dr. Neeraj Narula

Currently employed as an Associate Professor of Medicine at McMaster University and Staff Gastroenterologist at Hamilton Health Sciences, with a clinical and research focus in Inflammatory Bowel Diseases (IBD).Dr. Neeraj Narul

  • Over 80 peer-reviewed publications and 4 book chapters
  • Almost $2 million in research funding and grants
  • Recently awarded Meeting of the Minds Junior Investigator Award (2020), Crohn’s and Colitis Rising Star Award (2019), and McMaster University Department of Medicine Internal Career Award (2018)
  • Advanced Training includes Present-Levison Advanced Inflammatory Bowel Diseases Fellowship at Mount Sinai Hospital (New York, NY) and Masters of Public Health at Harvard TH Chan School of Public Health (Boston, MA)
  • Invited speaker at several international congresses including Digestive Diseases Week (American Gastroenterology Association), European Crohn’s and Colitis Organization Conference, United European Gastroenterology Week, and Ontario Association of Gastroenterology Annual Meetings
  • Leadership roles within several national organizations, including VP-Treasurer for the Canadian Association of Gastroenterology, and Vice-President of the Canadian IBD Research Consortium
Emily Henderson

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Emily Henderson

Emily Henderson graduated with a 2:1 in Forensic Science from Keele University and then completed a PGCE in Chemistry. She loves being able to share science with people all over the world and enjoys being at the forefront of new and exciting research. In Emily's spare time she enjoys watching true crime documentaries and reading books. She also loves the outdoors, enjoying long walks and discovering new places. She goes camping monthly and recently climbed Ben Nevis. In the future, Emily wants to have travelled all over the world, learning about new cultures. She has an extensive bucket list and is keen for new adventures!

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