December 2016 Issue
Digestive Wellness: Crohn's Disease
By Carrie Dennett, MPH, RDN, CD
Vol. 18, No. 12, P. 12
Helping Patients Stay Healthy With Food-Based Treatment Plans
Crohn's disease is a chronic, relapsing inflammatory bowel disease (IBD) that affects an estimated one in 500 Americans.1,2 Crohn's and other forms of IBD are autoimmune diseases, which means the immune system attacks the cells of the intestinal lining, resulting in chronic inflammation.1 Crohn's can affect the entire gastrointestinal (GI) tract, from mouth to anus, but the end of the small intestine and the beginning of the large intestine are most commonly affected. There can be normal healthy intestine in between areas of diseased tissue.1
Symptoms, which can vary based on which part of the GI tract is affected, include persistent diarrhea, abdominal pain and cramping, fever, and rectal bleeding. Loss of appetite, fatigue, and weight loss also may occur.1,3 Symptoms vary depending on the degree of inflammation present and tend to get worse over time.3 Diagnosis is based on family history, physical exam, and diagnostic tests. Other diseases with similar symptoms, including ulcerative colitis, diverticular disease, irritable bowel syndrome, and colon cancer also need to be ruled out.4
Having a parent or sibling with Crohn's increases risk, and scientists have identified more than 160 susceptibility genes for IBD.5 However, while there has been a notable increase in IBD incidence among both adults and children in the past 50 years, that increase can't be explained by genetic factors alone.5,6
As with many autoimmune diseases, it's thought that the interaction of genes, the gut microbiota, and the environment provoke the onset of Crohn's disease, which typically occurs in young adulthood.5 It appears that in genetically predisposed individuals, disruption of the gut microbiota (dysbiosis) may cause an inappropriate and uncontrolled inflammatory response.5 IBD incidence is higher in countries with a Western diet and lifestyle, and Crohn's disease in particular is more common among women, smokers, and residents of urban areas in developed countries.5-7
Treatment for Crohn's
The goal of treatment is to decrease inflammation in the intestine and prevent future flare-ups of symptoms.8 Pharmacologic therapy is the frontline treatment, which may include one or more medications to reduce inflammation or suppress the immune response. Antibiotics may be needed if infection from abscesses or fistulas is present.8
If drug therapy is unsuccessful, surgery to remove affected areas of the intestines may be necessary. However, surgery is costly, carries risks, and generally doesn't lead to long-term remission.9 This has led to a closer look at nutrition therapy, both enteral diets and manipulation of regular diets, as a treatment strategy,9 especially since patients with IBD are increasingly becoming interested in nonpharmacologic approaches to managing their disease.10
Influence of Food Components
Food components have the ability to affect both the function of the intestinal epithelial barrier and the composition of the intestinal microbiota. As understanding of the interaction between the intestinal microbiota and the immune system's inflammatory response has grown, focus has increased on the role of food in both the development and management of IBD.5,10
It's difficult to draw firm conclusions about how food choices impact Crohn's risk, but a diet high in protein and fat, from meat in particular, has been linked to elevated risk, while increased dietary fiber, especially from fruit and cruciferous vegetables, is linked to reduced risk.5,6,10-15
Prolonged, habitual intake of fast food is a risk factor for Crohn's,16 but a large prospective trial of more than 400,000 subjects found no connection between sugar, starch, or total carbohydrate and the risk of Crohn's.15 In addition, experimental studies have found that certain food additives—including modified starches like maltodextrin and emulsifiers and thickeners like carboxymethyl cellulose, carrageenan, and xanthan gum—can disrupt intestinal homeostasis.5
Evolution of Dietary Therapy
Nutrition is important not just as primary therapy and symptom management but also to prevent protein-calorie and micronutrient malnutrition, which occurs in 20% to 85% of patients.11 The best evidence for successful dietary treatment of Crohn's disease is from the use of enteral nutrition (EN). EN was originally used as supplemental nutrition for adult patients before intestinal resection surgery, but in some patients the anti-inflammatory effects of EN induced remission of Crohn's in as little as a few days, making surgery unnecessary.5
It's unclear why EN works, but proposed mechanisms include specific, positive effects on the intestinal microbiota.5,16 Both elemental and polymeric formulas tend to work equally well,5 and there's no evidence that parenteral nutrition provides any benefits over EN as primary therapy.7,11
While the exact EN formula composition doesn't appear to matter, the percentage of total calories does, with the greatest remission rates among patients who receive at least 90% of their calories from formula.17 In randomized controlled trials, exclusive EN (EEN) results in much higher remission rates than partial EN.5 Data from higher-quality studies suggest that remission rates with EEN are similar to remission rates from steroid use,5,11 but EEN does a better job of healing the intestine's muscosal lining.5
Remission rates from EEN are lower in adult Crohn's patients compared with children, most likely due to less frequent use of this protocol in adults, partly due to cost, but also because of lower adherence.5,11 Use of EN decreases quality of life, because people like to eat, and most of the formulas don't taste good. To avoid the taste, many patients opt for night feedings via nasogastric tube.16,17
Real Food Diets for Crohn's Treatment
Currently, most of the evidence on food-based treatments for Crohn's is anecdotal, with no specific diet being supported by robust data.10 Many dietary intervention trials are limited by lack of a control group.10 However, the following food-based diets are some of the more promising treatment candidates:
• Crohn's Disease Exclusion Diet (CDED). CDED combines partial EN with a strict exclusion diet that avoids dietary components hypothesized to adversely affect the microbiome or intestinal permeability such as animal fat, high sugar intake, gliadin, emulsifiers, and maltodextrin. In a pilot study of 34 children and 13 young adults with Crohn's disease, a response was seen in 78% of patients, with remission in about 70%.18 A pilot study on adult patients is planned,19 and another study is under way in pediatric Crohn's patients in longstanding remission to assess whether they remain in remission longer after stopping medications if they follow the CDED compared with patients on an unrestricted diet.20
• Specific carbohydrate diet. This diet is based on the theory that complex carbohydrates pass undigested into the colon, leading to overproduction of mucus and intestinal injury. The diet limits carbohydrates to those found in fruit, honey, yogurt, vegetables, and nuts.10 Currently, evidence based on case studies or retrospective chart review shows some promise in both pediatric and adult Crohn's, but more research is needed.21-23
• Low-FODMAP (fermentable oligo-, di-, mono-saccharides and polyols) diet. FODMAPs are highly fermentable but poorly absorbed carbohydrates and polyols. "The prevalence of IBS is much higher in patients with Crohn's disease than in healthy controls," says Patsy Catsos, MS, RDN, LD, president of the nutrition consulting firm GI Nutrition and author of IBS-Free At Last! "Many patients with Crohn's disease do report ongoing abdominal pain, bloating, excess gas, diarrhea, constipation, and other functional symptoms even when their disease is technically in remission.24 Low-FODMAP diets can help these patients improve symptom management and experience a better quality of life." Catsos points out that there are some legitimate concerns around the effects of low-FODMAP diets on the gut microbiotas of patients with Crohn's disease, such as the reduction of a few favorable bacterial species, that deserve further study.25
• Anti-inflammatory diet. In one study, an anti-inflammatory diet (IBD-AID) led to only reduction of symptoms and need for medication in eight patients with Crohn's disease, but the diet needs further evaluation through randomized clinical trials.26
• Semivegetarian diet. In one small prospective trial, patients ate a semivegetarian diet (lacto-ovo vegetarian with fish once per week and meat once every two weeks) while on drug therapy. Once they were in remission, patients were discharged and advised to continue the diet. Relapse rates at one and two years were 0% and 8% in patients who stayed on the semivegetarian diet and 33% and 75%, respectively, in patients who returned to an omnivorous diet.27
Strategies for RDs
Pending further research, there's no clearly superior real-food diet to prevent future flare-ups in established Crohn's patients. For preventing disease onset in patients with a family history of Crohn's or a personal history of other inflammatory autoimmune diseases that have been linked to dysbiosis, a diet that nourishes the gut microbiota with fiber-rich plant foods while minimizing refined sugar and carbohydrates, animal fats, and highly processed foods may be beneficial. Helping patients avoid foods that previously have caused GI distress may offer another layer of protection. Many of the diets under review for Crohn's treatment are also variations on this theme.
— Carrie Dennett, MPH, RDN, CD, is the nutrition columnist for The Seattle Times and speaks frequently on nutrition-related topics. She also provides nutrition counseling via the Menu for Change program in Seattle.
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3. Symptoms & causes of Crohn's disease. National Institute of Diabetes and Digestive and Kidney Diseases website. https://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/crohns-disease/Pages/symptoms-causes.aspx. Updated July 2016. Accessed September 16, 2016.
4. Diagnosis of Crohn's disease. National Institute of Diabetes and Digestive and Kidney Diseases website. https://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/crohns-disease/Pages/diagnosis.aspx. Updated July 2016. Accessed September 16, 2016.
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19. Pilot study of partial enteral nutrition with a unique diet for the treatment of adults patients with Crohn's disease (CDED-ADULTS). ClinicalTrials.gov website. https://clinicaltrials.gov/ct2/show/NCT02231814. Updated July 28, 2016. Accessed September 15, 2016.
20. Crohn disease exclusion diet after single medication de-escalation (CEASE). ClinicalTrials.gov website. https://clinicaltrials.gov/ct2/show/NCT02472457. Updated November 3, 2016.
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