Chapter 32, Ep 3 of 4: Fat-Soluble and Water-Soluble Vitamins

Episode three reads the vitamins the way the boards test them, where every micronutrient produces a stereotyped phenotype that is the recognition cue on a stem. Behind each cue is a biochemical mechanism, and the same mechanism predicts the at-risk population and the replacement strategy. Memorizing the symptom list is the wrong frame; learning the mechanism lets the phenotype, the population, and the treatment fall out of it. The fat-soluble vitamins share a bile-salt absorption requirement, and the water-soluble vitamins carry the acute decisions, thiamine before glucose and B12 before folate.   Topics covered Bile-salt requirement for fat-soluble vitamins Vitamin A night blindness and toxicity Vitamin D metabolic bone disease Vitamin E neuropathy, hemolysis, and NASH Vitamin K, warfarin, and the NPO patient Essential fatty acid deficiency Thiamine and Wernicke encephalopathy B12 absorption steps and pernicious anemia B12-versus-folate masking trap   Key decisions Anything that disrupts the enterohepatic bile-acid cycle, cholestyramine, cholestasis, ileal disease, cystic fibrosis, or unsupplemented parenteral nutrition, deletes all four fat-soluble vitamins plus essential fatty acids. Chronic vitamin A intake above roughly fifty thousand international units per day activates hepatic stellate cells into myofibroblasts and produces perisinusoidal fibrosis and portal hypertension, while a single large dose instead causes pseudotumor cerebri. Vitamin E at eight hundred international units daily improves histology only in non-diabetic biopsy-proven NASH, and extension beyond that phenotype is unsupported given increased prostate cancer and hemorrhagic stroke risk at high doses. An NPO patient on warfarin started on broad-spectrum antibiotics spikes the INR within days because both dietary and colonic bacterial vitamin K sources are eliminated at once. Medium-chain triglyceride oil cannot prevent essential fatty acid deficiency because its eight-to-twelve-carbon chains lack the eighteen-carbon backbone, so intravenous lipid emulsion one to two times weekly is required. Thiamine must precede any glucose load in an at-risk patient, given empirically as five hundred milligrams intravenously three times daily, because glucose without thiamine precipitates Wernicke encephalopathy. Always check B12 before starting folate, because high-dose folate corrects the megaloblastic anemia while subacute combined degeneration of the cord progresses unchecked.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected]. (00:00) - Deficiencies as recognition cues (01:02) - The fat-soluble bile-salt requirement (02:44) - Vitamin A: night blindness and toxicity (04:54) - Vitamin E: neuropathy, hemolysis, and NASH (06:23) - Vitamin K, warfarin, and the NPO patient (09:38) - Thiamine and Wernicke encephalopathy (11:33) - B12 absorption in four steps (13:52) - The B12-versus-folate masking trap