High intake of ultra-processed food ups risk of IBD

People who regularly eat ultra-processed food such as salty snacks, refined sweetened foods, processed meat, and soft drinks, among others, are at higher risk of developing an inflammatory bowel disease (IBD), a study has found.

“As white meat, unprocessed red meat, dairy, starch, and fruit, vegetables, and legumes were not found to be associated with [the] development of IBD, this study suggests that it might not be the food itself that confers this risk but rather the way the food is processed or ultra-processed,” the researchers said.

This prospective cohort study was conducted in 21 low-, middle-, and high-income countries across seven regions across the globe: Europe and North America, South America, Africa, Middle East, South Asia, Southeast Asia, and China.

A total of 116,087 adults aged 35–70 years with at least one cycle of follow-up and complete baseline food frequency questionnaire (FFQ) data (country-specific validated FQs were used to document baseline dietary intake) were enrolled between 2003 and 2016 and followed at least every 3 years.

Of the participants, 467 developed incident IBD (90 with Crohn’s disease and 377 with ulcerative colitis) during a median follow-up of 9.7 years (interquartile range, 8.9–11.2 years). [BMJ 2021;374:n1554]

After adjusting for potential confounders, higher consumption of ultra-processed food resulted in an increased risk of incident IBD (hazard ratio [HR], 1.82, 95 percent confidence interval [CI], 1.22–2.72 for ≥5 servings/day and HR, 1.67, 95 percent CI, 1.18–2.37 for 1–4 serving/day compared with <1 serving/day; p_trend=0.006).

Different subgroups of ultra-processed food, including soft drinks, refined sweetened foods, salty snacks, and processed meat, each correlated with higher risks for IBD. These results persisted for Crohn’s disease and ulcerative colitis with low heterogeneity.

On the other hand, consumption of white meat, red meat, dairy products, starch, and fruit, vegetables, and legumes did not lead to the development of incident IBD.

Several studies have also suggested that Western-type diets that are typically high in protein, fat, salt, and sugar but low in fruit, vegetables, and fibre are associated with increased IBD risk. [Curr Opin Gastroenterol 2012;28:314-320; Mol Nutr Food Res 2012;56:524-535; Front Immunol 2017;8:838]

“We also found higher intake of fried food to be associated with higher risk of IBD. This association might exist because many fried foods are also processed (eg, chicken nuggets, French fries). It could be that the action of frying and the processing of oil leads to modification of nutrients within the food,” the researchers said. [Int J Mol Sci 2017;18:2700; Food Chem 2018;241:51-59]

Preclinical studies in mice models have shown that emulsifiers, which are common in Western diets and include carboxymethylcellulose and polysorbate 80, cause dysbiosis and the thinning of the mucosal layer, as well as induce the development of colitis and colitis-related colon cancer. [Nature 2015;519:92-96; Cancer Res 2017;77:27-40; Gut 2017;66:1414-1427]

In some studies, other additives implicated for such risk included maltodextrin and titanium dioxide. Intake of foods containing these additives could drive the disruption of gut microbiota and the propagation of subsequent immune activation that occurs in IBD, according to the researchers. [Cell Mol Gastroenterol Hepatol 2019;7:457-473; Gut Microbes 2015;6:78-83; Inflamm Res 2007;56:353-361]

“Further studies are needed to identify specific potential contributory factors among processed foods that might be responsible for the observed associations in our study,” they said.