Study data published in BMJ outline the association between ultra-processed food (UPF) intake and subsequent risk for inflammatory bowel disease (IBD). In a prospective cohort study of healthcare professionals around the United States, individuals in the highest quartile of UPF consumption were at nearly 2-fold greater risk of developing Crohn disease (CD) compared with individuals in the lowest quartile.

Investigators extracted data from 3 nationwide cohorts: the Nurses’ Health Study (NHS) (1986-2014), the Nurses’ Health Study II (NHS II) (1991-2017), and the Health Professionals Follow-up Study (HPFS) (1986-2012). In each of these cohorts, questionnaires were mailed to participants at baseline and every 2 years thereafter to capture clinical history and lifestyle factors. Diet was assessed using validated, semi-quantitative food frequency questionnaires.

The current analysis included NHS, NHS II, and HPFS participants who completed at least 1 detailed food frequency questionnaire at enrollment. Individuals with prevalent IBD at baseline were excluded. Food intake was categorized as the following: unprocessed or minimally processed foods, processed culinary ingredients, processed foods, and UPFs. UPF consumption was defined as the percentage of total energy consumption from UPFs.


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The primary outcome was diagnosis with CD or ulcerative colitis (UC) during follow-up. Cox proportional hazards models were used to estimate the hazard ratios (HRs) for IBD according to UPF consumption. Models were stratified by age, cohort, and questionnaire cycle and adjusted for demographic and clinical covariates, including race/ethnicity, family history of IBD, smoking status, body mass index, physical activity, medication use, and use of oral contraception.

The present analysis included data from 203,516 women and 41,596 men. Over a total of 5,468,444 person-years of follow-up, 369 cases of CD and 488 cases of UC were reported. The calculated incidence rates for CD and UC were 6.7 and 8.9 cases per 100,000 person-years, respectively. Median age at diagnosis of IBD was 56 (range, 29-85) years.

Participants in the highest and lowest quartiles of UPF intake consumed a median of 46.4% and 21.0% of their total energy from UPFs, respectively. Compared with individuals in the lowest quartile of simple updated UPF consumption, participants in the highest quartile had a significantly increased risk for CD (HR, 1.70; 95% CI, 1.23-2.35; P =.0008).

Certain UPF groups conferred higher risk, including ultra-processed breads and breakfast foods (HR, 1.18; 95% CI, 1.07-1.29 for each 1 standard deviation increase in consumption), frozen or shelf-stable ready-to-eat/heat meals (HR, 1.11; 95% CI, 1.01-1.22), and sauces, cheeses, spreads, and gravies (HR, 1.14; 95% CI, 1.02-1.27).

There was no significant association between UPF consumption and UC risk (P =.25). Intake of unprocessed or minimally processed foods had an inverse association with both risk for CD (HR, 0.70; 95% CI, 0.52-0.94; P =.02) and risk for UC (HR, 0.74; 95% CI, 0.57-0.95; P =.01).

As far as study limitations, investigators cited the mean age of the cohort, which is higher than most long-term studies assessing IBD. Additionally, dietary information was captured by self-report, which prevented a comprehensive assessment of nutritional data. Participants also had a lower proportion of total energy intake from UPFs compared with the overall United States population, limiting data generalizability.

Results from this long-term, nationwide cohort study implicate UPF consumption in subsequent risk for CD. However, UPF consumption did not appear to increase risk for UC. “Further studies are needed to identify specific contributory dietary components among UPFs that might be responsible for increasing the risk of developing CD,” investigators wrote. “Whether the risk of incident CD differs by the duration of UPF exposure and if avoiding UPFs is beneficial to those with an established disease would also require further research,” they concluded.

Disclosure: Several study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Narula N, Wong ECL, Dehghan M, et al. Association of ultra-processed food intake with risk of inflammatory bowel disease: prospective cohort study. BMJ. 2021;374:n1554. doi: 10.1136/bmj.n1554