Animal-based foods: Clams, sardines, beef liver, tuna, salmon, dairy, and eggs, are highest

may cause iron-deficiency anemia Nausea and vomiting particularly with stricturing disease/obstruction Urgency and tenesmus with rectal/colonic involvement Weight loss and malnutrition due to malabsorption, food avoidance, elevated metabolic demand Fever with active inflammation, abscess, or fistula Perianal disease fissures, fistulae, skin tags, abscesses Extraintestinal Manifestations Arthropathy peripheral or axial (enteropathic arthritis, M07.6x) Dermatologic: Erythema nodosum (L52), pyoderma gangrenosum, psoriasis (L40.5) Ocular: Uveitis/iritis (H20.01), episcleritis, scleritis Hepatobiliary: Primary sclerosing cholangitis (K73.2), fatty liver, cholelithiasis Metabolic: Osteopenia/osteoporosis (from steroid use and malabsorption), nephrolithiasis Hematologic: Anemia (iron deficiency, B12/folate deficiency, anemia of chronic disease) When a patient with Crohns disease is admitted with significant weight loss, malnutrition, or protein-calorie deficiency , query the provider to specify the degree of malnutrition (mild, moderate, severe protein-calorie malnutrition)

"Cobalamin metabolism and its clinical aspects" (PDF)
PMC 3650358
It works systemically to support regeneration throughout the body, including skin tissue that has been compromised by aging, sun exposure, or injury