adult women and 21 percent of nonsmoking adult men have dietary intakes of vitamin C that are less than the EAR for this nutrient.
Although dietary intakes of selenium depend on the selenium content of the soil where a plant was grown, adults in North America are meeting their selenium needs, probably because food in the United States and Canada is so widely distributed beyond the region where it was grown.
Only a small proportion of the adult men and women in the population reportedly has a vitamin E intake from food and supplements greater than the EAR. However, estimates of vitamin E intake are particularly difficult due to a propensity to underreport fat intake which results in its underestimation (dietary fat serves as the major carrier for vitamin E). In addition, the EARs for vitamin E are based on α-tocopherol only and do not include amounts obtained from the other seven naturally occurring forms of vitamin E (β-, γ-, δ-tocopherol and the four tocotrienols). Because the various forms of vitamin E cannot be interconverted in humans, EARs, RDAs, and AIs apply only to intake of the 2R-stereoisomeric forms of α-tocopherol from food, fortified foods, and multivitamins. Currently, most nutrient databases, as well as nutrition labels, do not distinguish among the various tocopherols in food. They often present the data as α-tocopherol equivalents and include the contribution of all eight naturally occurring forms of vitamin E, after adjustment for bioavailability (e.g., γ-tocopherol is usually assumed to have only 10 percent of the availability of α-tocopherol). 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-tocopherol equivalents is greater than the intake of α-tocopherol alone. Based on NHANES III dietary intake data, approximately 80 percent of the α-tocopherol equivalents from food are from α-tocopherol, and thus can contribute to the body's requirement for vitamin E.
Data for intakes of vitamin C, vitamin E, and selenium from food and supplements in the United States are provided in this report. Data from Canada are available only for vitamin C from food. Detailed data for intakes of carotenoids from a recently released and expanded food composition database in the United States are presently being analyzed and are not available to be included in this report. Thus they will be included in the Appendix of a subsequent DRI report that will include vitamin A.