Crohn's Disease: The Evidence-Based Supplement Protocol

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Crohn's disease management is driven by 5-ASAs, immunomodulators, biologic agents, and (in some patients) surgery. Supplements address the high-prevalence nutritional deficiencies that accompany the disease, plus a few adjunctive anti-inflammatory roles. All supplement use should be coordinated with the IBD team — drug interactions with immunomodulators are real.

Vitamin D — Repletion to Serum 25-OH-D 40+ ng/mL

Vitamin D deficiency is prevalent in Crohn's (60–70% of newly diagnosed adults) due to terminal ileal disease impairing absorption. Higher serum 25-OH-D is associated with reduced disease activity and reduced relapse risk in cohort data. The 2010 Jorgensen RCT in adults with quiescent Crohn's showed that 1,200 IU daily reduced relapse rate over one year. Target 40+ ng/mL; many Crohn's patients need 4,000–10,000 IU daily to maintain. See vitamin D dose guide.

EPA + DHA Omega-3, 2–3 g Daily

Omega-3 trials in Crohn's are mixed. The EPIC trials (EPIC-1 and EPIC-2) failed to show maintenance-of-remission benefit at 4 g of an enteric-coated formulation. Smaller earlier trials and cohort data suggest modest signal. Reasonable adjunct for cardiovascular and general anti-inflammatory benefit, but not a primary IBD intervention. See our omega-3 piece.

Iron — Correct Deficiency, Use IV for Active Disease

Iron deficiency anemia is the most common extraintestinal manifestation of Crohn's. Oral iron worsens active intestinal inflammation in animal models and is poorly tolerated; IV iron (ferric carboxymaltose or iron isomaltoside) is preferred in moderate-severe disease. For mild deficiency and quiescent disease, oral ferrous bisglycinate alternate-day is reasonable. See our iron recovery stack.

Vitamin B12 — Test and Replete

Terminal ileal disease or resection impairs B12 absorption. Annual serum B12 + methylmalonic acid testing. Replete with hydroxocobalamin IM weekly or high-dose oral cyanocobalamin 1,000–2,000 mcg daily. See B12 form piece.

Zinc — Repletion if Deficient

Zinc deficiency is common in Crohn's particularly during flares (15–40% prevalence). Test serum zinc; supplement 25–30 mg elemental daily with copper co-supplementation. See zinc form piece.

What NOT to Take

Avoid curcumin without IBD team input — it may interact with biologic clearance. Skip "leaky gut" supplement protocols — speculative. Avoid high-dose probiotics in active Crohn's (data is null or mildly harmful, unlike in ulcerative colitis where VSL#3 has some signal). Avoid NSAIDs entirely — they trigger flares. Don't replace 5-ASA, immunomodulator, or biologic therapy with supplements alone — disease progression risk is real.

How to Run the Protocol

Routine labs: 25-OH-D, B12, MMA, ferritin, CRP, zinc, magnesium, calcium. Replete each deficiency to target. Vitamin D ongoing at 4,000+ IU daily for most patients. IV iron during flares. B12 supplementation lifelong if ileal resection or extensive ileal disease. All of this sits underneath the disease-modifying therapy. See the broader Crohn's adjunct page.