Vitamin E (tocopherols, tocotrienols)

Vitamin E is a family of eight fat-soluble molecules — four tocopherols (α, β, γ, δ) and four tocotrienols (α, β, γ, δ) — sharing a chromanol ring but differing in their tail: tocopherols carry a saturated phytyl chain, tocotrienols an unsaturated isoprenoid chain with greater membrane mobility. The liver retains α-tocopherol via α-TTP, making it the dominant circulating form and reference standard. Its principal role is chain-breaking antioxidation: α-tocopherol donates a hydrogen atom to lipid peroxyl radicals, halting oxidative chain reactions and protecting membrane polyunsaturated fatty acids. Vitamers also suppress the NF-κB pathway, modulate Nrf2, and influence gene expression in cholesterol synthesis and apoptosis. Dietary sources — wheat-germ oil, sunflower seeds, almonds, avocado — are linked in observational data with lower mortality; a 30-year ATBC cohort analysis found serum α-tocopherol inversely associated with all-cause mortality. High-dose supplementation differs: Miller et al. (2005; 19 RCTs, >135,000 participants) found a dose-dependent mortality increase above ~150 IU/day. The SELECT trial (Klein et al., 2011; ~35,000 men) found α-tocopherol raised prostate cancer incidence 17% versus placebo (HR 1.17; 99% CI 1.004–1.36). Tocotrienols — γ and δ forms in particular — are under investigation for neuroprotective and anti-senescence effects, but human trial data remain limited; co-administered α-tocopherol may suppress their bioavailability. Evidence supports meeting vitamin E needs through food over high-dose supplements.