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Crohn’s disease is a type of inflammatory bowel disease (IBD) that is associated with alterations in the gut microbiome (defined as the collective genomes of bacteria, bacteriophage, fungi, protozoa and viruses living inside the gastrointestinal system). Crohn’s disease is believed to arise from a shared interaction between genetic and environmental influences, such as dietary patterns (Raman, 2020).

Crohn’s disease most commonly occurs in the small intestine and the colon. It can affect any part of your gastrointestinal (GI) tract, from gum (mouth) to bum (anus), and can involve some parts of the GI tract while skipping others. The range of severity for Crohn’s is mild to debilitating, depending on a number of factors. Symptoms vary and can change over time. In severe cases, the disease can lead to life threatening flare-ups and complications. There has been a steady rise in new cases of IBD over the past several decades with the highest prevalence rates seen in Europe and North America of approximately 0.3% of the population (Holland, 2021).

What causes Crohn’s disease, and what are the treatment options?

The recent increase in incidence of Crohn’s disease across newly industrialized countries suggests environmental factors induce or modify the disease. This has occurred in parallel with global dietary shifts towards a more “Western” style of eating. In addition to the external environment, other factors influencing the chances of developing Crohn’s are the immune system, and the genetic background of an individual. In fact, up to 20 percent of people with Crohn’s disease also have a parent, child, or sibling with the disease, according to the Crohn’s and Colitis Foundation of America (Abdalla, 2017).

Certain factors can affect the severity of a patient’s symptoms, including whether they smoke, their age, whether or not the rectum is involved, and the length of time they’ve had the disease (Cosnes, 2012).

Common medical therapies include corticosteroids, immunomodulatory and biologic agents, and surgery. However, these therapies are not universally effective – the disease may recur and drugs may not always be effective. More recently, guidelines have included dietary therapies as a treatment option (Raman, 2021).

What is the correlation between dietary patterns and Crohn’s disease?

Research has long explored the link between diet and the quality of life for a patient with Crohn’s disease, however, diet guidelines for IBD treatment have been lacking until recently. Dr. Maitreyi Kothandaraman (Dr. Raman) is a gastroenterologist, and an Associate Professor at the University of Calgary.  She is also the director of the university’s Clinician Investigator Program (CIP) and the Medical Director of Alberta’s Collaboration of Excellence for Nutrition in Digestive Diseases (ASCEND). Her research alongside her colleagues has helped explore the nutritional and dietary requirements for chronic gastrointestinal conditions.

Dr. Maitreyi Kothandaraman

Dietary interventions and gut microbial compositions

A recent study investigated by her team explores the relationship between patterns of dietary intake and gut microbiota in Crohn’s disease patients, and examined the effects of a dietary intervention in patients consuming a non-diversified diet. The study was a success, showing that specific dietary patterns are associated with specific gut microbial compositions in patients with Crohn’s disease. Perhaps more importantly, it was revealed that a diet intervention in patients consuming a non-diversifed diet can successfully modify the gut microbial composition to resemble that of a patient who is eating a diversified diet. Essentially, it is never too late to change, and a simple switch in diet can change a person’s gut microbial composition to lessen the impact and symptoms of Crohn’s (Raman, 2020).

Dietary patterns and changes in inflammation

Another study by Dr. Raman and her colleagues looked at very specific dietary patterns, food groups, and nutrients in Crohn’s disease, and how they are associated with inflammation. They looked at a group of individuals with Crohn’s disease in remission over the course of 3 months. Dietary patterns, diet components and nutrients were correlated with measures of inflammation. Fecal calprotectin (FCP) was used to measure gastrointestinal inflammation, and C-reactive protein (CRP) measured systemic inflammation. These proteins are called surrogate markers of inflammation, and are used to measure the effect of a specific treatment (which is dietary alterations, in this case). The results of the study were significant – increased daily servings of leafy green vegetables was associated with a lower FCP level, and thus a decrease in GI inflammation. Additionally, an optimal omega-6 to omega-3 fatty acid ratio, of 8:1, lead to a lower CRP levels, and thus less systemic inflammation. Overall, the study found that a diet rich in fruit, vegetables, and fish contributed to a lower incidence of IBD (Raman, 2020).

Dietary patterns and nutrient deficiencies

Since individuals with Crohn’s disease are encouraged to limit their intakes of certain foods to avoid complications and flare-ups, this can often lead to nutrient deficiencies if not monitored carefully. Dr. Raman and her peers conducted a survey to explore the macro- and micro- nutrient intakes and dietary patterns of patients with Crohn’s disease. Compared with the representative sample (which is a group of healthy individuals without Crohn’s disease), patients with the disease had similar energy, protein, carbohydrate, and total fat intake. Conversely, intake of polyunsaturated fats (omega-6 and 3) and monounsaturated fats were lower in patients with Crohn’s (which is not ideal), while dietary fibre was higher. As for micronutrients, vitamins C, D, thiamin, niacin, magnesium, phosphorus, zinc, and potassium were all significantly lower in all patients with Crohn’s disease when compared to the representative sample. This vitamin deficiency can be attributed to both a lack of intake in diet, as well as the inability to absorb nutrients properly within the gastrointestinal system (Raman, 2018).

Woman eating a salad in a restaurant.

Dietary patterns and types of interventions

Dr. Raman and her colleagues reviewed the findings of multiple studies in an article they published in 2019 and found similar patterns. High school students who followed a dietary pattern characterized by higher fruit, vegetable, and fish intake were 50% less likely to develop ulcerative colitis, another inflammatory bowel disease, while high-sugar and soft drink intake combined with low intake of vegetables was associated with an increased risk of colitis. They also reviewed numerous different treatment options that were based on introducing a dietary plan to a group of people with Crohn’s. Elimination diets such as Crohn’s Disease Exclusion Diet, Autoimmune Protocol Diet, Specific Carbohydrate Diet, and the Semi-Vegetarian Diet were all found to have varying levels of success in either getting a subject into remission, or keeping them there (Raman, 2019).

Which dietary path is right for each person?

As with any significant changes to a person’s diet, they should be implemented under the close supervision of a physician and ideally a registered dietician. It is abundantly clear that there is a key role of both long-term diet as well as short-term dietary changes on the structural and functional composition of the gut microbiome, which directly reflects the incidence and severity of Crohn’s disease and inflammatory bowel diseases. Knowing this, a dietician can help you figure out which options are best suited to your individual needs.


Abdalla, M. 2017. Prevalence and Impact of Inflammatory Bowel Disease-Irritable Bowel Syndrome on Patient-reported Outcomes in CCFA Partners.

Cosnes, J. 2012. Factors affecting outcomes in Crohn’s disease over 15 years.

Holland, K. 2021. Understanding Crohn’s Disease.

Raman, M. 2021. Dietary patterns, food groups and nutrients in Crohn’s disease: associations with gut and systemic inflammation.

Raman, M. 2020. A Diversified Dietary Pattern Is Associated With a Balanced Gut Microbial Composition of Faecalibacterium and Escherichia/Shigella in Patients With Crohn’s Disease in Remission.

Raman, M. 2019. Diet in Treatment of Inflammatory Bowel Diseases.

Raman, M. et al. 2018. Cross-Sectional Analysis of Overall Dietary Intake and Mediterranean Dietary Pattern in Patients with Crohn’s Disease.