Recommended Intake Levels

In 2000, the Food and Nutrition Board of the Institute of Medicine, National Academy of Sciences published the DRIs for vitamin C, vitamin E, selenium, and the carotenoids. Their recommendations for vitamin E appear in Table 1.

The requirements for vitamin E intakes are based primarily on long-term (5-7years) depletion and repletion studies in humans. Serum a-tocopherol concentrations and corresponding hydrogen peroxide-induced erythrocyte hemolysis were determined at various intervals. Serum concentrations necessary to prevent in vitro erythrocyte hemolysis in response known levels of vitamin E intake in subjects who had undergone experimentally induced vitamin E deficiency were used to determine estimated average requirements (EARs) for vitamin E. The recommended dietary allowances (RDAs) are levels that represent the daily a-tocopherol intakes required to ensure adequate nutrition in 95-97.5% of the population and are an overestimation of the level needed for most people in any given group.

Vitamin E Units

According to the US Pharmacopoeia (USP), 1IU of vitamin E equals 1mg all rac a-tocopheryl acetate, 0.67mg RRR-a-tocopherol, or 0.74 mg RRR-a-toco-pheryl acetate. These conversions were estimated on the relative 'biologic activities' of the various forms when tested in the rat assay for vitamin E deficiency, the fetal resorption assay. These USP IUs are currently used in labeling vitamin E supplements and food for-tificants. It should be noted that the current RDA does not use vitamin E USP units but rather the recommendation for adults is set at 15 mg of RRR-a-tocopherol or 2R-a-tocopherols. Most foods contain RRR-a-tocopherol naturally, but foods that have been fortified with vitamin E contain the synthetic form, e.g., fortified breakfast cereals. If the amount of vitamin E on the label is given in international units, then this must be multiplied by the factors given in Table 2 to obtain the amount of 2R-^-tocopherol.

Overdosage

In 2000 the Food and Nutrition Board of the Institute of Medicine, National Academy of Sciences recommended 1000 mg as an upper limit (UL) of all forms of a-tocopherol in supplements taken by adults 19 years and older, including pregnant and lactating women. ULs were set for children and adolescents by adjusting the adult limit on the basis of relative body weight. Table 3 gives the a-tocopherol UL by age group. No UL was set for infants due to lack of

Table 3 Upper limits (UL) for a-tocopherol intakes

Age (years)

UL (mgday-1)

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