A “Western” diet that’s rich in refined grains, processed meats and convenience foods does not appear to increase the risk for developing inflammatory bowel disease (IBD). Neither does a diet high in vegetables, fiber and low-fat meat appear to reduce the risk.
Inflammatory Bowel Disease (IBD) is an immune-mediated chronic inflammatory disease of the gastrointestinal tract. There are two types of IBD, Crohn’s disease and ulcerative colitis; both manifest as chronic immune-mediated inflammation and cause similar symptoms. It is estimated that 1.4 million Americans have IBD, which tends to run in families and affects males and females equally.
Hamed Khalili, MD, instructor in medicine in the Division of Gastroenterology at Harvard’s Massachusetts General Hospital, and his colleagues analyzed prospectively collected “food frequency questionnaire” responses from 181,843 women who participated in two national Nurses’ Health Studies. The two studies were launched in 1976 and 1989, respectively, and evaluated participants approximately once every four years.1
The study authors split the nurse respondents into two groups based on their dietary patterns: a “prudent” diet, which consisted mainly of vegetables, fruits, legumes and poultry; and a “Western” diet, dominated by refined grains, processed and red meats, convenience foods, desserts and sweets, potatoes, high-fat dairy, and sugary beverages.
None of the participants had IBD at the beginning of the study and 256 were diagnosed with Crohn’s disease and 318 patients with ulcerative colitis over a total 24-year follow-up period.
After comparing IBD cases with non-IBD controls according to both Western and prudent diets, the Harvard team found no significant differences in the risk for IBD associated between either dietary pattern. Importantly, no difference in the development of IBD was found even when controlling for age, smoking, body mass index, physical activity, and use of oral contraceptives, menopausal hormone therapy and non-steroidal anti-inflammatory drugs use.
The results of the current study however are in contrast to another study of more than 180,000 women which suggested that dietary fat, omega-6 polyunsaturated fatty acids and meat are associated with an increased risk for IBD.
Experts agree that the pathogenesis of IBD is complex and the importance of genetics was not controlled in the current study. Controlling for genetics and looking at more subtle elements such as specific food components, methods of cooking, food processing and preservation, and micronutrients may be required to better understand the role of diet in the development of IBD.