Diet & Nutrition
If you have Crohn's disease and feel exhausted no matter how much sleep you get, you're not imagining it. Up to 85% of people with Crohn's have at least one nutritional deficiency, and the symptoms often mimic or amplify the disease itself: fatigue, brain fog, muscle weakness, bone pain, and slow wound healing. The tricky part is that Crohn's doesn't cause deficiencies in a single, predictable way. Where your disease is located, which medications you take, and whether you've had surgery all shape your unique nutritional risk profile. Knowing what to test for and how to replenish effectively can change how you feel day to day.
Why Crohn's Creates Nutritional Gaps
Crohn's disease disrupts nutrition through several overlapping mechanisms. Inflammation in the gut wall reduces your ability to absorb nutrients from food, even when you're eating well. Active disease often suppresses appetite and causes nausea, making it harder to eat enough in the first place. Diarrhea accelerates the loss of electrolytes and minerals like zinc, magnesium, and potassium. And some of the medications used to manage Crohn's contribute their own depletion patterns: methotrexate interferes with folate metabolism, while corticosteroids reduce calcium absorption and accelerate bone loss.
Surgical resections compound the problem further. If you've had a portion of your ileum removed, you lose the specific absorption site for vitamin B12 and bile salts. Without adequate bile salts, your body struggles to absorb fat-soluble vitamins (A, D, E, and K). Extensive resections can lead to short bowel syndrome, where the remaining intestine simply can't keep up with nutritional demands.
Which Deficiencies to Test For Based on Disease Location
One of the most useful things you can understand about Crohn's nutrition is that your disease location predicts your deficiency pattern. This information can help you and your gastroenterologist prioritize the right lab work.
Ileal and ileocolonic disease affects the terminal ileum, where vitamin B12 is exclusively absorbed. Research shows that B12 deficiency prevalence reaches 33% in Crohn's patients, with ileal resection length being an independent risk factor. Ileal inflammation also impairs bile salt reabsorption, leading to deficiencies in fat-soluble vitamins D, A, E, and K. Calcium absorption depends heavily on vitamin D, so these deficiencies cascade: low vitamin D leads to poor calcium uptake, which over time contributes to bone loss. As many as 30% to 60% of people with Crohn's or ulcerative colitis have lower-than-average bone density.
Colonic disease is more commonly associated with iron deficiency. Chronic inflammation in the colon causes microscopic blood loss and impairs iron absorption. Anemia affects roughly 70% of people with Crohn's at some point, with iron deficiency as the leading cause. Folate deficiency is also more common in colonic disease, particularly if you take sulfasalazine, which acts as a folate antagonist.
Extensive or upper GI disease can cause broader malabsorption affecting zinc, selenium, magnesium, and B vitamins. Reduced serum zinc and selenium occur in about 50% of patients even during inactive disease, making these worth monitoring regardless of how well you feel.
The Lab Tests to Request
Knowing which labs to ask about gives you more agency in your care. The European Crohn's and Colitis Organization (ECCO) recommends screening with a complete blood count, serum ferritin, and C-reactive protein every three months during active disease and every six to twelve months during remission. Beyond those basics, consider discussing the following tests with your care team based on your disease pattern:
For ileal disease: serum B12 (or the more sensitive methylmalonic acid and holotranscobalamin tests), vitamin D (25-hydroxyvitamin D), calcium, and a fat-soluble vitamin panel
For colonic disease: iron studies (ferritin, transferrin saturation, serum iron), folate, and a complete blood count to screen for anemia
For all Crohn's patients: zinc, selenium, magnesium, and vitamin D, since these deficiencies are common regardless of disease location
Standard B12 blood tests can miss early deficiency. A study found that conventional testing identified B12 deficiency in only 5% of Crohn's patients, but that number jumped to 32% when researchers used more sensitive markers like holotranscobalamin and methylmalonic acid. If you have ileal disease and your standard B12 comes back "normal" but you still feel fatigued, ask about these additional tests.
How to Replenish Effectively
Supplementation strategies for Crohn's differ from general population advice because gut absorption is compromised.
Iron presents a particular challenge. Oral iron supplements are an option during remission, but they commonly cause GI side effects and may worsen intestinal inflammation. For active disease or when oral iron isn't tolerated, intravenous iron is the preferred approach. The ECCO guidelines recommend 500 to 1,000 mg of IV iron for patients with symptomatic iron deficiency. Getting your Crohn's under better control also helps, since reducing mucosal inflammation slows GI blood loss and improves iron levels on its own.
Vitamin B12 supplementation depends on the extent of ileal damage. If you've had significant ileal resection, oral B12 may not be absorbed adequately, and intramuscular injections or high-dose sublingual forms become necessary. Your gastroenterologist can determine the right route based on your surgical history and lab values.
Vitamin D and calcium work together and should be addressed as a pair. The Crohn's & Colitis Foundation recommends 1,500 mg of calcium daily and 800 IU of supplemental vitamin D for IBD patients at risk of bone loss. Your doctor may recommend higher vitamin D doses if your levels are significantly low. A DEXA scan to assess bone density is worth discussing if you've used corticosteroids long-term or have extensive small bowel disease.
Folate supplementation is straightforward for most patients, typically 1 mg daily, and is especially important if you take methotrexate or sulfasalazine.
Zinc, selenium, and magnesium can often be addressed through a high-quality multivitamin formulated for absorption, though individual supplementation may be needed if levels are significantly depleted. Since zinc losses increase with diarrhea, pay extra attention during flares.
Enteral Nutrition as a Therapeutic Tool
Enteral nutrition, where a liquid formula provides all or most of your calories, is an underused strategy in adult Crohn's care. While it's well established as a first-line treatment in pediatric Crohn's, research shows it can also be effective for adults. A prospective study found that exclusive enteral nutrition led to full clinical remission in 80.5% of adult participants after 12 weeks, with mucosal healing in nearly half.
Exclusive enteral nutrition (EEN) works by resting the gut while delivering complete nutrition in an easily absorbed form. For adults, adherence can be the biggest barrier since consuming only a liquid formula for weeks is demanding. Partial enteral nutrition, where a formula supplement covers a portion of your daily calories alongside a limited food diet, offers a more sustainable middle ground. Studies suggest that maintenance enteral nutrition combined with medical therapy may prolong remission and reduce relapse rates.
If you're recovering from a flare, losing weight, or preparing for surgery, ask your gastroenterologist whether enteral nutrition could help bridge the gap while your gut heals.
Practical Weight and Hydration Management
Unintended weight loss is one of the most visible signs of Crohn's-related malnutrition, and regaining weight while managing an inflammatory bowel condition requires a different approach than simply "eating more."
Focus on calorie-dense, easy-to-digest foods during active symptoms. Nut butters, avocado, olive oil added to meals, and well-cooked root vegetables deliver calories without requiring large volumes of food. Oral nutritional supplements providing 250 to 300 extra calories per day, enriched with vitamins and micronutrients, can support weight recovery when appetite is limited. Protein shakes designed for medical nutrition can also help, though it's worth choosing formulas without artificial sweeteners or high-fiber additives that might trigger symptoms.
Dehydration compounds every other nutritional problem. Frequent diarrhea depletes fluids and electrolytes rapidly. Sipping water throughout the day, salting your food, and using oral rehydration solutions during flares are basic but effective strategies. Watch for signs like dark urine, dizziness, dry mouth, and muscle cramps, all of which signal you need to increase your fluid intake.
Working With an IBD-Specialized Dietitian
A registered dietitian who specializes in inflammatory bowel disease can help you build a nutrition plan tailored to your specific disease pattern, medications, and surgical history. The Crohn's & Colitis Foundation recommends looking specifically for a registered dietitian nutritionist (RDN) rather than a general nutritionist, since RDNs have clinical training and credentialing that nutritionists may not.
To find one, start by asking your gastroenterologist for a referral, contacting your local hospital's nutrition department, or searching the Academy of Nutrition and Dietetics directory. Some IBD centers offer multidisciplinary visits where you see your GI doctor and a dietitian in the same appointment, which makes coordinating care much easier.
Keeping a food journal that tracks what you eat alongside your symptoms gives a dietitian the data they need to identify patterns and adjust your plan. Over time, this record becomes a powerful tool for understanding which foods work for your body and which don't.
Building Your Nutritional Recovery Plan
Nutritional recovery with Crohn's is not a one-time fix. It's an ongoing process that shifts as your disease activity changes, your medications are adjusted, and your body heals. The most important step is getting baseline lab work that reflects your actual risk profile, not just a standard panel. From there, work with your care team to build a supplementation strategy that accounts for your disease location, absorption capacity, and current symptoms.
Track your lab results and energy levels in Aidy to catch nutritional deficiencies early and see how supplementation affects your symptoms over time.