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DRI DIETARY REFERENCE INTAKES FOR Vitamin C, Vitamin E, Selenium, and Carotenoids
not distinguish among all the different forms of vitamin E (Figure 6-1) in food. These databases often present the data as α-tocopherol equivalents (α-TE) and thus include the contribution of all eight naturally occurring forms of vitamin E, after adjustment for bioavailability using previously determined equivalencies (e.g., γ-tocopherol has been usually assumed to have only 10 percent of the availability of α-tocopherol) based on fetal resorption assays. This report (see Chapter 6) recommends that the use of α-TE be abandoned due to the lack of evidence of bioavailability via transport in plasma or tissues. Because these other forms of vitamin E occur in foods (e.g., γ-tocopherol is present in widely consumed oils such as soybean and corn oils), the intake of α-TE is greater than the intake of α-tocopherol alone.
All α-tocopherol in foods is RRR-α-tocopherol, but the all rac-α-tocopherol in fortified foods and supplements is an equal mix of the 2R- and 2S-stereoisomers. The EARs, RDAs, and AIs given in Chapter 6 apply only to the intake of the RRR-α-tocopherol from food and the 2R-stereoisomeric forms of α-tocopherol (RRR-, RSR-, RRS-, and RSS-α-tocopherol) that occur in fortified foods and supplements (see Chapter 6, Figure 6-2). The UL applies to all eight stereoisomeric forms of α-tocopherol that occur in fortified foods and supplements.
Conversion Factor for Vitamin E in Food and Supplements
The reported median vitamin E intake in the United States of all individuals surveyed in the Third National Health and Nutrition Examination Survey (NHANES III) was 9 mg (21 µmol)/day of α-TE (see Appendix Table C-3). Additional data from the NHANES III database indicate that α-tocopherol contributed 7 mg/day of the 9 mg/day median intake of total α-TE from food (see Appendix Table C-4). Thus, based on NHANES III, approximately 80 percent of the α-TE from foods in the survey are reported to be contributed by α-tocopherol. So to estimate the α-tocopherol intake from food surveys in the United States in which food intake data are presented as α-TE, the α-TE should be multiplied by 0.8.
mg of α-tocopherol in a meal = mg of α-tocopherol equivalents in a meal × 0.8.
In addition, the amount of chemically synthesized all rac-α-tocopherol compounds added to foods and multivitamin supplements in milligrams should be estimated at 50 percent to calculate