Editing Nutrition (section)

=== Fat-Soluble Vitamins (A, D, E, K) ===

Fat-soluble vitamins are stored in the liver and adipose tissue, so deficiency develops slowly and '''toxicity is possible''' with megadoses. Absorption depends on bile and pancreatic lipase, so patients with fat malabsorption, cholestasis, cystic fibrosis, or bariatric surgery are at risk of deficiency.

{| class="wikitable"
! Vitamin !! Key function !! Deficiency !! Food sources
|-
| A (retinol) || Vision, epithelial integrity, immunity || Night blindness, xerophthalmia, dry skin || Liver, egg yolk, dairy, orange and dark green vegetables (beta carotene)
|-
| D (calciferol) || Calcium and phosphorus absorption, bone mineralization || Rickets in children, osteomalacia and osteoporosis in adults || Fortified milk, fatty fish, egg yolk, sunlight exposure
|-
| E (tocopherol) || Antioxidant, protects cell membranes || Hemolytic anemia (notably in preterm infants), neuropathy || Vegetable oils, nuts, seeds, wheat germ
|-
| K || Synthesis of clotting factors II, VII, IX, X, and proteins C and S || Bleeding, prolonged PT/INR || Green leafy vegetables, broccoli, Brussels sprouts; also made by gut flora
|}

'''Nursing application (high yield):''' Patients on warfarin should keep vitamin K intake '''consistent''', not eliminated. Wildly varying green vegetable intake destabilizes the INR. A sudden large salad increases vitamin K and lowers the INR, raising clot risk; abruptly stopping greens raises the INR and bleeding risk.

'''Nursing application:''' Prolonged broad-spectrum antibiotic therapy kills vitamin K-producing gut flora and can prolong the PT/INR. Newborns receive intramuscular phytonadione (vitamin K) at birth because the gut is sterile and stores are low.