Chronic inflammatory bowel diseases (IBD: Inflammatory Bowel Disease) include Crohn's disease (CD) and ulcerative colitis (UC). These are autoimmune-related diseases characterized by chronic inflammation of the gastrointestinal tract. CD can affect any part of the digestive tract (from mouth to anus), with discontinuous and transmural lesions (penetrating the entire intestinal wall). UC affects only the colon (colon and rectum), with continuous and superficial mucosal lesions. In Italy, IBD affects approximately 200,000 people, with rising incidence particularly in northern regions (similar to the epidemiological pattern of Northern Europe). IBD management includes medications (immunosuppressants, biologics), surgery in severe cases, and—as an important complementary approach—diet. There is no universal "IBD diet": the dietary approach must be individualized based on disease type (CD vs. UC), location (which part of the GI tract is affected), phase (active inflammation vs. remission), and complications (stenosis, fistulas, previous intestinal resections).

Dietary Principles During Active Inflammatory Phases

During flare periods: the primary nutritional goal is maintaining adequate caloric and protein intake despite reduced appetite, diarrhea, abdominal pain, and malabsorption. General principles during the active phase: meal fractionation (5–6 small meals daily instead of 3 large ones: reduces gastrointestinal distress), low-residue foods (limit insoluble fiber: bran, seeds, fruit and vegetable skins, raw high-fiber vegetables). Soluble fibers (pectin, inulin) are generally better tolerated. Simple carbohydrates and refined grains (during acute phases, white pasta and white rice are often better tolerated than whole grain), easily digestible foods (boiled or steamed white meats, fish, eggs, tofu, fresh cheese), limit high-risk foods that stimulate intestinal activity: dairy products (often poorly tolerated due to lactose intolerance associated with active IBD), fatty and fried foods (stimulate peristalsis), spicy and heavily seasoned foods, coffee, alcohol. Hydration: chronic diarrhea causes significant fluid and electrolyte loss. Water and electrolyte supplementation (oral rehydration solutions) is essential during flares with severe diarrhea.

Diet During Remission: Long-Term Strategies

During remission, the dietary goal is maintaining remission status, preventing nutritional deficiencies, and improving quality of life. The strongest evidence: high soluble fiber intake: during remission, adequate soluble fiber (fruits, legumes, oats, psyllium) is associated with lower recurrence risk in ulcerative colitis in multiple studies. Soluble fibers ferment in the colon producing SCFA (short-chain fatty acids: butyrate, propionate, acetate) that nourish and protect the colonic mucosa. Anti-inflammatory omega-3s: fatty fish (salmon, mackerel, sardines, herring) and fish oil supplements have documented anti-inflammatory properties. Meta-analyses show a modest but consistent effect in maintaining IBD remission, especially in ulcerative colitis. Mediterranean diet: adherence to the Mediterranean diet is associated with lower recurrence risk in IBD (observational studies: not yet randomized RCTs). The Mediterranean pattern (olive oil, fish, legumes, vegetables, fruit) combines fiber, omega-3s, and antioxidants in a seemingly protective way. Probiotics: Lactobacillus rhamnosus GG, VSL#3 (multispecies): some evidence of efficacy in maintaining UC remission. Much less data for Crohn's. Mandatory supplementation: vitamin D (deficient in most IBD patients), vitamin B12 (especially if there is ileal malabsorption in Crohn's), iron (for blood losses), zinc.

Crohn's Disease with Stenosis: Low-Residue Diet

Crohn's disease can cause stenosis (narrowing) of the intestinal lumen due to scar fibrosis. When stenosis is present, insoluble dietary fibers and bulky foods can accumulate in the narrowed tract causing intestinal obstruction (a medical emergency). Low-residue diet in Crohn's stenosis: avoid insoluble fibers (bran, fruit skins, seeds, raw fibrous vegetables), avoid volumetrically bulky foods in a single meal (small, frequent meals), prolonged cooking of vegetables (softens fibers and reduces residue), avoid tough and fibrous meat (boiled chicken, steamed fish: preferable), avoid whole dried fruit (almonds, hazelnuts: risk of impaction). The individual threshold varies greatly: some people with mild stenosis tolerate an almost normal diet, while others with significant stenosis require a strictly low-residue diet or artificial nutrition (enteral nutrition, rarely parenteral) until surgical or endoscopic resolution of the stenosis.

The Food Diary in IBD: How to Keep One

The food diary is essential in IBD because food triggers vary enormously from person to person. How to build a useful diary: for each meal, note: foods consumed with approximate quantities, meal time. Note symptoms in the following 2–6 hours: type (pain, cramping, diarrhea, bloating, gas), intensity (0–10 scale), time. Note confounding factors: daily stress, medications taken, hours of sleep, physical activity. Keep the diary for at least 2–4 weeks before drawing conclusions. Diary analysis: identify recurring patterns (foods that regularly appear before worsening), distinguish false positives (the food is blamed by coincidence, not causality), bring the diary to your gastroenterologist and dietitian for professional evaluation. Apps for IBD food diaries: GI Body Buddy, Cara Care (specific for IBD), My Symptom Tracker. Some Italian universities (Federico II Naples, Policlinico San Matteo Pavia) have specific apps for IBD patients in follow-up at their centers.

Artificial Nutrition in IBD: Indications

In some situations, oral feeding is insufficient or contraindicated in IBD. Indications for enteral nutrition (EN): severe malnutrition with inability to recover on normal food, periods of severe flare with absence of oral tolerance, pediatric Crohn's disease (exclusive enteral nutrition with polymeric formula is an induction therapy for remission equivalent to corticosteroids in children: ECCO-ESPGHAN guidelines). Exclusive enteral nutrition (EEN) in Crohn's: a meta-analysis (Cochrane, 2019) of 12 RCTs shows that exclusive EN induces remission in 60–80% of children with active Crohn's. The mechanism is debated: reduction of food antigens, microbiome modulation, direct anti-inflammatory effect of formulas. In adults it is less used due to lower adherence (formulas are organoleptically unappealing). Indications for parenteral nutrition (PN): short bowel syndrome (after extensive intestinal resections), high-output fistulas making enteral nutrition impossible, EN failure. PN is temporary therapy (or in very select cases permanent in severe short bowel syndrome) and requires specialized management.

The Microbiome and IBD: Microbiome-Targeting Diets

Alteration of the intestinal microbiome (dysbiosis) is a central feature of IBD, though it remains unclear whether it is a cause or consequence of inflammation. Dietary strategies that modulate the microbiome in IBD: FMT (Fecal Microbiota Transplantation): transplanting microbiota from a healthy donor to an IBD patient. It has demonstrated efficacy in achieving ulcerative colitis remission in multiple RCTs (remission in 30–40% of patients vs. 5–10% with placebo). The EMA approved the first standardized FMT product (Vowst) in 2023 for Clostridioides difficile, opening the door for IBD. SCD (Specific Carbohydrate Diet): a diet eliminating complex polysaccharides and disaccharides (lactose, sucrose) while allowing only easily absorbed monosaccharides. Theory: reduces foods that ferment in the colon feeding pathogenic bacteria. Pilot studies positive in pediatric Crohn's. CDED diet (Crohn's Disease Exclusion Diet): a diet specific to Crohn's that excludes animal fat, cow's milk, and processed products while including partial enteral nutrition. One RCT (Levine et al., 2019) shows efficacy comparable to exclusive EN in inducing remission in children. Currently being validated for adults.