Vitamin E (tocopherol)
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Introduction
Vitamin E exists in eight different forms; alpha-tocopherol is the most active form of vitamin E in humans.
Daily Requirements
RDA = 15 mg/d for adult women and men (15mg = 22 IU of natural source or 33 IU of synthetic form)
Requirement increases with increased intake of PUFAs due to role of Vitamin E as an antioxidant and protected unsaturated fatty acid bonds from free radical attack.
If using supplements, examine the label: The synthetic form is labeled "D, L" while the natural form is labeled "D". The synthetic form is only half as active as the natural form.
Sources
- polyunsaturated plant oils (inc margarine)
- nuts and seeds
- eggs
- whole grains and wheat germ
Biological Roles
Redox agent
Antioxidant in lipid environments
Deficiency
Deficiencies are rare, but can result in very serious hemolytic anemia or nervous system damage, including neuropathy or myopathy (test reflexes as a screen)
Susceptible populations:
- premature infants
- people with fat malabsorption
- people on very low-fat diets
- smokers
Overdose
UL = 1000 mg/d of any form of supplemental alpha-tocopherol
Signs of toxicity include prolonged clotting time and impaired neutrophil function.
High Vitamin E supplemements or diet taken during pregnancy is associated with increased rates of congenital birth defects (Smedts et al, 2009).
Resources and References
Smedts HP et al. 2009. High maternal vitamin E intake by diet or supplements is associated with congenital heart defects in the offspring. BJOG. 116(3):416-23.
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