Vitamin E
Vitamin E is a family of eight related compounds — four tocopherols and four tocotrienols. Alpha-tocopherol is the form most biologically active in humans and the one measured in blood tests. Its main role is as a lipid-phase antioxidant, protecting cell membranes from oxidative damage. Deficiency is rare in the general population; supplementation trials have been unexpectedly disappointing.
Daily requirements
- Adults: 15 mg alpha-tocopherol/day (~22 IU natural, ~33 IU synthetic).
- Pregnancy: 15 mg.
- Lactation: 19 mg.
- Tolerable Upper Intake Level: 1,000 mg/day supplemental — high-dose is associated with bleeding risk.
Natural vs synthetic
Natural vitamin E is d-alpha-tocopherol (or RRR-alpha-tocopherol) — one stereoisomer. Synthetic vitamin E is dl-alpha-tocopherol — a mixture of eight stereoisomers, of which only the RRR isomer is fully bioactive. On a per-mg basis, natural has about 1.5× the biological activity of synthetic. Both are safe; food-derived forms are best.
The failed supplementation trials
Vitamin E was one of the most heavily studied antioxidant supplements of the 2000s. Results were consistently null or slightly harmful for the general population:
- HOPE-TOO trial (n=9,541, 7 years, 400 IU/day) — no reduction in cardiovascular events; increased heart failure.
- SELECT trial (n=35,533, 5.5 years, 400 IU/day) — no cancer prevention; 17% increase in prostate cancer risk on longer follow-up.
- Miller meta-analysis (2005) — high-dose vitamin E (> 400 IU/day) associated with 4% increase in all-cause mortality.
The current consensus: do not take high-dose vitamin E supplements for prevention. Standard multivitamin doses (~30 IU) are safe.
Clinical uses of vitamin E
- Non-alcoholic steatohepatitis (NASH) — 800 IU/day slows progression in non-diabetic adults.
- Abetalipoproteinaemia and rare fat-malabsorption disorders — high-dose vitamin E prevents neurological deterioration.
- Age-related macular degeneration — vitamin E is a component of the AREDS-2 formula (400 IU) that slows progression.
Food sources
- Wheat germ oil (1 tbsp): 20 mg
- Sunflower seeds (1 oz): 7.4 mg
- Almonds (1 oz): 6.8 mg
- Sunflower oil (1 tbsp): 5.6 mg
- Hazelnuts (1 oz): 4.3 mg
- Peanut butter, spinach, broccoli, avocado — 1–3 mg per serving