tocopherol

Vitamin E (tocopherol) is one of four fat-soluble vitamins (A, D, E, K) and is absorbed via micelles requiring bile and pancreatic enzymes, then transported in chylomicrons. It functions primarily as a lipid-soluble antioxidant, neutralizing free radicals and preventing peroxidation of polyunsaturated fatty acids in cell membranes, working synergistically with selenium (a cofactor for glutathione peroxidase).

Deficiency: Rare in adults due to adequate dietary intake and body stores, but occurs in conditions of fat malabsorption (e.g., cystic fibrosis, cholestatic liver disease, abetalipoproteinemia) or in premature infants with low fat stores. Clinical manifestations include: - Hemolytic anemia due to increased RBC membrane fragility from lipid peroxidation (particularly in premature infants) - Neurologic deficits resembling spinocerebellar ataxia: degeneration of posterior columns (loss of proprioception/vibration sense) and spinocerebellar tracts (ataxia), along with peripheral neuropathy and areflexia - Skeletal muscle myopathy

Toxicity: Excess vitamin E intake (common with supplementation) can inhibit vitamin K-dependent clotting factor synthesis, increasing bleeding risk, especially in patients on anticoagulants like warfarin.

Clinical associations for boards: Vitamin E deficiency is classically tested in the context of malabsorptive syndromes and abetalipoproteinemia (due to inability to form chylomicrons/transport lipids). It's also relevant in premature infants receiving high oxygen therapy, where vitamin E supplementation helps prevent retinopathy of prematurity by reducing oxidative damage.

Dietary sources: Vegetable oils, nuts, seeds, and green leafy vegetables.