This study was initiated in October 1997 and conducted in two phases. The first phase of the study, which was published in 1998, focused on developing a definition for what criteria should be used to define dietary antioxidants in order to determine the selection of antioxidants to be covered in the final report.

The second phase of the study which produced the final report on nutrient values for dietary antioxidants and related compounds provided quantitative recommendations for the intake of vitamin C, vitamin E, and selenium. This phase of the study involved

1. reviewing scientific literature regarding the antioxidant nutrients and selected components of foods that may influence the bioavailability of those nutrients;
2. developing dietary reference levels of intake for the selected dietary antioxidants--levels that are compatible with good nutrition throughout the lifespan and that may decrease risk of developmental abnormalities and chronic disease;
3. addressing the safety of high intakes of these dietary antioxidants and, when appropriate, determining tolerable upper intake limits in specific population sub-groups;
4. providing guidance on appropriate uses of the recommendations and reference intakes for individuals when addressing questions of applicability to assessing intakes of populations and in formulation of appropriate dietary standards, including research needed to base such policy decisions.

Specifically, major new recommendations in this report include the following:

• The Recommended Dietary Allowance (RDA) for vitamin E and selenium is the same for adult men and women regardless of age, representing the lack of specificity in data available.
• The Recommended Dietary Allowance (RDA) for vitamin C is different for adult men and women due to women's smaller lean body mass.
• Alpha-tocopherol alone is used for estimating vitamin E requirements and recommending daily vitamin E intake, since the other naturally occurring forms of vitamin E are not converted to alpha-tocopherol in the human and are recognized poorly by the alpha-tocopherol transfer protein in the liver.
• Tolerable Upper Intake Levels (ULs) for vitamin C, vitamin E, and selenium are established.
• Research recommendations for full-scale intervention trials to test the preventive potential of vitamin C, vitamin E, selenium, and beta-carotene and other carotenoids for chronic disease are outlined. At the present time, there is no resolution of the possible impact of these nutrients or food components on chronic disease.

Further Information on DRIs