Dietary Interventions in Crohn's Disease

Pre-illness dietary habits may increase the risk for developing Crohn’s disease in susceptible individuals.¹⁹⁴ Research has demonstrated high sugar and carbohydrate intakes significantly impact the development of inflammatory bowel disease. While researchers did not differentiate between Crohns Disease and Ulcerative Colitis, both di- and monosaccharide consumption increased the risk of developing IBD in general.¹⁹⁵ Sucrose was consistently associated with increased risk for IBD, and the trend was statistically significant in Crohn's Disease patients. Patients with IBD had a significantly lower intake of fruit, fiber, and vegetables. Another study confirmed a higher intake of total carbohydrates, starch, and refined sugars in 104 patients, immediately prior to diagnosis of Crohn's Disease.¹⁹⁶ A population-based, case-controlled Swedish study examining 152 Crohn's Disease cases found a significant 3.4-fold increase in relative risk for developing Crohns Disease with consumption of fast food 2-3 times weekly.¹⁹⁷

Once Crohn’s disease has manifested, dietary disturbances result from significant loss of appetite and contribute to weight loss and nutrient deficiencies. Dietary rehabilitation of Crohn's Disease patients depends on the extent of disease, presence of intestinal stricturing, obstruction, or short bowel (due to surgery), and ability to consume food orally.¹⁹⁸ When strictures, obstruction, or short bowel are present it may be necessary for the patient to use enteral nutrition.

Enteral and Parenteral Nutrition

Enteral nutrition involves the provision of liquid-formula diets by mouth or tube into the gastrointestinal tract.¹⁹⁹ It is suggested that partial bowel rest, a restoration of nutritional status, and a reduction in immunological stimulation caused by whole protein can induce remission.

Parenteral nutrition, administering of nutrients by a route other than the alimentary canal (e.g., intravenously, subcutaneously), is now seldom used for Crohns Disease treatment, except in the most extreme cases involving significant impairment of absorption or intestinal obstruction.²⁰⁰

Several diets of potential benefit to Crohn's Disease patients are administered enterally, but all include protein, carbohydrates, electrolytes, vitamins, and minerals. In elemental diets the protein source is from amino acids or short-chain peptides; such diets were once considered the best form of enteral feeding.²⁰¹ Polymeric diets containing whole protein have a higher energy:osmolarity ratio than elemental diets and have been shown to be especially beneficial in treating children with Crohns Disease.²⁰² Oligopeptide diets contain short-chain peptides of 4-5 amino acids.²⁰³ Numerous studies have compared the benefits of enterally-fed elemental and polymeric diets to steroid therapy for Crohn’s disease (Table 7).^204-209 The results are varied, with some showing elemental diets superior to steroids and vice versa. In general it can be concluded, at least in the short-term, that an oral elemental diet is at least as effective as steroids in achieving or maintaining remission of mild-to-moderately active Crohn's Disease in adults. Because of the potentially devastating effects of steroid therapy in growing children, enteral dietary therapy is almost always recommended as a first-line treatment.^210,211

In certain countries, epidemiological data show an association between high dietary intakes of omega-6 polyunsaturated fatty acids (PUFAs) and increased rates of Crohn’s disease.²¹² The role of fatty acids in inflammation is well established and several studies have examined the therapeutic benefit of different types and amounts of dietary fat in nutritional therapy. Fish oil studies are discussed below. Regarding other types of fats, research indicates enteral feeds or other diets low in fat are more effective in treating Crohns Disease patients and maintaining remission than diets high in fat.²¹³ There is also some evidence that fat type can impact the effectiveness of enteral nutrition. Due to its proinflammatory effect, high amounts of linoleic acid (an omega-6 essential fatty acid) in an elemental diet would be expected to show less benefit, a conclusion supported by a meta-analysis conducted by Middleton et al.²¹⁴ Conversely, Gassull et al found an enteral diet high in linoleic acid and low in oleic acid actually resulted in better patient remission rates (52%) than a high oleic acid/low linoleic acid diet (20%). The use of medium-chain triglycerides (MCTs) in varying amounts has also been studied. MCTs in enteral nutrition do not seem to show any detriment or benefit over long-chain triglycerides, regardless of amount used.²¹⁵

Dietary Fiber

The results of studies investigating the beneficial effects of fiber in Crohn’s patients are inconclusive. In an Italian study, 70 Crohn's Disease patients were randomly assigned to follow a low-residue diet or a normal Italian diet for 29 months. No difference in outcome was observed in the two groups, and a lifting of dietary restrictions did not result in symptom exacerbation.²¹⁶ In a second, controlled trial in which 20 Crohn's Disease patients were given an unrefined carbohydrate, fiber-rich diet or an exclusion diet (of foods they were intolerant to), 70 percent (7 of 10) of patients on the exclusion diet remained in remission for six months compared to zero percent (0 of 10) at six months on the unrefined carbohydrate, fiber-rich diet.²¹⁷

In one study, 162 patients with active Crohns Disease were assigned to a diet unrestricted in sugar and low in fiber, and were compared to 190 active Crohn's Disease patients given a low-sugar, high-fiber diet. Patients were followed for approximately two years. Assessment via history, physical exam, and laboratory testing revealed no significant differences between the two treatment groups, indicating the high-fiber diet did not benefit patients with active Crohn’s.²¹⁸ In another study 32 patients with Crohn's Disease were placed on a fiber-rich diet in addition to conventional treatment. Another 32 matched Crohn's Disease patients acted as controls and received no specific dietary instruction. After 52 months the treatment group had significantly fewer and shorter hospitalizations and required less intestinal surgery than the control group.²¹⁹

Elimination Diets

Research on elimination diets in Crohn's Disease has yielded inconclusive results. Elimination diets are difficult to follow with high drop-out rates and patients seem to have difficulty in identifying foods that trigger symptom exacerbation. Food sensitivities often are not persistent and are difficult to validate with subsequent blinded challenge. Remission rates in Crohns Disease patients on elimination diets do not appear to be significantly better than those observed in patients on unrestricted diets.²²⁰



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