Do Ultra-processed Foods Impact Ulcerative Colitis?


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“The Western diet, which includes a high intake of UPFs, has been previously linked to the onset of IBD.”

Ulcerative colitis (UC), is a chronic inflammatory bowel disease (IBD), affecting the colon and rectum, characterized by periods of flare-ups and remission. Recent studies estimate that between 1.6 and 3.1 million Americans suffer from IBD. The prevalence of UC has increased in younger age groups and in countries adopting more Western lifestyles and dietary habits. The precise causes of UC remain unknown, but it is believed to be influenced by a combination of genetic, environmental, and immune factors. One significant environmental factor under investigation is diet. Recent research has pointed towards beneficial effects of a Mediterranean diet and to the potential negative impact of ultra-processed food (UPF) on the progression and severity of UC.

UPFs include sweets, industrial breads, cereals, processed meats, and soft drinks. These foods contain preservatives, emulsifiers, and thickeners, which can impact the gut by interacting with the gut epithelial barrier and immune response or altering the gut microbiome’s makeup and function. While there is widespread agreement about the negative health consequences of UPFs, there has been controversy how to precisely classify and characterize these food products. Ultra-processed foods are typically recognized as industrial formulations that contain little to no whole foods and are consistent of a diet high in refined sugars, unhealthy fats, processed meat, salts, preservatives and other food additives while being low in fiber and micronutrients.

The paper titled, Ultra-Processed Food, Disease Activity, and Inflammation in Ulcerative Colitis: The Manitoba Living With IBD Study, investigates the relationship between UPF consumption and disease activity in adults with IBD, specifically UC. The study, with first author Kathy Vagianos was conducted by a team of investigators under the leadership of Charles Bernstein from the IBD Clinical and Research Centre at the University of Manitoba was published in the June 2024 American Journal of Gastroenterology.

The study aimed to explore whether UPF consumption is associated with increased symptomatic disease activity and intestinal inflammation in adults with IBD. The Western diet, which includes a high intake of UPFs and low intake of whole foods, has been previously linked to the onset of IBD, but its impact on those already living with the disease has been less clear.

The study lasted from June 2015 to May 2017 and involved participants who completed biweekly online surveys over a year. Disease activity was assessed using the IBD Symptom Inventory, and intestinal inflammation was indexed by fecal calprotectin levels, a standard measure of white cell activity in the gut. Dietary data were collected using the Harvard Food Frequency Questionnaire. Participants’ energy intake from UPFs was divided into three tertiles (low, middle, high) to facilitate comparison.

“Participants with UC who consumed the most ultra-processed foods had significantly more episodes of active disease and intestinal inflammation compared to those who consumed the least ultra-processed foods.”

The study included 135 participants, with 65% diagnosed with Crohn’s disease and 35% UC. The findings revealed that participants with UC who consumed the most UPFs had significantly more episodes of active disease and intestinal inflammation compared to those who consumed the least amount of UPFs. Specifically, those who consumed the highest amount of UPFs had an average of 14.2 episodes of active disease, while those who ate the least had only 6.2 episodes. These results remained consistent even after considering factors like age, sex, type of disease, and how long they had the disease. Surprisingly, no significant differences were observed among participants with Crohn’s disease.

There are several important limitations to this study. First, the study’s small sample size is a significant limitation. With only 135 participants, including 47 with UC which were divided into tertiles, the statistical power and generalizability is limited. Additionally, while giving valuable insights over time, the study’s year-long approach introduces some issues. Participants might not have consistently followed the diet recommendations, might not have accurately remembered their food intake (a notorious problem with diet recall studies), and there were possibly differences in how their disease symptoms and inflammation were measured. Furthermore, the study did not account for all potential confounding factors, such as stress, physical activity, and other lifestyle variables influencing diet and disease activity.

“…[The] study results suggests that UPF consumption may play an important role…”

While this was an observational cross sectional study, and did not prove a causal role of UPFs in the frequency of UC flares, study results suggests that UPF consumption may play an important role in symptomatic disease and inflammation in individuals with a diagnosis of UC. The findings highlight the importance of dietary choices in managing IBD. The study supports previous research linking high UPF consumption with the onset of IBD and expands the understanding of how diet impacts those already living with the disease. Reducing UPF intake could be a viable strategy for minimizing symptoms and inflammation in UC patients.

Clinical dietary intervention studies have provided a causal link between diet and UC outcomes. For example, a study involving a Mediterranean diet showed that following such a diet for 12 weeks led to significant improvements in disease activity, inflammation, and gut microbiota composition in UC patients. The Mediterranean diet, rich in fruits, vegetables, whole grains, and healthy fats, was associated with reduced inflammation and better overall health outcomes in these patients. In contrast, diets high in processed foods and low in fiber, characteristic of the Western diet, have been associated with increased disease activity and poorer outcomes in UC patients.

Building on this understanding of diet and its impact on gut health, the traditional Mediterranean diet with its rich variety of anti-inflammatory foods, is a key focus of Dr. Emeran Mayer’s new recipe book ‘Interconnected Plates.’ It artfully combines tradition, science, and the enjoyment of food, offering over 55+ simple, authentic daily meal ideas to incorporate into your diet for better gut health. For more details, check out Interconnected Plates here!

Richard Tirado is a recent graduate from UCLA, where he majored in Biology and minored in Anthropology.

This article was reviewed and approved by Emeran Mayer, MD