INTRODUCTION — Inflammatory bowel disease (IBD) is an inflammatory disorder of the gastrointestinal tract manifested by symptoms such as abdominal pain, nausea, and diarrhea. These symptoms can result in loss of appetite, reduced oral intake, and ultimately, impaired nutritional status. Dietary management in IBD focuses on maximizing nutritional status, maintaining adequate intake, and avoiding foods that can exacerbate symptoms. Nutritional interventions (eg, enteral nutrition) are generally reserved for adult patients with undernutrition and IBD.
It is important to identify patients with IBD who may require nutritional intervention. Optimizing nutritional status is important to prevent long-term health consequences of malnutrition.
This topic will discuss nutrition and dietary management in adults with inflammatory bowel disease. These principles apply to patients with either Crohn disease (CD) or ulcerative colitis, but where differences exist, they are noted. Specific nutrient deficiencies in IBD, growth failure in children with IBD, and dietary risk factors for IBD are discussed separately.
●(See "Vitamin and mineral deficiencies in inflammatory bowel disease".)
●(See "Growth failure and pubertal delay in children with inflammatory bowel disease".)
Nutritional intervention and management of patients with short bowel syndrome, which can result from surgical resection for CD, is also discussed separately. (See "Management of the short bowel syndrome in adults".)
CONSEQUENCES OF MALNUTRITION — Malnutrition in patients with IBD can lead to weight loss, growth failure in children, bone disease, and/or micronutrient deficiencies.
●Weight loss and reduced muscle mass – Patients who have lost between 5 and 10 percent of their lean body mass usually have no clinical sequelae. However, loss of lean body mass beyond this threshold is associated with increased morbidity (eg, poor wound healing and higher rates of infection after surgery) [1,2].
The primary mediators of reduced muscle mass are inflammation (excessive catabolism, which accelerates protein breakdown), decreased physical activity, and/or glucocorticoid treatment [3]. Inadequate protein intake may also affect muscle mass, but this mechanism is unproven, and is not usually relevant in adults unless the deficiency is severe and prolonged (starvation).
●Bone disease – Low bone mass is common in patients with IBD, and the cause is multifactorial. Risk factors include glucocorticoid use, disease-related inflammatory activity, malabsorption, and hypogonadism. Prevention, evaluation, and treatment of bone disease in patients with IBD is discussed separately. (See "Metabolic bone disease in inflammatory bowel disease".)
●Micronutrient deficiencies – Micronutrient deficiencies in patients with IBD are discussed in detail elsewhere. (See "Vitamin and mineral deficiencies in inflammatory bowel disease".)
INCIDENCE AND EPIDEMIOLOGY — Overall, weight loss and protein-calorie malnutrition have become less common among adults with inflammatory bowel disease (IBD) during the last 30 years [4,5]. In a study of 102 adults with IBD (including 28 patients with active disease [27 percent]), seven of 50 patients with Crohn disease (CD) had malnutrition based upon body mass index (BMI) criteria [6]. Three of 52 patients (6 percent) with ulcerative colitis (UC) had malnutrition based upon BMI. For patients with CD, malnutrition was more common in those with active disease compared with inactive disease (12 versus 2 percent). However, rates of malnutrition did not differ significantly for patients with active UC compared with UC in remission (4 versus 2 percent).
CLINICAL ASSESSMENT OF NUTRITIONAL STATUS
Diagnosis of undernutrition — In our practice, the diagnosis of undernutrition is based upon our clinical impression after reviewing the following data:
●Clinical history (eg, asking about altered taste, weight loss, poor appetite, activity level and disease-specific symptoms such as nausea and abdominal pain)
●Physical examination (focusing on loss of subcutaneous fat or muscle mass)
●Body mass index (BMI)
●Dietary intake (eg, intake of solids and liquids)
Some clinicians also use a screening tool such as the subjective global assessment (form 1).
Assessment tools
●Dietary assessment – The general principles related to dietary assessment are discussed separately. (See "Dietary assessment in adults".)
As part of the dietary assessment specific to inflammatory bowel disease (IBD), we focus on disease-specific symptoms (eg, nausea, abdominal pain) that may negatively affect oral intake. We also ask patients about loss of appetite, altered taste, weight loss, and activity level.
●Physical assessment – We measure weight and calculate BMI, which can be estimated from a table or a calculator (table 1) (calculator 1). Patients with a BMI less than the 5th percentile for age or less than 18.5 kg/m2 are regarded as markedly underweight. As part of the physical examination, we subjectively assess subcutaneous fat and muscle mass.
BMI and physical examination are sufficient physical assessment tools for clinical decision-making for most patients, and additional measurements of body composition are not usually necessary.
While we do not measure skinfold thickness in routine clinical practice, these measurements can be obtained to confirm the clinical assessment. Semi-quantitative techniques for measuring body composition include triceps skin fold thickness measurements, which reflect body fat (table 2) and mid-arm cross sectional area, which, combined with skinfold thickness, reflects lean body mass. Techniques for measuring skinfold thickness in adults and children are discussed in detail elsewhere. (See "Measurement of body composition in children", section on 'Measures of body composition'.)
Methods for determining body composition in a research setting are available, including bioelectrical impedance analysis and dual energy X-ray absorptiometry [7]. Lean body mass (muscle) can also be determined by computed tomography scan using specialized software. These testing methods are discussed separately. (See "Determining body composition in adults", section on 'Research methods'.)
●Subjective global assessment tool – Global assessment tools can be used as part of nutritional assessment to identify patients at-risk for or with undernutrition. The subjective global assessment (SGA) tool takes into account multiple nutrition-related factors including functional status, dietary factors, multiple gastrointestinal-related symptoms, weight loss, and a brief physical examination (form 1) [8].
The SGA can be applied in conjunction with measuring BMI. However, in one study, patients with IBD who were well-nourished according to nutrition screening using the SGA were found to have a decrease in body cell mass (a measure of metabolically active tissues) as well as reduced handgrip strength compared with controls [9]. A separate study documented that patients with CD in remission often had a normal BMI but reduced handgrip muscle strength consistent with loss of protein muscle mass [10].
●Laboratory assessment – Laboratory monitoring of nutritional status for patients with IBD depends on the patient's disease activity, location, and nutritional status. The approach to selecting laboratory tests for specific patient groups (eg, those with active disease, those in remission) is discussed separately (table 3). (See "Vitamin and mineral deficiencies in inflammatory bowel disease", section on 'Laboratory monitoring for nutrient deficiencies'.)
While serum albumin and transthyretin (prealbumin) levels have historically been measured as part of nutritional assessment, neither is impacted by nutritional intake. These values should be evaluated in the clinical context. For example, low levels are seen in patients with active inflammation [11]. Similarly, systemic inflammation may lower levels of a specific micronutrient (eg, iron or vitamin D) in the absence of a true deficiency [5,12].
NUTRITION AND DIETARY MANAGEMENT — Measures to improve nutritional status and avoid food triggers play a role in the treatment of most patients with inflammatory bowel disease (IBD). Clinical studies in this area are small in number, often not randomized or placebo-controlled, and contain small numbers of patients. Still, there are some conclusions we can draw from this body of literature (algorithm 1).
Patients with undernutrition
Enteral nutrition — Enteral nutrition is the administration of liquid feeding into the intestine, by mouth or tube. Oral ingestion is the preferred method of delivery, although tube feedings (nasogastric or nasoduodenal) are used when oral intake does not meet daily requirements.
We use enteral nutrition supplements to increase calorie and protein intake for patients who have undernutrition and active disease but not as induction or maintenance therapy for IBD. We also use supplemental enteral nutrition for patients with undernutrition who are in remission but cannot increase caloric intake through a standard diet.
We select a specific type and quantity of enteral nutrition based on each patient’s calorie and protein requirements. Some clinicians may also consult with a dietician to coordinate individualized nutrition plans for their patients with IBD.
Liquid nutritional supplementation may take the form of a predigested (elemental or semi-elemental), or polymeric diet. Standard formulas are usually polymeric. Each consists of liquid nutrients in an easily assimilated form, differing in their protein source:
●Elemental – free amino acids
●Semi-elemental – oligopeptides
●Polymeric – whole protein
The supplement selected is usually based on clinician preference, patient tolerance, availability, and cost. The formulations of enteral nutrition and their composition are discussed separately. (See "Nutrition support in critically ill patients: Enteral nutrition", section on 'Formulations' and "Nutrition support in critically ill patients: An overview".)
The potential role of enteral nutrition as induction therapy or to maintain remission is discussed below. (See 'Patients with active disease' below and 'Supplemental enteral nutrition' below.)
Parenteral nutrition — Parenteral nutrition (PN) consists of administering calories, amino acids, electrolytes, vitamins, minerals, trace elements, and fluids via an intravenous route. In the setting of IBD, PN may be indicated for patients with short bowel syndrome, or bowel obstruction, or for patients who are unable to eat or tolerate tube feedings [13]. PN may also be used to correct nutritional deficiencies prior to surgery. The use of PN in these settings is discussed elsewhere. (See "Management of the short bowel syndrome in adults" and "Surgical management of Crohn disease", section on 'Medical optimization'.)
Patients without undernutrition
Patients with active disease — No particular food category or single food item can be broadly associated with triggering a disease flare. In our experience, patients with both irritable bowel syndrome and IBD have symptomatic improvement with a low fermentable oligo-, di-, and monosaccharides and polyols (FODMAP) diet, which is discussed separately (table 4). (See "Treatment of irritable bowel syndrome in adults", section on 'Low FODMAP diet'.)
Lactose restriction can be beneficial for some patients with active IBD. Patients who have symptoms suggestive of lactose intolerance (eg, bloating, abdominal pain and/or diarrhea following lactose ingestion) should undergo a lactose breath hydrogen test to confirm the diagnosis. Management of patients with lactose intolerance is discussed separately. (See "Lactose intolerance and malabsorption: Clinical manifestations, diagnosis, and management".)
Enteral nutrition is not a routine component of induction therapy in adults with active IBD, but may be given as an adjunct to induction therapy to patients with active disease who have undernutrition. (See 'Patients with undernutrition' above.) Enteral nutrition appears less effective than glucocorticoid therapy for inducing remission in adult patients with CD compared with conventional therapy. In a meta-analysis of eight trials including 194 adult patients with active CD, enteral nutrition was 35 percent less effective at inducing remission compared with glucocorticoid therapy (45 versus 73 percent; RR 0.65, 95% CI 0.52-0.82) [14].
An American Gastroenterological Association review of six trials including patients with active IBD concluded that parenteral nutrition given as induction therapy provided no benefit compared with placebo [15].
Patients in remission — We do not advise most patients with IBD in remission to restrict any specific food group. While some patients associate certain types and/or quantities of food (eg, high fiber diet) with development of symptoms (eg, abdominal discomfort, bloating), evidence does not link a particular food group to an increased risk of disease flare. (See 'Fiber' below.)
For general dietary advice, we agree with consensus guidance from the International Organization for the Study of IBD that advises patients with IBD to consume a diet composed of carbohydrates, fats, and protein and to limit intake of processed food (eg, sulfites) and artificial sweeteners while avoiding trans fatty acids [16]. (See "Overview of non-nutritive sweeteners", section on 'Patients who should avoid consumption of NNS' and "Dietary fat", section on 'Trans fatty acids'.)
Several nutrition and dietary interventions (eg, fiber consumption, supplemental enteral nutrition) have been studied for maintaining remission for patients with IBD, but the benefits of these are unclear.
Fiber — We do not generally advise patients in remission to restrict fiber consumption. The recommended amount of dietary fiber is 14 grams per 1000 calories, and the health benefits of dietary fiber are discussed separately (table 5). (See "Healthy diet in adults", section on 'Fiber'.)
We do advise patients who are in remission but have chronic stricturing disease (resulting in luminal narrowing and/or previous bowel obstruction) to adhere to a low fiber diet (eg, limit of 5 grams of fiber daily).
Dietary fiber should not be restricted in most patients because it may have a role in maintaining remission. Fiber has a beneficial effect on commensal gut bacteria. Some dietary fiber upon metabolism will form short-chain fatty acids, which have been shown to stimulate water and sodium absorption in the colon and to promote mucosal healing [17].
In a study of over 1100 patients with CD in remission that recorded fiber intake by quartiles, patients with highest quartile of fiber consumption were less likely to have a disease flare compared to those in the lowest quartile (OR 0.58, 95% CI 0.43-0.81) [18]. In the same study evaluating 489 patients with ulcerative colitis or indeterminant colitis, there was no association between fiber intake and disease flares.
Supplemental enteral nutrition — We do not use supplemental nutrition as primary maintenance therapy, and efficacy studies have either been inconclusive or have yielded mixed results. A systematic review attempted to look at enteral nutrition for the maintenance of remission in CD [19]. Two trials were identified that met inclusion criteria [20,21], but a pooled statistical analysis was not possible due to differences in the control interventions and outcome assessments. A prospective study failed to demonstrate the efficacy of enteral nutrition in maintaining remission in CD patients treated with infliximab [22].
In two small trials including patients with inactive CD, patients who received supplemental enteral nutrition had higher sustained remission rates compared with those on a normal diet alone [20,23]. Another small trial demonstrated that patients with inactive CD on either elemental or polymeric nutritional supplements had similar remission rates at one year [21].
Enteral nutrition in combination with biologic therapy for maintaining disease remission has also been studied. In a meta-analysis of four trials including 342 patients with CD on infliximab, patients given supplemental enteral nutrition (minimum 600 kcal daily) in addition to a regular diet had higher rates of clinical remission after one year compared with regular diet alone (75 versus 50 percent; OR 2.93; CI 1.66-5.17) [24].
Other options
Elimination diet — The term "elimination diet" can be confusing since it can refer to a restricted diet that is prescribed by a clinician as part of an evaluation or to the avoidance of one particular food. We use elimination diets when patients are convinced that there is a specific food or food group that accounts for their disease-related symptoms.
In the setting of IBD, an elimination diet may involve removing one particular food from the diet for a period of time and observing whether symptoms resolve during that time. Conversely, an elimination diet may involve introducing one new food at a time to identify foods that precipitate symptoms. Many patients can identify foods that they believe may precipitate or worsen their disease, and it is reasonable for them to avoid such foods.
One trial compared the use of glucocorticoids versus an elimination diet in 78 patients with IBD who had achieved remission with an elemental diet [25]. Patients were instructed to introduce one new food group daily and to avoid foods that they knew previously resulted in precipitating their symptoms. Relapse rates at two years were lower in the diet-treated group compared with the steroid-treated group (62 versus 79 percent, p=0.048). Food intolerances to cereals, lactose, and yeast products were common.
Probiotics — For patients with ulcerative colitis, some probiotics (eg, E. coli Nissle 1917, VSL #3) show promise, but no preparations have been validated for clinical use. For patients with CD, the available data do not support clinical effectiveness of probiotic therapy for either induction or maintenance of remission. Probiotics are living, nonpathogenic micro-organisms that, when ingested, are believed to have the potential to exert a positive influence on host health and physiology. The use of probiotics in the management of patients with IBD, including those with pouchitis, is discussed separately. (See "Probiotics for gastrointestinal diseases" and "Management of acute and chronic pouchitis".)
Other options — Several interventions (eg, low carbohydrate diets, antioxidants, fish oils) appear to have either uncertain or limited efficacy, and we do not typically use them as part of nutritional therapy for patients with IBD.
●Low carbohydrate diets — There have been anecdotal reports of a low-carbohydrate diet being helpful in preventing relapse in patients with IBD. There is no recommendation from any major healthcare society supporting this diet. One study randomized 204 patients with CD in remission to omega-3 fatty acids, a placebo, or a low-carbohydrate diet. In an intent-to-treat analysis, neither the omega-3 fatty acid supplementation nor the low-carbohydrate diet resulted in any improvement in relapse rates compared with placebo [26].
The Specific Carbohydrate Diet (SCD) is a very restrictive low-carbohydrate diet that has been promoted for multiple chronic and autoimmune diseases, including IBD, autism, and celiac disease [27]. The diet is built upon the premise that intestinal microbes that contribute to the development of IBD use carbohydrates as their primary energy source, leading to the production of acids and toxins that can injure the small intestine, further impairing carbohydrate digestion and absorption. (See "Immune and microbial mechanisms in the pathogenesis of inflammatory bowel disease", section on 'Role of microbes'.)
The SCD is grain-free, lactose-free, and sucrose-free [28]. It also limits the intake of some legumes and it does not allow for the intake of processed foods due to additives. The diet does allow for the intake of unprocessed meats, poultry, fish, eggs, honey, non-canned vegetables, some legumes, fruits, nuts, homemade yogurt, and some lower-lactose cheeses (eg, cheddar). Many patients find the diet difficult to follow due to its restrictive nature, and some clinicians express concern that it could lead to nutritional deficiencies [28].
Data on the SCD in adults with Crohn disease are limited [29,30]. In a trial including 194 patients with mild to moderate Crohn disease, there was no significant difference in rates of symptomatic remission after six weeks of adhering to the SCD compared with a Mediterranean diet (47 versus 44 percent) [29]. In addition, there was no significant difference in other outcomes such as reduction in fecal calprotectin or C-reactive protein levels. We do not use the SCD or a Mediterranean diet for treating IBD. (See "Healthy diet in adults", section on 'Mediterranean diet'.)
A diet that is low in fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) has been studied in patients with irritable bowel syndrome. Data regarding its efficacy in IBD are very limited. Two small trials have suggested that low FODMAP diet was associated with symptomatic improvement but without reducing inflammatory marker levels [31,32]. (See "Treatment of irritable bowel syndrome in adults", section on 'Low FODMAP diet'.)
Nutritional therapy for children with IBD is presented separately. (See "Overview of the management of Crohn disease in children and adolescents", section on 'Nutritional therapy'.)
●Antioxidants ‒ The data regarding the use of antioxidants for patients with IBD are not substantial enough to make a recommendation for or against them. Antioxidants are substances that neutralize oxygen-free radicals, metabolic products that are increased during inflammatory states and result in significant tissue damage. One trial of 57 patients using a combination of antioxidants as an anti-inflammatory supplement for four weeks found that treatment produced a reduction in measured indices of oxidative stress with no effect on disease activity [33].
●Prebiotics ‒ Prebiotics are nondigestible, selectively fermented carbohydrates that are thought to stimulate the growth and/or activity of a limited number of gut microbiota. However, in a trial including 103 patients with active CD who were assigned to fructo-oligosaccharides or placebo for four weeks, there was no significant difference in disease activity between the two groups [34].
●Fish oil ‒ The existing data do not support the use of fish oils for maintenance of remission in UC or CD [26,35-37]. Two large placebo-controlled trials in CD [37] and systematic reviews of clinical trials in patients with UC and CD [35,36] found that oral ingested fish oil supplementation, while safe, is ineffective for inducing or maintaining remission in either UC or CD.
Despite these results, omega-3 polyunsaturated fatty acids are potent immunomodulatory substances, and they may reduce the production of inflammatory cytokines [38].
Patients who require surgery — Patients with chronic or long-standing IBD who require surgery may have undernutrition, and optimizing nutritional status is associated with better outcomes [39]. This issue, along with the use of parenteral nutrition in surgical patients, is discussed separately. (See "Overview of perioperative nutrition support" and "Surgical management of Crohn disease", section on 'Medical optimization'.)
SPECIAL POPULATIONS
Children and adolescents — Chronic or intermittent growth failure, with associated pubertal delay, is common in children with Crohn disease (CD) and frequently reduces adult height. The evaluation and management of growth failure in children with inflammatory bowel disease (IBD) is discussed in a separately. (See "Growth failure and pubertal delay in children with inflammatory bowel disease".)
While enteral nutrition is not routinely used as induction therapy for adults with IBD, exclusive enteral nutrition is an option for induction therapy for children with CD in order to avoid using glucocorticoids. In addition, partial enteral nutrition combined with an exclusion diet may be an alternative [40]; nutritional therapy for children with CD is discussed in more detail separately. (See "Overview of the management of Crohn disease in children and adolescents", section on 'Nutritional therapy'.)
Patients who are obese — The approach to patients with obesity is similar to other patients with IBD. An overview of management of obesity in adults is discussed separately. (See "Obesity in adults: Overview of management".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ulcerative colitis in adults" and "Society guideline links: Crohn disease in adults" and "Society guideline links: Nutrition support (parenteral and enteral nutrition) in adults".)
SUMMARY AND RECOMMENDATIONS
●Patients with inflammatory bowel disease (IBD) may report symptoms such as abdominal pain and diarrhea, and these symptoms can result in loss of appetite, reduced oral intake, and ultimately impaired nutritional status. It is important to identify patients with IBD who may require nutritional intervention. (See 'Introduction' above.)
●Malnutrition in patients with IBD can lead to weight loss, growth failure, bone disease, and/or micronutrient deficiencies. (See 'Consequences of malnutrition' above.)
●For patients with IBD, we assess nutritional status by obtaining a clinical history, performing a physical examination, measuring body mass index, and assessing dietary intake. We determine if a patient has undernutrition based on those parameters, while some clinicians also use a screening tool such as the subjective global assessment (form 1). (See 'Clinical assessment of nutritional status' above.)
●For patients with IBD who have undernutrition and active disease, we use enteral nutrition supplements (given by mouth or by tube) to increase calorie and protein intake but not as induction or maintenance therapy. We also use enteral nutrition for patients with undernutrition who are in remission but cannot increase caloric intake through a standard diet (algorithm 1). (See 'Enteral nutrition' above.)
●For most patients with IBD in remission, general dietary advice includes consuming a diet comprised of carbohydrates, fats, and protein, while limiting processed foods and artificial sweeteners. We advise patients who are in remission but have chronic stricturing disease to adhere to a low fiber diet (table 5). (See 'Patients in remission' above.)
●For patients with IBD, parenteral nutrition may be indicated for bowel obstruction, short bowel syndrome, or correcting nutritional deficiencies prior to surgery.
•(See "Management of the short bowel syndrome in adults".)
•(See "Surgical management of Crohn disease", section on 'Medical optimization'.)
•(See "Overview of perioperative nutrition support".)
ACKNOWLEDGMENT — We are saddened by the death of Paul Rutgeerts, MD, who passed away in September 2020. UpToDate gratefully acknowledges Dr. Rutgeerts' work as our Section Editor for Gastroenterology.
