Definition 

Chronic inflammatory bowel diseases – Crohn's disease (CD) and ulcerative colitis (UC) are increasingly common, with a rising incidence worldwide. They are characterized by an alternation of acute episodes and phases of remission. The etiology is not fully understood. Environmental influences, genetics and the intestinal microbiome are postulated. Malnutrition can occur in both conditions but is particularly significant in Crohn's disease, as it can affect the entire gastrointestinal tract. In contrast, ulcerative colitis is confined to the large intestine, with fewer direct malabsorptive effects.  ²

 
Impact on nutritional status 

Malnutrition in IBD results from several factors: reduced oral intake, increased nutritional demands, greater gastrointestinal losses, a reduced absorptive surface, and interactions between medications and nutrients. The degree of malnutrition varies depending on disease activity, duration, extent, and particularly the degree of inflammation, which increases catabolism and decreases appetite. 

Nutrient requirements of patients with inflammatory bowel disease. Adjustments should be made based on the patient's nutritional status, physical activity, and age. Adjusted body weight (ADJ) is used from a BMI of 28, otherwise, the body weight prior to hospital admission applies. BW = body weight; d = day. 

Vitamines, Minerals und Trace elements

• Coverage of daily requirements: routine supplementation with multivitamin products, even in remission
• Caution vitamin C content ≤200 mg/d; high vitamin C content promotes hyperoxaluria and kidney stones
• Calcium: 1x/d in case of active disease under glucocorticoid therapy
• Fat-soluble vitamins A, D, E, and K in case of steatorrhea

Aims of nutritional therapy

• Maintaining/improving nutritional status and body function 
• Prevent malnutrition/nutrient deficiencies 
• Support remission maintenance, reduce disease activity, and minimize the need for surgery 
• Prevent osteoporosis 
• To identify malnourished patients early, a Nutritional Risk Screening should be performed at least twice a year. 

Energy and protein requirements should be met with oral nutrition whenever possible. If less than 75% of needs are covered with enrichment, snacks, or oral sip feeds, enteral nutrition should be introduced within five days. Complementary parenteral nutrition is indicated if less than 75% of needs are met by oral and/or enteral nutrition. 
 
There is no single "IBD diet" that can universally promote remission in patients with active disease or during remission. However, affected patients should receive individualized nutritional counseling and therapy tailored to their specific needs by a specialized nutrition therapist as part of a multimodal treatment approach. Malnutrition and unnecessary dietary restrictions should be avoided at all costs. 

Oral Nutrition

Generally better tolerated and has stronger evidence for Crohn's disease. 
No exclusive diet recommended; elemental diets (due to high osmolarity) are not first-line therapy. 
Oral sip feeds are the first step when nutritional therapy is indicated, serving as a minor supportive measure alongside normal food.

Possible Diets

CDED (Crohn’s Disease Exclusion Diet)

• For active (mild to moderate) CD if partial enteral nutrition (PEN) is not possible or desired.
• + Includes fruits, vegetables, white meat, simple and resistant starches.
• - Avoids animal and saturated fats, red meat, gluten-containing grains, emulsifiers, and maltodextrins.
• Can be implemented with or without partial enteral nutrition.

Levine Diet (Israeli Diet, also known as ModuLife® 1) = A combination of CDED + PEN

• + Encourages whole food nutrition with fresh, unprocessed foods high in soluble fiber, resistant starch, proteins, and other nutrients. 
• - Avoids components that negatively affect the microbiome, intestinal barrier, or immunity (e.g., animal fats, dairy products, emulsifiers, gluten). 
• Phase 1: 6 weeks - five mandatory foods (chicken breast or lean fish, eggs, potatoes, bananas, apples) with a limited list of permitted foods (e.g., rice, avocado, tomato) + 50% energy from Modules® IBD. 
• Phase 2: 6 weeks - building on Phase 1, with increased dietary fiber + 25% energy from Modules® IBD. 
• Phase 3: At least 9 weeks - no restrictions on quantity or specific prescribed foods. 

Specific Carbohydrate Diet (SCD)

• For active (mild to moderate) CD. 
• Includes only monosaccharides (glucose, fructose, galactose), proteins, and fats. 
• + Primarily fresh fruits, vegetables, meat, yogurt, nuts, and hard cheese. 
• - Avoids grains (wheat, barley, corn, rice), processed/canned foods, and milk. 

Mediterranean Diet

• For active (mild to moderate) CD in adults.
• Emphasizes fruits, vegetables, moderate whole grains, protein from fish, poultry, beans, and olive oil as the main fat source.

Low-FODMAP (Low Fermentable Oligosaccharide, Disaccharide, Monosaccharide And Polyol)

• FODMAPs are short-chain carbohydrates that are incompletely absorbed in the small intestine and can trigger bloating and diarrhea.
• Recommended for inactive CD and UC patients with functional gastrointestinal symptoms (such as IBS).
• Involves strict reduction of all FODMAPs for 2–4 weeks, followed by gradual reintroduction based on symptoms or tolerance.
• Not suitable for long-term therapy due to potential adherence issues, particularly during extended reintroduction phases.

Practical Tips (if indicated)

• Avoid or reduce intake of red meat, high-fat diets (saturated fats, trans fats, polyunsaturated omega-6 fatty acids), emulsifiers (such as carrageenan, carboxymethylcellulose, polysorbate 80), and inorganic microparticles (additives in processed foods). 
• Promote a diet rich in plant-based whole foods, high in fiber, and with polyunsaturated omega-3 fatty acids. 
• Aim for a normal weight; weight reduction should only be attempted in stable remission phases. Note: Overweight and obesity may be associated with a poorer response to biologic therapies. 
• Avoid smoking. 
• For CD patients with secondary lactose intolerance (present in approximately 30%): follow a lactose-free diet. 
• For hyperoxaluria: adopt a low-fat and high-calcium diet, as hyperoxaluria is often associated with fat malabsorption. 
• For chronic strictures: follow a low-fiber diet (<5 g/day) or consider a diet with adapted texture, or distal (post-stenotic) enteral nutrition in patients with strictures or stenosis and obstructive symptoms. 
• Patients treated with ion exchange resins, such as cholestyramine, have minimal risk for fat malabsorption and do not differ nutritionally from other CD patients. 

Enteral nutrition

When oral feeding is insufficient, tube feeding should be considered as supportive therapy. Enteral nutrition is preferred due to its trophic effect on the intestinal mucosa, maintenance of bowel function, prevention of bacterial translocation, positive effects on mucosal cytokine profile, and reduction of inflammation.

For CD patients with low-output distal fistulas (ileum or colon), nutrition can usually be provided via the enteral route (typically as food).

Exclusive Enteral Nutrition (EEN)

• Standard EE (polymeric, moderate fat, no specific additives) can be used as primary and supplemental nutrition therapy for active disease. 
• First-line therapy in pediatrics for remission induction in active (mild to moderate) CD 
• Adults: Data are less conclusive (lower tolerance, especially with extended EEN). Most centers use steroids (or biologics) as first-line therapy 
• However, there is a high recurrence rate after resumption of an undifferentiated oral diet. 
• Not effective in UC. 
• Example: Modulen® IBD for 4–12 weeks, administered orally and/or via a feeding tube. 

Partial Enteral Nutrition (PEN)

• Better tolerated than EEN
• CDED + Modulen® IBD (which contains TGF beta as a trophic factor)
• For active (mild to moderate) CD
• Provides 50-25% of calories (step-down approach) from tube feeding, with the remainder from whole foods consumed orally.

Parenteral Nutrition (PN)

PN is indicated in IBD when:

1. There are absolute contraindications to oral/enteral nutrition.
2. Oral or enteral nutrition is insufficient (e.g., in cases of gastrointestinal tract functional disorders or in CD patients with short bowel syndrome).
3. Bowel obstruction prevents the placement of a feeding tube or when attempts to place one have been unsuccessful.
4. Other complications arise, such as an anastomotic leak or a proximal/high-output fistula.

Monitoring

Micronutrient deficiencies (check at least once a year)

Iron status, vitamins B6, B9 (folic acid), B12, D; calcium, magnesium, selenium, zinc. Possibly additional (for severe forms): vitamins B1, C, E, K, copper. Caution: When interpreting blood values, it is important to consider that many are acute-phase reactants , with serum levels that may rise or fall due to the inflammatory response. 

• Anemia: blood count initially every 3 months, if stable every 6-12 months. After correction of iron deficiency, check iron levels every 3 months for at least 1 year.
• Ferritin cut-offs for diagnosing iron deficiency (with CRP assessment): 
• Without inflammation < 30 μg/L; 
• With inflammation <100 μg/L + transferrin saturation < 20% 
• Oral iron as first-line therapy for mild anemia in patients in remission 
• Max. 100 mg elemental iron p.o. every 2 days in the morning on an empty stomach; if insufficient, supplement parenterally
• Intravenous iron as first-line therapy for patients with
• Active disease 
• Intolerance to oral iron 
• Hemoglobin level <100 g/L 
• Use of erythropoiesis-stimulating agents 
• Folic Acid (Vitamin B9) 
• in case of deficiency: Acidum folicum 5 mg 1x/d for 2 weeks, then 2x/week, level control after 3 months and, if necessary, discontinuation-test with consecutive level control 
• Therapy with sulfasalazine/methotrexate: 5 mg once a week (24-72h after methotrexate) 
• Vitamin B12
• Prophylactic 1 g parenteral per month if distal ileum resection >20 cm
• For deficiency: 1 g intramuscularly every other day for a week, then once a month.
• Zinc
• Burgerstein Zinc Gluconate 30 mg once daily, taken 1 hour before or 2 hours after a meal for 2-3 weeks 
• Caution with Timing: Zinc impairs the absorption of iron/copper while calcium/folic acid impairs the absorption of zinc. 

IBD patients with active disease and those on steroid therapy

Serum calcium and 25(OH) vitamin D levels should be monitored and supplemented as necessary to prevent low bone mineral density. Osteopenia and osteoporosis should be managed according to current osteoporosis guidelines. 

Fluid balance and urinary sodium in patients with severe diarrhea or high-output jejuno-/ileostomy

Fluid intake should be adjusted accordingly (reduce hypotonic fluids and increase saline solution), considering any food intolerances that may increase fluid loss. Parenteral infusions (fluid and electrolytes) may be required if stoma output remains high. 

CD patients 

Dehydration should be avoided to minimize the risk of thromboembolism. In patients with interrupted food intake for several days, be vigilant for signs of refeeding syndrome. 

Special considerations 

Physical exercise should be encouraged in all IBD patients, with a focus on weight training twice a week and cardio training for 30 minutes three times a week, as sarcopenia is common. 

Perioperative phase 

ERAS protocols should be applied for most elective surgeries. For emergency surgeries, malnourished patients or those unable to resume oral nutrition within 7 days post-surgery should receive artificial nutrition (EN or PN). Patients not meeting their energy and/or protein needs through regular food should be encouraged to use oral sip feeds. If additional support is needed beyond normal food and sip feeds, EN should be provided during the perioperative period. 

In cases of malnutrition, IBD surgery should be postponed for 7–14 days if feasible, using this time for intensive artificial nutrition. EN should be prioritized over PN; however, if more than 60% of energy needs cannot be met by EN alone, a combination of EN and PN should be considered. 
 
PN should generally be used as a supplement to EN in the perioperative period for IBD patients. PN alone should be reserved for situations where EN is not feasible (e.g., lack of access, severe vomiting or diarrhea) or is contraindicated (e.g., bowel obstruction, ileus, severe shock, bowel ischemia), high-output fistula, or severe intestinal bleeding. Early nutritional support should be provided to surgical CD patients, as it reduces postoperative complications, regardless of the delivery method. 
 
In CD patients with chronic gastrointestinal failure (such as those with short bowel syndrome following resection), PN is essential and often life-saving, at least initially. Most IBD patients can resume regular food intake or EN early in the postoperative phase. In the immediate period after a proctocolectomy or colectomy, water and electrolyte administration are essential to maintain hemodynamic stability. 

Medications/Supplements 

• Specific formulations or substrates, such as glutamine and omega-3 fatty acids, are not recommended in enteral or parenteral nutrition (EN or PN) for IBD patients. 
• Probiotics should not be used to treat active disease. However, Escherichia coli Nissle 1917 or the probiotic blend VSL#3 can be considered to induce remission in mild to moderate ulcerative colitis (UC), but not in Crohn’s disease (CD). 
• For patients with a pouch following colectomy and who suffer from pouchitis, probiotics such as VSL#3 may be beneficial if antibiotic therapy has failed. 

The probiotic mixture VSL#3 can also be used for both primary and secondary prevention of pouchitis in UC patients who have undergone colectomy with pouch-anal anastomosis.