Vitamin E Conversion and Recommended Dosage
For vitamin E, 1 IU equals 0.67 mg of natural vitamin E (d-α-tocopherol) or 0.45 mg of synthetic vitamin E (dl-α-tocopherol). 1
Conversion Factors
- Natural vitamin E (RRR-α-tocopherol or d-α-tocopherol): 1 IU = 0.67 mg 1
- Synthetic vitamin E (all-rac-α-tocopherol or dl-α-tocopherol): 1 IU = 0.45 mg 1
- For IV multivitamin preparations: 1 IU = 1 mg = 1 USP unit dl-α-tocopheryl acetate 1
Recommended Daily Dosage
Adults
- Recommended Dietary Allowance (RDA): 15 mg/day for individuals ≥14 years 1
- Estimated Average Requirement (EAR): 12 mg/day for individuals ≥14 years 1
- No distinction is made between adult age categories or between sexes in the current recommendations 1
Children and Infants
- For infants and children below 11 years receiving parenteral nutrition: ≤11 mg/day 1
- For preterm infants: 2.8-3.5 mg/kg/day, not exceeding 11 mg/day 1
Important Considerations
Forms of Vitamin E
- α-Tocopherol is the most abundant form in diet and plasma, and the most biologically active form 1
- Vitamin E supplements are primarily made from α-tocopherol, often as synthetic dl-α-tocopherol or dl-α-tocopheryl acetate 1
- Natural vitamin E has approximately twice the bioavailability of synthetic vitamin E (2:1 ratio), which is higher than the previously accepted ratio of 1.36:1 2
Assessment of Vitamin E Status
- For accurate assessment of vitamin E status, especially in individuals with abnormal lipid levels, the ratio between serum vitamin E and total serum lipids should be used 1
- Deficiency is indicated by a serum vitamin E/total lipid ratio <0.8 mg/g of total lipids 1
Intake Concerns
- Over 60% of adults in the United States have vitamin E intakes below the EAR (<12 mg/d) 1
- Vitamin E was characterized as a "shortfall" nutrient by the 2015 Dietary Guidelines Advisory Committee 1
- For individuals with normal lipid absorption, fat-soluble forms of vitamin E are preferable for therapeutic and prophylactic uses 3
Safety and Upper Limits
- High-dose supplementation may interfere with normal cellular processes and increase risks of bleeding when combined with anticoagulants 4
- Some studies have linked high-dose vitamin E supplementation to adverse outcomes including increased risks of all-cause mortality, hemorrhagic stroke, and cardiovascular events 4
Clinical Applications
- Vitamin E functions as a lipid-soluble antioxidant that protects cell membranes from oxidative damage 1, 5
- It is essential for neurological function, muscle health, and maintaining erythrocyte life span 5
- In older adults, intake above currently recommended levels may improve immune and inflammatory responses and reduce risk of infectious disease 1
- Vitamin E is primarily stored in liver, skeletal muscle, and adipose tissue, with most located in mitochondrial fractions and endoplasmic reticulum 5
When prescribing or recommending vitamin E supplements, remember that the form of vitamin E (natural vs. synthetic) significantly affects the actual amount of active vitamin E received, and dosing should be adjusted accordingly.