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How Diet Impacts Risk and Outcomes for IBD

December 13, 2019

In spite of some limitations to our current knowledge of how diet affects inflammatory bowel disease (IBD), there are some key pieces of guidance that clinicians can give to their patients based on current evidence, reported James Lewis, MD, of the University of Pennsylvania in Philadelphia, at the 2019 Advances in Inflammatory Bowel Disease (AIBD) Meeting.

The research to date has strongly suggested an influence of diet on the risk of developing Crohn disease (CD) and ulcerative colitis (UC), particularly early in life. People who have high dietary intake of total fats, polyunsaturated fatty acids and omega-6 fatty acids, and meats during childhood and adolescence have a higher risk of developing both diseases later in life. At the same time, high intakes of fiber, fruits, and vegetables have been associated with decreased risk.

However, Dr Lewis noted that the implications of this research for clinical practice are low when it comes to advising adult patients who already have IBD. For these patients, there are 3 general strategies to approaching diet: using a dietary supplement, excluding a particular food or foods from the diet, or completely modifying the diet through exclusive enteral nutrition (EEN) with a formula-based diet. Because most studies of supplements have not been successful, Dr Lewis said, he focused his presentation on the other two approaches.

Formula-based therapies generally have an elemental or non-elemental source of nitrogen; variable fat content; carbohydrates consisting of glucose, fructose, and sucrose; and no or limited fiber content. These can be used as a caloric supplement (comprising less than 50% of calories), partial enteral nutrition, or EEN. Dr Lewis said studies have shown no difference in efficacy based on elemental or non-elemental nitrogen content, but because elemental formulas taste much worse, patients should be given non-elemental formulas. Remission rates for EEN have been shown to be up to 70% with no toxicity, making it an extremely effective choice of therapy. However, patients should not stay on EEN long-term for a variety of psychosocial and biological reasons.

Focus on diets using whole foods, studies with patients making adjustments in their diet consistently show self-reported improved symptoms with yogurt and rice; otherwise, there is no consistency across these studies. This poses a challenge to designing an optimal diet to improve symptoms for patients with IBD. Diverse diets have been studied, many with negative or under-powered results.

Dr Lewis cited findings from a study published earlier this year that looked at specific components of a Western diet and how they trigger the immune system. An “exclusion” diet was designed to remove all of the suspected components, specifically animal fat, wheat dairy, red meat, emulsifiers, maltodextrin, and carrageenan. At the same time, patients were encouraged to consume more fruits and vegetables. The parallel group trial compared 50% nutrition plus the exclusion diet vs EEN over the first 6 weeks, and then compared partial nutrition plus a free diet vs the exclusion diet over the second 6 weeks. Results showed comparable reductions in symptoms and C-reactive protein (CRP) levels in the first 6 weeks; however, at 12 weeks, results favored the exclusion diet on outcome measures of clinical remission, CRP levels, and sustained remission.

In summary, Dr Lewis said clinicians can advise their patients to eat Mediterranean-style diets, prepared with fresh ingredients, and higher intake of fruits and vegetables. Dr Lewis noted that this evidence may be contrary to current popular thought among clinicians that patients with IBD should avoid these foods.

—Kara Rosania


Lewis J. Rick MacDermott lecture in advanced and multidisciplinary care in IBD: diet, the microbiome, and IBD: “doctor, what should I eat for my IBD?” Presented at: 2019 AIBD Meeting; December 12-14, 2019; Orlando, FL.

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