Diet Rich in Ultraprocessed Grains Ups Risk for IBD

Diets high in packaged breads, cookies, and other highly processed grain products may raise the risk for inflammatory bowel disease (IBD), while minimally processed grain products may offer some protection, a large study has found.

The sweeping analysis of 124,590 adults from 21 countries found that those eating at least 19 g of ultraprocessed grains a day were about twice as likely to be diagnosed with IBD as peers eating less than 9 g daily.

“Our study adds robust evidence from a large, diverse global cohort that frequent consumption of ultraprocessed grains is associated with an increased risk of developing inflammatory bowel disease,” Neeraj Narula, MD, MPH, gastroenterologist and associate professor of medicine, McMaster University, Hamilton, Ontario, Canada, told Medscape Medical News.

The study also “further clarifies that not all grains carry risk — minimally processed grains like fresh bread and rice were associated with lower risk even. These results build on and specify previous findings linking ultraprocessed foods more broadly to IBD,” Narula said.

The study was published online on August 4 in The American Journal of Gastroenterology.

Diet Matters to IBD Risk

According to the latest US data (2021-2023), ultraprocessed foods made up 62% of daily calories for young people and 53% for adults in 2021-2023.

The Prospective Urban Rural Epidemiology (PURE) study has followed participants aged 35-70 years for a median of nearly 13 years. At enrollment, volunteers completed country-specific food-frequency questionnaires, enabling researchers to quantify usual intake of more than 130 food items and track new cases of IBD reported at biennial follow-ups.

The researchers classified packaged breads, sweet breakfast cereals, crackers, pastries and ready-to-heat pizza or pasta as ultraprocessed grains because they are refined and typically contain additives such as emulsifiers and preservatives. Fresh bakery bread and plain rice were analyzed separately as minimally processed grain references.

During a median of 12.9 years, 605 participants developed IBD; 497 developed ulcerative colitis (UC) and 108 developed Crohn’s disease. 

Increased intake of ultraprocessed grains was associated with a higher risk for IBD, with hazard ratios (HR) of 2.08 for intake of ≥ 50 g/d and 1.37 for 19-50 g/d compared to intake of < 19 g/d. The increased risk was largely driven by a significantly increased risk for UC (HR, 2.46) and not Crohn’s disease (HR, 0.98).

Among the different ultraprocessed grain products, packaged bread stood out: Consuming ≥ 30 g/d of packaged bread (a little more than one slice) was associated with a greater than twofold increased risk for IBD (HR, 2.11) compared to no intake of packaged bread.

In contrast, greater consumption of fresh bread was associated with a reduced risk of developing IBD (HR, 0.61 for ≥ 65 g/d and 0.45 for 16-65 g/d compared to < 16 g/d).

Increased intake of rice was also associated with a lower risk of developing IBD (HR, 0.63 for ≥ 1 serving/d and 0.99 for < 1 serving/d).

When the researchers widened the lens to all ultraprocessed foods — from sodas to salty snacks — the risk for IBD climbed further.

Participants eating at least five servings a day had nearly a fourfold greater odds of IBD than those eating fewer than one serving (HR, 3.95) — a finding consistent with other data from the PURE study cohort.

What to Tell Patients?

The authors acknowledged in their paper that it’s difficult — if not impossible — to completely avoid ultraprocessed food in the Western diet.

They said their findings support “public health strategies to promote consumption of whole and minimally processed foods while reducing the consumption of highly processed alternatives.”

“I tell my patients that emerging literature shows an association between ultraprocessed food intake and IBD risk, but it’s not yet clear whether simply cutting out those foods will improve disease activity once IBD is established,” Narula told Medscape Medical News.

“However, I still encourage patients to reduce ultraprocessed foods and to follow a Mediterranean-style diet — focusing on minimally processed grains, fruits, vegetables, healthy fats, and lean proteins — to support overall gut and general health,” Narula said.

Reached for comment, Ashwin Ananthkrishnan, MD, MPH, associate professor of medicine, Massachusetts General Hospital, Boston, who wasn’t part of the study, said it “adds incrementally to the growing data on how ultraprocessed foods may affect the risk of IBD.”

“They (and others) have previously shown a link between general ultraprocessed food consumption and risk of IBD. Others have shown that some of this is mediated through refined grains. This study more specifically studies that question and demonstrates an association,” said Ananthkrishnan.

“This should not be used, however, to counsel patients. It does not study the impact of grain intake on patients with IBD. It may help inform population level preventive strategies (or in high-risk individuals) but requires more confirmation since there is significant heterogeneity between the various countries in this cohort. Countries that have high refined grain intake are also enriched in several other IBD risk factors (including genetics),” Ananthkrishnan told Medscape Medical News.

The PURE study is an investigator-initiated study funded by the Population Health Research Institute, Hamilton Health Sciences Research Institute, Canadian Institutes of Health Research, and Heart and Stroke Foundation of Ontario. It received support from Canadian Institutes of Health Research’s Strategy for Patient Oriented Research, Ontario SPOR Support Unit, and Ontario Ministry of Health and Long-Term Care and unrestricted grants from several pharmaceutical companies. Narula declared receiving honoraria from Janssen, Abbvie, Takeda, Pfizer, Sandoz, Novartis, Iterative Health, Innomar Strategies, Fresinius Kabi, Amgen, Organon, Eli Lilly, and Ferring. Ananthkrishnan declared having no relevant disclosures.