HEALTH NEWS

Study Title:

Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids

Study Abstract

This report provides quantitative recommendations for the intake of vitamin C, vitamin E, and selenium. It also discusses β-carotene and other carotenoids (α-carotene, β-cryptoxanthin, lutein, lycopene, and zeaxanthin) but does not provide quantitative recommendations for their intake. It is one volume in a series of reports that presents dietary reference values for the intake of nutrients by Americans and Canadians. The development of Dietary Reference Intakes (DRIs) expands and replaces the series of Recommended Dietary Allowances (RDAs) in the United States and Recommended Nutrient Intakes (RNIs) in Canada. The report includes current concepts about the roles vitamin C, vitamin E, selenium, and β-carotene and the other carotenoids play in long-term health, going beyond a review of the roles they are known to play in traditional deficiency diseases. A major impetus for the expansion of this review is the growing recognition of the many uses to which RDAs and RNIs have been applied, and a growing awareness that many of these uses require the application of statistically valid methods that depend on reference values other than recommended nutrient intakes.

The overall project is a comprehensive effort undertaken by the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (DRI Committee) of the Food and Nutrition Board, Institute of Medicine, the National Academies, with active involvement of Health Canada. (See Appendix A for a description of the overall process and its origins.) This study was requested by the Federal Project Steering Committee for Dietary Reference Intakes (see Appendix B for membership), which is coordinated by the Office of Disease Prevention and Health Promotion of the U.S. Department of Health and Human Services, in collaboration with Health Canada.

Major new recommendations in this report include the following:

A definition of a dietary antioxidant is provided.
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.
α-Tocopherol alone is used for estimating vitamin E requirements and recommending daily vitamin E intake, since the other naturally occurring forms of vitamin E (β-, γ-, and δ-tocopherols and the tocotrienols) are not converted to α-tocopherol in the human and are recognized poorly by the α-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 β-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.