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VAST Study Team, 1993; Loyd-Puryear et al., 1991; Rahmathullah et al., 1990; Salazar-Lindo et al., 1993; West et al., 1991).

An EAR of 300 μg RAE/day can be calculated based on the dark adaptation data obtained from 13 individuals from four studies on adults (Table 4-4). The duration of depletion and repletion varied among these four studies and the majority of the studies were conducted on men. Interpolation of the level of vitamin A at which dark adaptation of each individual was corrected in these four studies results in a median intake of 300 μg RAE/day, which can be used to set an EAR based on dark adaptation for adults. Using this method, there was insufficient evidence to support setting a different EAR for men and for women, as there were too few women studied. EARs using dark adaptation as the indicator for children (1–3 years, 112 μg RAE/day; 4–8 years, 150 μg RAE/day; 9–13 years, 230 μg RAE/day) and adolescents (14–18 years, 300 μg RAE/day) are based on extrapolation from the adult EAR as described in Chapter 2.

INTAKE OF VITAMIN A

Food Sources

Common dietary sources of preformed vitamin A in the United States and Canada include liver, dairy products, and fish. Chug-Ahuja et al. (1993) reported that carrots were the major contributor of β-carotene (25 percent). Other major contributors to β-carotene intakes included cantaloupe, broccoli, squash, peas, and spinach. Carrots were also the major contributor (51 percent) of α-carotene. Fruits were the sole contributors of β-cryptoxanthin. According to data collected from the 1994–1996 Continuing Survey of Food Intakes by Individuals (CFSII), the major contributors of vitamin A from foods were grains and vegetables (approximately 55 percent), followed by dairy and meat products (approximately 30 percent).

Dietary Intake

The Third National Health and Nutrition Examination Survey (NHANES III) (Appendix Table C-8) estimated that the median dietary intake of vitamin A is 744 to 811 μg/day for men and 530 to 716 μg/day for women using the new provitamin A carotenoid conversion factors for calculating retinol activity equivalents (RAE) (see Table 4-3). When one examines Appendix Table C-8 to determine the proportion of individuals with intakes that were less than the EAR (500 μg RAE/day for women and 625 μg RAE/day for men), it



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