The dietary selenium intakes in the United States and Canada have been estimated in several studies. A detailed evaluation of diets consumed by 22 Maryland residents (using direct selenium analysis) indicated that selenium intake was 81 ± 41 (SD) lag (1.0 ± 0.5 µmol)/day (Welsh et al., 1981). The Food and Drug Administration analyzed food items purchased in different regions of the United States over the period 1982 to 1991 and calculated dietary selenium intake from those results (Pennington and Schoen, 1996). The median calculated intake was 87 µg (1.1 µmol)/day with a range of 79 to 104 µg (1.0 to 1.3 µmol)/day in different years. These results support those of the Maryland study generally, but do not provide an indication of the extremes of selenium intake in the United States.

The Third National Health and Nutrition Examination Survey (NHANES III) intake data (Appendix Table C-6 and Table C-7) reported higher median selenium intakes of 106 µg (1.3 µmol)/day from food and 108 µg (1.4 µmol)/day from food and supplements for all individuals based on dietary recall and food tables, but this method has low accuracy as discussed earlier. Selenium intake in Canada has been reported to be somewhat higher than U.S. intake, 113 to 220 µg (1.4 to 2.8 µmol)/day (Thompson et al., 1975).

Dietary intake of selenium varies tremendously among different populations. Factors that affect the intake include the geographic origin of the food items and the meat content of the diet. The lowest selenium intakes are in populations that eat vegetarian diets consisting of plants grown in low-selenium areas. Selenium-deficient Chinese populations live in low-selenium areas and are generally too poor to eat meat or to purchase food grown in other regions. Dietary intake of selenium in the United States and Canada varies by region but is buffered by the food distribution system. Thus, extensive transport of food throughout Canada and the United States prevents low-selenium geographic areas from having low dietary selenium intakes.

Drinking water has been analyzed in the United States and several countries and does not supply nutritionally significant amounts of selenium (Bratakos et al., 1988; NRC, 1980a; Robberecht et al.,

Front Matter (R1-R23)

Summary (1-20)

1 Introduction to Dietary Reference Intakes (21-34)

2 Vitamin C, Vitamin E, Selenium, and •-Carotene and Other Carotenoids: Overview, Antioxidant Definition, and Relationship to Chronic Disease (35-57)

3 Vitamin C, Vitamin E, Selenium, and •-Carotene and Other Carotenoids: Methods (58-72)

4 A Model for the Development of Tolerable Upper Intake Levels for Nutrients (73-94)

5 Vitamin C (95-185)

6 Vitamin E (186-283)

7 Selenium (284-324)

8 •-Carotene and Other Carotenoids (325-382)

9 Uses of Dietary Reference Intakes (383-400)

10 A Research Agenda (401-408)

A Origin and Framework of the Development of Dietary Reference Intakes (409-412)

B Acknowledgments (413-415)

C Dietary Intake Data from the Third National Health and Nutrition Examination Survey (NHANES III), 1988–1994 (416-431)

D Dietary Intake Data from the Continuing Survey of Food Intakes by Individuals (CSFII), 1994–1996 (432-437)

E Canadian Dietary Intake Data, 1993, 1995 (438-439)

F Serum Values from the Third National Health and Nutrition Examination Survey (NHANES III), 1988–1994 (440-457)

G Options for Dealing with Uncertainties (458-462)

H Glossary and Acronyms (463-468)

I Biographical Sketches of Panel and Subcommittee Members (469-482)

Index (483-506)