Inflammatory diets, ultra-processed foods may increase Crohn's disease risk

Medical News Today

01-08-2025

Inflammatory bowel disease (IBD) is a group of chronic conditions that damage the intestines and can cause uncomfortable symptoms. Preventing IBD remains a challenge, and research is underway to minimize this risk. A recent systematic review and meta-analyses identified dietary choices that may affect risk for Crohn's disease, a major type of IBD. The study saw benefits from a Mediterranean-style diet and increased risk from diets containing inflammatory and ultraprocessed foods.Inflammatory bowel disease (IBD) is a group of conditions that impact intestinal health. Ulcerative colitis and Crohn's disease are the major IBD subtypes.A systematic review and meta-analyses published in eClinicalMedicine examined how food can affect the development of IBD, ulcerative colitis, and Crohn's disease. The researchers did not find consistent associations between food choices or food patterns and the risk for developing ulcerative colitis. However, they observed that ultraprocessed foods and eating an inflammatory diet increased the risk for Crohn's disease.In contrast, the findings suggest that following a healthy or Mediterranean diet, consuming high levels of fiber, and eating minimally processed or unprocessed foods might decrease the risk for Crohn's disease. How does diet impact Crohn's or ulcerative colitis?There is a need for more data and analysis on diet and people's risk for IBD, which is what this study focused on. Researchers identified relevant studies from three electronic databases and conducted a systematic literature review. All studies were either case-control studies nested in prospective cohorts or prospective cohort studies. The studies assessed people's diets before they were diagnosed with Crohn's disease or ulcerative colitis and reported on the diagnosis of these conditions or just IBD. The studies also looked at the relationship between risk for IBD, Crohn's disease, or ulcerative colitis and food exposure. The final systematic review included 72 studies. Most studies involved adults, but some involved children. Researchers examined data from over 2 million participants with an average follow-up of almost 13 years. Among the participants, 4,617 experienced ulcerative colitis, and 1,902 experienced Crohn's disease. The researchers also conducted meta-analyses, looking at Crohn's disease and ulcerative colitis separately. The researchers did not find an association between Crohn's disease or ulcerative colitis and some foods and food patterns. For example, they did not find that eating foods like red meat or eggs increased or decreased the risk for ulcerative colitis or Crohn's disease. Overall, the researchers noted that they did not find a consistent association between food patterns or foods and ulcerative colitis risk.In the systematic review, one study found that following a Western dietary pattern increased risk for Crohn's disease. Two studies also suggested that diets with less intake of vegetables and whole grains and higher intake of low-calorie drinks, red meat, and processed meat increased the chances of developing Crohn's disease. Three overlapping studies from the European Prospective Investigation into Cancer found that the omega-3 fatty acid docosahexaenoic acid decreased risk for Crohn's disease and ulcerative colitis. Two overlapping UK Biobank studies found that fish oil decreased risk for both conditions, and two studies found that two plant flavonoids decreased ulcerative colitis risk. How processed food affects disease riskResearchers identified more associations between foods and risk for Crohn's disease. They found that fiber appeared to decrease the risk of Crohn's disease, and that following the Mediterranean diet decreased the risk. They also found that having a healthy diet that aligns 'with recommendations for prevention of non-communicable diseases,' may decrease the risk for Crohn's disease. Finally, eating foods with no or low levels of processing decreased risk for Crohn's disease. In contrast, following an inflammatory diet increased the risk for Crohn's disease, as well as eating more ultra-processed foods. In the sensitivity analysis, researchers found that the associations were dose-dependent for these major associations with food and food patterns and Crohn's disease. How pregnancy and childhood affect IBD riskWhen looking at diet in childhood, one study found that eating high amounts of fish at one and three years may decrease ulcerative colitis risk, eating a high-quality diet at one year may decrease IBD risk, and drinking low amounts of sugar-sweetened beverages may decrease IBD risk. One study suggested that diet diversity during pregnancy may help decrease the risk of the offspring developing ulcerative colitis. Two abstracts further suggest that eating high amounts of lean fish and n-3 polyunsaturated fatty acids during pregnancy decreases IBD risk in offspring and that diet diversity during pregnancy decreases offspring's risk for Crohn's disease. Study author Professor Jean-Frederic Colombel, Director of the Susan and Leonard Feinstein IBD Clinical Center at Icahn School of Medicine at Mount Sinai, New York, summed up the main findings of the research to Medical News Today: 'In this systematic literature review and in meta-analyses based on 72 prospective studies, we examine the association between pre-disease diet and the risk of inflammatory bowel disease. The main findings were that inflammatory and ultra-processed diets were associated with a higher risk of Crohn's disease, while Mediterranean, healthy diets, unprocessed/ minimally processed foods, and high fiber intakes were associated with a lower risk of Crohn's disease.'What the study may be missingIt's possible that some relevant data was missed due to the methods and criteria researchers chose to use. Researchers acknowledge that classification bias is possible for participants' exposure to ultra-processed foods. They also note the possibility of residual confounding bias. They also had limited information regarding certain foods and food patterns. For example, they only had one study that looked at the difference between sugar-sweetened and artificially sweetened beverages. Most studies relied on questionnaires to collect data about participants' food intake, so there is a risk for memory bias, and some only had baseline questionnaires from participants. There were some differences between studies regarding how the Mediterranean diet was defined and scored. Additionally, some studies used differing methods to measure inflammatory diets. Most of the studies were conducted in Europe and the United States. A lot of research focused on white participants, so work in additional groups may be warranted. Since most participants were older or middle-aged, it's possible that the results may not apply to younger individuals. While the risk is small, reverse causality is possible when it comes to the link between ulcerative colitis and Crohn's disease risk and foods. Another small risk is that the link between Crohn's disease and dietary patterns could be obesity-mediated. Finally, there were additional limitations in the studies. For example, in at least one study, IBD status was self-reported by participants, which could have been inaccurate. More research is required to further understand the relationship between food and ulcerative colitis. More examination of certain foods and food patterns may also be helpful. What this study means for people with IBDThe authors of this research explain that this data can help with prevention trial designs and IBD prevention. The data suggest the differences between how diet affects ulcerative colitis and Crohn's disease. Emma Halmos, Associate Professor of Gastroenterology Research & Dietitian at the School of Translational Medicine, Monash University, who was not involved in the study, explained that 'the findings coming from this study are [that] there is likely a difference between the role of diet in Crohn's disease and ulcerative colitis development. Features of a healthy diet, such as having an adequate intake of dietary fiber and limiting ultra-processed food, that is also in line with a Mediterranean diet that encourages plant-based foods and limits protein from meat, reduces the risk of developing Crohn's disease, but not ulcerative colitis.' Finally, it also indicates the need for more dietary discussions. Neeraj Narula, associate professor and gastroenterologist who focuses on IBD research, who was not involved in the study, explained: 'These findings strongly support the idea that dietary counseling for patients with increased risk of Crohn's disease, or for those with early IBD symptoms, should emphasize minimizing ultra-processed food consumption. There is mounting justification for integrating dietitians and nutritional education into standard IBD care, not just as a supportive measure, but as a core strategy for prevention and management.'